First grow problem – Edges of leaves are curling up?

Question: What do I do if the edges of my cannabis leaves are curling up?

Take a look

Only one of my 3 plants is having this issue.

A friend suggestted that the issue may be low humidity.

I live in a dry area so the humidity in my house is normally below 20%. However, when I checked the humidty in my grow tent, it was 36% so I’m not actually sure it’s actually too low.

Any ideas of anything else I should check?

More grow details: 250W HID, 2x3x5 grow tent with 4″ inline fan. Northern Lights strain. Seeds germinated in rockwool and transplanted into 4 gallon smart pots w/ mix of peat moss and perlite. Fox Farms Nutrient Trio for nutes – following the dosing schedule but started with 1/2 doses for the first week. pH of water is 6.5-6.6 and runoff from pots tested at 6.4-6.6.

Answer: Heat stress, Root Problems or Extreme Humidity

This looks like the result of excessive heat, root problems (possibly from overwatering) and/or suffering from extreme humidity levels (such as very high or low humidity).

When the the serrated edges of marijuana leaves curls or tipped up like that, it’s often a sign of temperature stress, overwatering/root problems or extreme humidity levels. This plant was overwatered and living in high heat, which is what caused these symptoms.

When the problem is low humidity, the leaf will also often fold in the middle, like a taco.

What’s your temperature in your grow area? Is there a hot spot around these plants from the grow light?

You mentioned that this is happening to only some of your plants. If this is happening to the plants which are closest to your grow light, that’s a hint that the problem may be temperature related.

If your light is simply too close, you can move the bulb further away from these plants and this issue may resolve itself. However, these leaves are showing symptoms of heat stress, without light stress (burning / spotting), so it’s more likely that the light is a good distance away and the heat just isn’t being controlled properly.

If plants are also droopy, it’s likely you’re dealing with watering or root problems.

When growing with hot HID lights, good ventillation and an exhaust fan will go a long way towards preventing all these problems. If the whole grow area is too hot with stagnant air, you will want to consider venting out all that extra heat.

Having good air movement, like a small fan in your grow tent blowing over the tops of your plants, can help prevent hot spots from forming directly under your grow lights.

In general, if it’s too hot for you to be comfortable, it’s too hot for your plants.

Learn More About Cannabis Heat Stress

Learn More About Root Problems

Learn About Controlling Humidity

Jump to…

Leaf tips turned down? It may be a Nitrogen Toxicity
How to Set Up / Vent Heat with HID Grow Lights
Check These 7 Things & Cure 99% of Marijuana Growing Problems
1st Grow in My Garage – Auto Northern Lights in Grow Box Under 400W HPS

Why are the outer edges of my plant’s top leaves starting to curl?

A:

There are several possibilities regarding what could be causing your curling leaves. Curled leaves that are not accompanied by any necrosis or browning of the foliar edges may be attributable to nutrient excess, insect damage, water, other cultural issues, or even possibly the genetics of your plant.

There is no way to give you a definitive answer without having some background information, but we can cover some of the most likely possibilities.

Not enough water can cause this symptom, but if it does not correct itself after a good drink, this is not likely the issue.

Conversely, the leaves of an oversaturated plant may curl or droop, but often this is followed by a yellow and or sick appearance of the plant too. Too much water and poorly drained soil may also set the stage for root rot, which will cause the leaves and ultimately the entire plant to collapse.

If you are growing these plants in containers or planting beds and not hydroponically, make sure that the media you are growing in is well-drained and porous so that excess water can drain through. A moisture meter can help to identify how wet your media is and whether or not this may be the cause.

Too much nitrogen to the point of toxicity can cause curling leaves as well. Performing a simple soil or media analysis will help to rule this possibility out or in depending on your results.

Your plant may also just be showing signs of stress due to cultural factors. Is the curling just on one side? This could be an environmental problem due to continual and proximal exposure to a fan.

Another likely culprit that can be easily checked and remedied is if you are growing these plants in pots and if they have become root-bound. If this is the case, scuff up the roots and pull them away from the root ball before transplanting them into a larger container.

If none of these seem to be the cause of the leaf curl that you are experiencing, the symptoms may be caused by a mite infestation.

Several different species of mites, including Broad mites, Cyclamen mites, and Russet mites may be feeding on your plant leaves and leave curled leaves in their wake as a result of a substance that they inject into the foliage while feeding.

Generally, though, there will be other symptoms appearing shortly after you notice the curling such as a change of color (yellow to brown) or a speckled appearance to the leaves.

If you have ruled out all of the above, there is possibility that the particular species of plant that you are growing has the naturally tendency to have curled leaves. This is not an unknown characteristic of some strains of plants.

Leaf Curl On Bird Of Paradise Plants: Why Do Bird Of Paradise Leaves Curl?

Bird of paradise is one of those other-worldly plants that combine fantasy with spectacle. The brilliant tones of the inflorescence, uncanny resemblance to its namesake and towering huge leaves make this plant a stand out in the landscape. In unfavorable sites and conditions, you may notice curling leaves on bird of paradise. There are several reasons for leaf curl on bird of paradise. Here are a few to help you narrow down why do bird of paradise leaves curl.

Why Do Bird of Paradise Leaves Curl?

The natural form of bird of paradise is as a 5- to 30-foot tall tree. There are several varieties but each one has huge paddle shaped leaves that start out as curled tubes from the main body. The leaves unfurl as they mature, but even older foliage will bear some curve at the edges. Bird of paradise is a tropical plant with 18-inch long leaves on average that grows out of a main crown in a clump. A little bit of leaf curl on bird of paradise is normal but occasionally there

will be more pronounced curvature and possibly other damage signs.

Cultural Causes of Leaves Curling on Bird of Paradise Plant

The bird of paradise is suitable for USDA plant hardiness zones 10 and 11. It is not reliably hardy in zone 9, but you can grow it in a pot in cooler zones in summer as long as you move it indoors before cold temperatures arrive. The leaves are thin at the edges and tend to tatter in high winds or with repeated bruising. Any number of things can cause leaf curl on bird of paradise in improper conditions.

  • New plants need plenty of water at establishment or their newer leaves will curl in protest.
  • Chilly temperatures tend to make the leaves curl inward as protection.
  • Poor soil and improper soil pH will also present as curling leaves on bird of paradise.

Leaves Curling Up on Bird of Paradise Due to Pests and Disease

Several pests have been known to attack bird of paradise plants. Malformed leaves and curling foliage are caused by sucking insects such as scale and mites. A form of thrip, Chaetanaphothrips signipennis, is commonly found on bird of paradise plants and also causes the leaves to curl.

Some fungal diseases are common to the bird of paradise; but while they do cause foliar deformation, they do not commonly cause leaves curling up on bird of paradise. More common reasons are environmental.

Curling Leaves on Bird of Paradise Indoors

Container bound bird of paradise plants should be repotted every few years or when they become pot bound. New soil is important in container plants to help provide nutrients. It is also important to give the plant enough root space. If the plant is root bound, it impedes its ability to uptake moisture and nutrients which can cause curling leaves on bird of paradise.

Situating the plant near a drafty window will affect leaf health as will allowing the container to dry out for too long. Leaves may also curl after a transplant, but they will usually rally in a few days after the transplant shock wears off.

How To Treat Bay Pests : Dealing With Pests On A Bay Tree

Bay trees seem remarkably resistant to most pests. Perhaps it’s the pungent oil in the aromatic leaves. In the case of sweet bay, the leaves are often used in recipes, which means that treating pests on a bay tree requires organic, food safe methods. Most bay tree insects are foliar feasters, but there are a few boring insects that can cause damage to the trunk and twigs. Read on to find out how to treat bay pests in a safe and non-toxic manner.

About Bugs That Eat Bay Leaves

Bay laurel is a remarkably adaptable temperate zone plant. It has few disease or pest issues and is easy to cultivate. There are few bugs that eat bay leaves, in part because of their intense foliar oil. Most pests on a bay tree will be boring or sap sucking, favoring the stems and woody parts of the plant. Some are easy to spot, while others almost require a microscope. Dealing with bay tree pests starts with figuring out which insect is offending the plant. Then control measures can come into play as you get your tree back into perfect health.

The primary foliar pests on bay trees are aphids and psyllids. Aphids are soft bodied insects that may be brown, black, white, green or even red. They cling in colonies to stems or leaves, often in a clustered mass. These insects suck sap and can eventually cause leaf stippling and low vigor in the entire plant.

Similarly, psyllids are sap sucking tiny insects. You are more likely to spot them by their cast off waxy exoskeletons. Both types of insect secrete honeydew, a sticky substance which may cause sooty mold. The mold coats the leaves and reduces the plant’s ability to gather solar energy and respirate.

Use neem oil for treating bay tree pests of this type. Spray it onto all parts of the plant using the formula on the bottle. Occasionally, thrips can also attack leaves. These are difficult to spot but should respond to neem treatments as well.

Other Pests on a Bay Tree

Boring insects cause damage by tunneling in the xylem or vascular tissue of the tree. Adults are small brownish black beetles, but it is the larvae which do the most damage. Larvae tunnel in the smaller woody tissue of the plant and eat plant tissue, while adults tunnel simply to lay the eggs. Leaves, twigs and entire branches wilt and die. The activity can resemble blight, a common disease. In most cases, pesticides are not required. Simply prune off damaged shoots and twigs as they occur. Keep plant debris away from the base of the tree where adults can overwinter.

Scale is another pest of bay trees. These armored or soft insects look like a scab on tree bark. They are also sucking insects which feed on both leaves and woody material. Eventually, the tree will weaken and growth slows. Leaves yellow and die and twigs have a scorched appearance.

How to Treat Bay Pests on Culinary Plants

It is important not to use toxic substances on trees whose leaves you use in recipes. Neem oil is a safe alternative to most commercial pesticides. It comes from the neem tree and is organic.

Pruning of damaged plant material slows pest advancement while good cultural care enhances plant health so it can withstand small invasions of a pest. Provide adequate water, drainage and nutrients. Prune to open the canopy of the plant, increasing air flow and allowing predatory insects access. There are also, several biological controls such as lady beetles, which will feed on insect pests. Lacewings and parasitic wasps may also be helpful in combating bay pests.

In small plants, soak a cotton ball in alcohol and rub it on infected twigs and leaves. This will kill the pests but not harm the plant. Often, simply hosing off the pests is the most effective and easiest solution. Treating bay tree pests can be completely safe and successful without the use of damaging chemical formulas.

Bay Tree Pests and Diseases

Bay trees are tender evergreens with leathery lance-like leaves. The dried leaves are widely used as a seasoning for soups and stews. They are a component of the herbal “bouquet garni,” which is a bundle of herbs added to flavor a simmering soup stock. The several varieties of bay trees are relatively pest and disease free, but are susceptible to attack by insects. Most of these can be successfully eradicated with consistent treatment until the infestation has passed.

Scales

Scales are insects that appear as brown-colored bumps on the stems and twigs of bay trees. They exude a sticky substance which adheres to the leaves and surfaces beneath the tree. Treat by applying rubbing alcohol with a cotton swab to the scales. Follow-up by spraying with rubbing alcohol at 10-day intervals until the infestation is gone.

Aphids

Aphids are small white insects that suck on the juices of the plants. They concentrate on the leaves, stems and small twigs and can completely defoliate an untreated plant. Spray infected bay trees with insecticidal oil, following the manufacturer’s directions.

Laurel Wilt

Laurel wilt is caused by a non-native beetle, thought to have been introduced by infected firewood. These so-called ambrosia beetles primarily attack already stressed bay trees by boring into the wood. Symptoms include wilted foliage discolored to shades of red or purple. The foliage eventually turns brown but remains on the branches.

Bay Tree

Bay trees (Laurus nobilis) are a ‘must have’ if you are serious about your herb garden. The fragrant leaves are used to give a rich flavour to soups, stocks, stews and more! Why not under plant your bay tree with herbs like thyme, parsley and rosemary and you’ll be making your own bouquet garni in no time 🙂

Also known as bay laurels the ancient Greeks and Romans made wreaths from the foliage and presented them to successful athletes and academics. And now you’ll be able to answer a trivia question on the origins of the expression ‘to rest on one’s laurels’.

How To Grow a Bay Tree
Bay trees are pretty versatile and will grow in full sun or part shade. They are drought, frost and salt tolerant but need to have good drainage. If planting into clay soil help break it up with eco-flo gypsum.

Bay trees can handle poor quality soils but will grow better if compost and aged manure is dug in at planting. Don’t forget to water the tree in with eco-seaweed to encourage new roots to grow as quickly as possible.

Water trees regularly and deeply until after their first summer and by then they’ll be quite drought tolerant. Trees left to their own devices can eventually get quite tall (up to 10m) but this takes many years as they are slow growing. They can be easily kept small with a prune once or twice a year (they make great topiary or hedging plants). Alternatively grow them in a pot to restrict their size.

Unfortunately bay trees are prone to sending up new shoots from their roots (called suckers). Avoid digging the soil around the tree as damage to their roots will trigger the suckers. If the suckers are left to grow they’ll create a dense shrub-like plant. If you want to keep your bay as a single trunk then they’ll need to be controlled (options listed below).

Fertilising and Harvesting Bay Trees
When trees are young fertilise every 2 weeks with eco-seaweed and eco-aminogro to encourage more growth. Established trees in the ground will be happy with a top up of compost/manure/organic fertiliser pellets one or twice a year. If you pick a lot of leaves or are growing your bay in a pot then keep using the eco-seaweed and eco-aminogro combination every 2-4 weeks.

Bay leaves can be picked any time of the year and used fresh from the tree or dried depending on the type of dish. Bay leaves are mainly used whole in cooking and removed before serving although they can be ground and added to soups, stews and stocks.

Pest and Disease Problems for Bay Trees
Bay trees are pretty tough but can still have a few problems:

  • Aphids and mites – release one of our Backyard Buddies to eat their way through the pests (Gracey for the aphids and Pete for the mites).
  • Sooty mould – this black fungus grows on a sugary substance exuded by sap sucking pests (like scale and aphids). It does take time though for the mould to flake off even when dead. Take to it with a hose or brush if it’s bothering you.
  • Bay trees can be susceptible to a few different fungal spots but it is rarely a big deal if the tree is growing in full sun and otherwise healthy. If they persist and your tree is suffering then spray the foliage every 1-2 weeks with eco-seaweed and eco-aminogro to strengthen the leaves and enhance natural resistance.
  • Suckers – It’s best to attack them when they’re small and are easier to control. Spot spray with Slasher Organic Weedkiller to effectively kill the sucker but without harming the main tree. Thoroughly spray the sucker stem for the best results. Alternatively suckers can be cut or pulled off the root or dug up. Keep an eye on the area in case the sucker reshoots.

HOW TO CARE FOR BAY TREES

BAY TREES IN CONTAINERS OR OPEN GROUND?

This article is primarily about growing bay trees in containers however they can also be grown in the open ground when given the correct conditions. The particular requirements for growing open ground bay trees are:

  • a temperature which does not drop below -5°C (32°F). Below this temperature the tree may be damaged especially if subjected to windy conditions at the same time. We have seen bay trees grown successfully in temperatures lower than this but they are in well-protected positions and generally next to the walls of heated buildings. For more detailed information about how frost affects bay trees and how to prevent it, .
  • the soil must be free-draining, heavy clay soil is not suitable. If your soil is clay then digging out a large area and mixing the soil with lots of compost and sharp sand can make the conditions OK.
  • their position should be protected from strong winds which would damage the leaves. They prefer a full sun or lightly shaded position in the UK.

If you can provide these conditions then you also need to remember that bay trees which are not regularly pruned can reach a height and width of 12m (38ft) so allow enough space when planting.

GROWING BAY TREES IN CONTAINERS

Bay trees grown in containers generally take three forms. The bush tree as seen in the picture below, (click to enlarge the picture), standard or lollipop formed, and those which have been subjected to topiary and grown into a specific shape.

Container grown trees thrive on being regularly pruned either into specific shapes or simply pruned to keep them to a required height and spread. Not only are they excellent evergreen plants but at the same time their leaves can be used for a huge number of cooking recipes.

BEST POSITION FOR BAY TREES IN CONTAINERS

The best place to position your bay tree is based on years of experience. Getting the correct position will go a long way to avoiding those dreaded brown leaves and other environmental problems. In summary:

  1. The first rule is to grow your bay tree out of harsh winds. That includes both cold winter winds and scorching summer breezes. We would go so far as to say that this rule is the most important of all.
  2. In a position where it won’t get too much water. This is especially important in spring, autumn and winter where natural UK rainfall levels will be higher than in summer. Bay trees do not like water-logged roots at all. Place the pot / container on stands if possible to allow excess water to drain away as quickly as possible.
  3. In winter, position the container either in an unheated greenhouse or outside against a heated house wall. This will prevent wind burn and provide some minimal protection against harsh cold weather. Never bring your bay tree into a heated house, it will damage it, significantly in most cases.
  4. In full sun or semi-shade? Before you decide on that make sure the 3 conditions above have been satisfied. If they have, your bay tree will grow very happily in semi-shade although they have a slight preference for full sun in normal UK weather conditions.

BUYING BAY TREES IN CONTAINERS

Buying bay trees can be something of a minefield. Pictures on the internet are often misleading as far as true size is concerned and of course, the bay tree you receive may well not be anywhere as good as the picture portrays!

It’s not unusual to pay £50 for a standard lollipop bay tree in good condition so make sure you buy from a reputable company. You may pay a couple of pounds more but you are far more likely to receive a tree which is worth the money.

Packing is also important, a badly packaged or transported bay tree can easily be damaged. Customer service is also vital if there is a problem. Choose a company which has been in business for several years at least, that in itself a guarantee. Companies which have traded for many years are still trading for a reason.

Out of all of them, our personal recommendation would go to Crocus at the current time. if you want to order a bay tree from them online.

BAY TREE CARE

When you buy a potted bush bay tree it may have been grown so that a number of shoots, growing from the main roots, form the young tree you see above ground. This provides you with an ideal opportunity to split off one or two of the shoots and replant them as separate bay trees. These individual shoots are perfect material for forming another bush or experimenting and start growing a standard bay tree – all for the cost of a single plant.

One online supplier of Bay trees supplies them grown with multiple stems, Victoriana Nursery. If you click on our link to them here you will automatically be given a 10% discount (on everything you buy from them) at the checkout summary. No codes, no fuss just a 10% discount!

To do this gently burrow into the compost around the base of a shoot and trace it down as far as you can. At that point break it from the main root with as much of the stem roots in tact as possible. Now just pot it up in multi-purpose compost to the same depth and water well. The bay stem will grow away with almost no check whatsoever.

Your new bay tree will, in all likelihood, benefit from being potted up soon after you buy it. Multi-purpose potting compost will do just fine especially if the pot has a bit of weight to it. If the pot is a light plastic then you can give it some weight by potting the new plant into John Innes Number 2 compost. Drainage is important so add some stones to the base of the pot before adding compost.

When potting up a bay tree only transfer it to a pot which slightly bigger than the previous one – 5cm / 2in wider at most. If a potted bay tree is given too much room it can often suffer for a long period of time.

For more drainage it’s a good idea to put pot feet under the base of the pot to keep it off the ground and let excess water flow away in rainy conditions. As far as feeding is concerned, a small handful of long-lasting fertiliser such as blood, fish and bone once a month (April to September) will do just fine. Sprinkle it over the surface of the soil and gently work it in to stop it blowing away.

Water sparingly only when the soil surface is definitely dry. Every three years or so re-pot your bay tree into a slightly large container. Take this chance to gently tease some of the old compost from the roots and the surface, replacing it with new compost.

WHEN AND HOW TO PRUNE BAY TREES IN CONTAINERS AND POTS

Bay trees are very tolerant of minor pruning although when they are hard-pruned they may take a year or so to recover. The best time to prune you bay tree is in late spring through to mid summer. Cut away any dead or damaged leaves to a healthy bud which is facing in the direction you want the stem to grow. Cut to shape in exactly the same way. We would suggest that a maximum height of 135cm / 4ft 6in is about the tallest most people can effectively manage for an untrained bush shaped bay tree.

Bay trees often throw up “suckers” or new shoots from just below or just above the soil level. That’s fine if you are growing them in a bush shape, they will simply expand the plant at the base which is beneficial. However, if you are growing standard bay trees with a bare stem these suckers don’t look good. They should be pruned off with a sharp pair of secateurs if growing above soil level. If growing below soil level just remove some of the soil around the base of the sucker and prune it off as low down as possible. The sucker may appear again in a few months so just do the same again. It doesn’t take many attempts (most times one will do) before the shoot stays pruned! The pruned suckers can be used to propagate new bay trees but that is outside the scope of this article.

WHEN AND HOW TO PRUNE LARGE BAY TREES

Large bay trees withstand even very hard pruning very well including cutting back the main trunk, it’s difficult to permanently damage an established one. However they are well known for taking two or three years to get back into shape.

Like many trees they are best pruned in late spring during a dry period. The plan of action, if you want to halve the size of a large bay tree without disfiguring it completely, would be to prune away about a quarter of the tree in year one then slightly less in year two and finally tidy it up to the required size in year three. Regular pruning after that annually in early spring will keep it to the size you want. It really is that simple!

Your next question may well be what can the bay tree wood and leaves be used for? Obviously some of the leaves should be dried out and given to friends and family for use as a herb. If you have kids then they will find it fun to make a bay laurel wreath either to crown their heads or hang off the door. Young, new bay tree wood can be carved and if you have any really large branches then trim them up to make a walking stick. Let the wood season and dry out before using it and you will have a walking stick for life.

PRUNING BAY TREES TO A LOLLIPOP / STANDARD SHAPE

There is very little information on the internet showing how to prune bay trees to a lollipop shape because the process takes three to four years. However we have done exactly that and the picture below shows the results of our efforts – click the picture to enlarge it.

Two things particularly surprised us when growing this bay tree, the first being how easy it was to achieve even though it took four years. The second surprise was how little support the tree required. That slim cane you see supporting the trunk has stood the test of time.

If you enlarge the picture you’ll see more clearly that maybe the top lollipop part of the bay tree isn’t as tight as shop bought ones but remember a bay lollipop tree of this height would probably cost you in excess of £60 in a garden centre. If we wanted to improve the shape we would prune the stems again to only two shoots to keep a tighter round shape at the top.

To prune a young single-stemmed bay tree to become a lollipop or standard bay tree first start by removing all the shoots from the main stem (but not the leaves) except the top main growing shoot. As the bay tree grows in height remove any shoots which appear, normally from between a leaf and the main stem.

After two to three years the stem should have grown to about 90cm / 3 foot . When the tree has reached just below the required height leave four to six of the topmost shoots which emerge from the main stem to grow. These shoots will then form the bushy top part of the lollipop tree. Prune out the tip of them main stem to stop the tree growing higher.

As the top shoots grow, prune the tips after each shoot has formed two to three side shoots. Make sure you prune down to a bud which is facing inwards to encourage a dense top of the lollipop.

Standard bay trees are liable to snapping in high winds and will need the support of a cane tied into the main stem. In the initial stages of growth, without a support, your tree will probably very soon start to list to one side and it is at this stage that a cane will be required. This is not so much to support it (when young the stems are very flexible) but more to ensure the main trunk grows upright and straight. As the tree grows more, the support will become too short and you will need to replace it with a taller cane, you may need to do this three or four times.

Tie the main trunk to the support cane at several points as it grows.

The first picture below shows a young bay tree growing slightly lop-sided. The second picture below shows the same tree tied into a bamboo cane to encourage it to grow straight upwards. Click either of the pictures to enlarge them and see more clearly.

KEEPING THE LOLLIPOP SHAPE

If you don’t prune a lollipop shaped bay tree it will tend to lose some of its shape over a few years. Two things will happen, firstly some stems will grow longer than others causing the ball shape to become uneven. Secondly the ball shape will become less tight and the stems will spread out rather loosely. There’s nothing wrong with this, however some people do prefer to maintain the tight shape as it was when they bought the plant.

To help do this prune the stems two or three times a year using a pair of secateurs. Prune them to the length you want to maintain the shape. You will find that there are not many stems to prune if you do it regularly but it will encourage other stems to form which will make the shape more dense.

When you prune a stem always do it to an inward facing bud even if that means pruning it slightly too short. When the bud just below the cut starts to grow it will then grow inwards rather than outwards which also helps maintain the tight lollipop shape.

RECOMMENDED VARIETIES OF BAY TREES

There are very few varieties of bay tree aside from the normal one found at garden centres, Laurus nobilis. The other alternative is to go for the cultivar Laurus nobilis Aurea which has yellower leaves.

PESTS AND DISEASES OF BAY TREES

BAY TREE SUCKER

The first signs you will notice are the edges of some leaves curling inwards and start to thicken. The edges turn yellow then brown.

For more signs of Bay Tree Sucker and how to treat them, .

BLACK POWDER COATING ON LEAVES

This often looks like a fine layer of soot and can affect all the leaves or just a few. It is caused by sap-sucking insects such as aphids which excrete a sugary liquid. This liquid attracts moulds and that is what causes the leaves to appear to be coated in black.

Firstly, wash away the black coating with water. If that doesn’t remove it, add a couple of drops of washing up liquid to the water and wash off with that. You will need to wash each leaf individually with a cloth. This will not only make the leaves look and photosynthesise better but it will avoid the unwanted attraction of other insects such as wasps, bees who feed off the sugary liquid.

Then you need to treat the insects which are causing the problem. Simply washing the leaves individually will remove aphids, pay particular attention to the undersides of the leaves. If that doesn’t work then a trip to the garden centre for a general purpose insecticide may be required.

BROWN OR YELLOW LEAVES

The most commonly heard complaint is why bay tree leaves are turning yellow or brown and dyeing off. The first step in remedying this problem is to rule out the bay tree sucker as the cause of the damage. If it’s bay tree sucker then the new and younger leaves will be curling inwards, older leaves will be mainly unaffected. When you uncurl a damaged leaf you will likely see a tiny woolly insect possibly with some white fluffy cobweb stuff around or near it. If this is the case, see the previous paragraph.

If not, the cause of the brown leaves is almost certainly environmental – too much or too little water possibly, damage from cold and wind or occasionally too much heat. The key to coping with this damage is to get the conditions correct for your bay tree. Follow the steps below and then wait and see what happens over the next six months, chances are that your tree will recover:

  1. Over-watering, this can be caused by hand watering, badly positioned containers or just too much rain.
    ACTION
    If the container is in a tray then remove it from the tray and put it on pot legs or at least a brick or two to ensure it never stands in water and allows maximum drainage. Only water the plant when the top part of the soil is dry. To check, burrow a finger gently in the soil to a depth of about 3cm / 1in, if the soil feels at all damp at the base of your finger then don’t water any more until it feels dry.
  2. Under-watering, in winter, spring and autumn (in the UK) this is rarely a problem as long as container grown bay trees are open to the elements. Natural rainfall is usually sufficient.
    ACTION
    In warm weather, summer in particular, a container grown bay tree needs regular watering to keep the soil moist but not water-logged.
  3. Cold and wind, either of these can cause significant browning and yellowing of leaves, if both conditions are present then you will certainly have problems. The problem may not be apparent for a couple of months so you need to protect your bay tree from these conditions throughout the year.
    ACTION
    Bay trees may well be damaged when the temperature drops below -5°C (32°F), so in winter position them near the walls of a heated house out of the way of strong winds. Often the best place in winter is in a corner between a fence on one side and the walls of the house on the other. They should be moved to a more open position in summer. Clear the area around the container of all vegetation and preferably place it on a layer of gravel. For more detailed information about how frost affects bay trees and how to prevent it, .
  4. General care, dead leaves, compacted soil and lack of feeding can all contribute to the general health of your bay tree. If you decide that browning leaves are a problem then take the following action as well.
    ACTION
    Remove the top 3cm / 1in of compost and replace it with clean, new compost.
    In spring and summer, if you haven’t fed your bay tree for a few months, scatter some long-lasting fertiliser (blood, fish and bone but not a nitrogen rich fertiliser) onto the soil surface and gently work it into the surface. Only do this if you have forgotten to feed your plant previously and only a very small handful – a level tablespoon should be enough at first.
    Remove all leaves which are completely brown or yellow and dispose of them well away from the plant (preferably burn them).
    Over the next few months inspect your plant weekly (we are guilty of an almost daily look at our bay trees) and remove any damaged leaves. Be careful not to remove all the leaves at once because even partly damaged leaves contribute to the growth of a plant, but remove a few at a time. Damaged leaves attract bugs and disease and slowly removing them will improve the overall health of your bay tree.

WHITE MARKS ON BARK AND STEMS

See the picture below. This is the Wooly Scale insect and we have a section here devoted to this problem.

BARK IS PEELING OFF / CRACKING

This is an environmental problem rather than a pest or disease. With bay trees in containers the problem is caused mainly by overwatering and / or allowing the soil to dry out and then overwatering. Too much water is causing the trunk to swell and split the bark.

The solution is to restrict the amount of watering and also try and maintain an even level of moisture in the soil. Bay trees in containers are very tolerant of lack of water for a month or so. If this has occurred don’t soak the soil with water, water it back to a moist condition over a month or so.

Bad drainage can also be a problem causing water to accumulate in the container. Raise the container slightly off the ground on gravel or pot legs.

Splitting / peeling and cracking bark can also be caused by prolonged periods of very cold weather. The frost gets into small existing cracks and opens them up.

There is nothing which can be done once the bark is split but if the upper part of the tree has healthy leaves on it the tree will, in all probability, be fine if drainage is increased. In cold weather move containerised trees to a protected position against the side of a house or into an unheated greenhouse.

BAY TREE LEAVES HAVE HOLES IN THEM

There are two main causes of holes in the leaves and they can easily be differentiated. There is also a third, less common cause, which is the leaf cutter bee. If the damage is to the edges of the leaves it is most likely caused by vine weevils. The damage looks like a bug has munched on the edges of the leaves leaving semi-circular, ragged damage. The picture below illustrates the damage.

Typical Vine Weevil leaf damage

Vine weevils can cause significant damage to all bay trees (the leaf damage is just the start) especially those in containers. Take action immediately as described in our page on how to identify and treat this pest.

The other common cause of holes in bay tree leaves is called Shot hole which is a fungal infection. the picture below shows the typical hole damage to the leaves which are not normally around the edge.

Shot hole damage to leaves

The damage first appears as brown circular marks on the leaves. The brown spots fall out leaving holes.

The copper fungicide Bordeaux Mixture has previously been recommended as a spray to prevent fungal diseases in bay trees. However it has now (or soon will be) withdrawn from sale in the UK. Currently there are no alternatives which have been scientifically proven to be anywhere near as effective as Bordeaux Mixture

Various alternatives are suggested, for example aspirin solution or milk, but none have been proven to have any effect.

The fungus can also be controlled simply by reducing the number of affected leaves and buds. Firstly, remove all fallen leaves and twigs from around the base of the tree. If the area is water logged, try to provide good drainage to reduce humidity. Prune off affected twigs which have infected buds.

Bay tree leaves can occasionally be damaged by leaf cutter bees although they tend to go for other plants first. The damage they do is similar to the vine weevil picture further above this article. But leaf cutter bees are tidy and neat bugs and the holes at the edges of the leaves are very rounded and not ragged.

Also, you should see the bees at work if they are affecting your bay tree. Our advice is to do nothing, the damage is normally minor and they are unlikely to return to the same site next year. If you spray chemicals to kill these bees the spray will also kill other valuable garden insects.

COOKING AND BAY LEAVES

Bay leaves are normally sold in shops and supermarkets in their dried form and they retain most of their flavour for about six months. To retain this flavour store them in an airtight container kept in a cool, dark place.

Freshly picked bay leaves have a slightly stronger flavour and if you have grown them yourself you know exactly what chemicals and preservatives have been used in their cultivation – hopefully none. The flavour and aroma, dried or fresh, provides a background to many soup, meat and sauces recipes. In Europe the main source is from Turkey and they come from the true bay leaf tree Laurus nobilis. In some other parts of the world they use what is known as the Californian bay tree but this is in fact not a bay leaf tree, it is Umbellularia californica.

To dry bay leaves, cut a couple of stems from your plant and hang them by cotton in a warm dry place. They will have dried out after two to three weeks and can then be put in an airtight jar or plastic bag for use whenever required.

DO BAY TREES HAVE FLOWERS?

We are asked this question frequently and the simple answer is yes. The picture below proves it beyond doubt!

In our experience flowers are produced in April / May time but only on mature specimens. Younger bay trees do not produce flowers. The flowers are very small, about the size of a five pence piece. We don’t remove them because they are unlikely to affect the growth of a mature bay tree.

Flowers on a standard Bay Tree
Click to enlarge picture

Another question we are asked is are there male and female forms of bay trees and if so how do they differ? The answer is that yes, there are male and female forms. The difference becomes apparent in autumn. Female forms will produce berries (and they contain seeds) whereas male forms of bay trees do not generally produce berries.

BAY TREE LEAVES AND WOOD CHIPS AS A MULCH?

Bay tree leaves and the wood is generally regarded as being acidic, they also take a long time to compost down well. For these reasons we would use them sparingly on a compost heap or as a mulch. In small doses they are fine but not as a main ingredient for compost or mulch.

Sometimes our readers ask specific questions which are not covered in the main article above. Our
Bay Tree comment / question and answer page
lists their comments, questions and answers. At the end of that page there is also a form for you to submit any new question or comment you have.

BACK TO MAIN HERB PAGE

Diseases Of Bay Trees : How To Treat A Sick Bay Tree

You don’t have to be a cook to be familiar with bay laurel. This common seasoning is an often seen member of home landscapes. It is an easy-to-grow plant but is susceptible to a few bay tree diseases. Many of the most prevalent pathogens create problems on the foliage, the part used in cooking. Preventing these diseases of bay trees can help protect both the plant and your secret recipe ingredient.

Staving Off Bay Tree Diseases

Bay trees are remarkably adaptable in USDA zones 8 to 10. This perennial is really more of a large bush than a tree, but it accommodates shearing into almost any form. Bay laurel has a fairly rapid growth rate at 12 to 24 inches (30 to 61 cm.) per year. It is a low maintenance plant with few requirements or problems. In the event of any issues in this stoic plant, it’s important to learn how to treat a sick bay tree and what the most common diseases are that occur in this plant.

The plant’s foliage has several uses. Leaves are resistant to fire, may be dried and used to repel moths, or included in recipes for a unique flavor and aroma. In ancient Greek times,

the plant was made into a crown, leaves sweetened rooms and bedding, and acted as an astringent and salve. The plant makes an excellent no-fuss ornamental with its glossy, green leaves.

It is the roots that are the primary target of bay tree diseases, although pest problems favor the leaves too. Insects, like scale and psyllids, can cause distress in the tree that look like disease symptoms. Plants are susceptible to Phytophthora root rot and some cultural and soil based problems.

Cultural Diseases of Bay

Many of the symptoms you notice on a bay that seem to be disease are actually mineral or nutrient based. Nitrogen deficiency causes yellowing in leaves, which is easy to cure by adding an organic mulch around the root zone.

For diseases of bay tree that occur due to lack of minerals you will have to perform a soil test. This will tell you if you need to add peat moss to reduce soil pH and make manganese more available to the plant. Or, in the case of certain minerals such as iron and zinc, this will tell you if a foliar spray containing that mineral is useful.

Beware of excess minerals which cause such symptoms as chlorosis and leaf tip dieback. Avoid fertilizing bay laurel excessively, as woody stemmed plants do not generally need annual feeding. Instead, focus on making soil healthy and using organic amendments.

How to Treat a Sick Bay Tree

When the problems aren’t cultural or soil based, it is probably a pathogen. Phytophthora is the most common in bay plants. It is considered both a root and crown rot. The disease stems from a fungus that lives in soil and proliferates in wet conditions.

Symptoms range from dry, stressed leaves to dark, streaky bark. If the disease progresses, a gummy sap emerges. Increased drainage around the root zone can help prevent the disease. If the plant is affected, treat with fungicide. A foliar spray works well. In extreme cases, dig the soil away from the roots of the plant and replace with uninfected soil. Container plants should also have the soil replaced.

Other diseases do not seem to affect bay trees much. Check the plant carefully before diagnosing the problem and encourage good organic care to enhance the bay laurel’s health.

Bay Laurel Tree Diseases

Lorbeerblätter image by Teamarbeit from Fotolia.com

Bay laurel trees are used in a variety of herbal remedies precisely because they are simply not subject to very many diseases. These remedies take advantage of this tree’s hardiness and attempt to use it to your health’s advantage. Even if you do not personally prefer to eat or drink your bay laurel leaves, you may still enjoy its long, evergreen foliage. However, if you are not aware of the signs and symptoms of the few bay laurel tree diseases out there, you may find that you have a suffering or dying bay laurel tree on your hands before you have a chance to save it.

Bay Anthracnose

Bay anthracnose is a fungal infection that attacks the bay laurel tree from the inside but manifests itself first in the leaves. First the tips of the leaves will turn dark brown or black, followed by the remainder of the leaves. The tip will begin to gray as the rest of the leaf dies. Left unchecked, an anthracnose infection can lead to leaf loss and defoliation as well as the death of twigs and branches as the fungal infection breaks the tree down. To control the infection, use sterile pruning to remove affected leaves and branches, then monitor the tree for further signs of trouble. You can also treat the tree with a fungicide and limit watering to early morning hours, and only when the soil is dry. If the tree continues to suffer, you may need to remove it to prevent infection of other trees.

Phytophthora Ramorum

Phytophthora ramorum is a fungal infection like anthracnose, and many of the symptoms of these two diseases are similar. This infection also starts out with black leaf tips, and as the leaves die they may become outlined in yellow before they turn brown, black and then gray. However, P. ramorum can also start out as black spots in the middle area of the leaf that blotch until they destroy the leaf from the inside out. As the leaves, fall you may notice trouble with the branches as well. As with anthracnose, remove affected limbs and foliage using sterile pruning techniques and treat the tree with a fungicide if necessary. As yet, there are no reported cases of bay laurel tree death due to P. ramorum.

Bay Sucker

The bay sucker is also known as the jumping plant louse. These tiny insects infect bay trees and live in nooks and crannies in the bark during the winter. Then, they create thick, yellow lesions on the leaves, which cause the leaves to yellow and curl around the edges. Bay suckers can be eradicated by washing the undersides of bay leaves with a weak soap solution or by removing affected leaves and branches. While bay suckers will not kill your bay laurel tree on their own, they can lead to a variety of problematic secondary infections that can hurt or kill your bay laurel.

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