SQUASH – COURGETTE – ZUCCHINI

Other vegetables

Courgette is the French name, Zucchini the Italian. Zucchini is the plural so if you’re only cooking one, it’s actually a zucchino. Courgettes belong to the pumpkin or squash species in the gourd family. This long green or yellow vegetable ranges in size from 10 to 30 centimeters. Any longer and they’re better to boast about than they are to eat.

The taste is neutral and the flesh is firm, which makes courgettes a useful ingredient. But they do need a little cooking to make them really interesting. Deep fried or stuffed oven-baked courgette flowers are a delicacy around the Mediterranean.

Choosing courgettes

Courgettes should be smooth and springy, almost like a cucumber.

Avoid really big ones as they can be woody with a nondescript flavor.

Decorative, often multicoloured, squash and zucchinis are not meant for human consumption as they may contain a plant poison.

Storing courgettes

Courgettes are quite tough and can last at least a week in a cool place after harvesting.

Preparing courgettes

If you’re cooking large amounts, cut them up in advance and store them in the fridge in a plastic bag.

How to cook courgettes

You can eat courgettes raw, e.g. thinly sliced or finely shredded in a salad. But the mild flavor emerges much better if you cook it.

Grate for courgette fritters, fry, grill, oven bake, braise, boil or deep fry.

Fried courgettes are a fixture on the meze tables of the Mediterranean. Pour plenty of olive oil into a pan and fry thin slices or thick sticks, depending on the final texture you’re aiming for.

Make veggie fritters: Grate the courgette, salt it and leave to stand for an hour. Squeeze out the liquid and mix the grated courgette feta cheese/halloumi, pepper, dill/mint, flour and egg. Mix together and fry the fritters until golden brown in olive oil.

Grilled courgette! Cut it lengthwise or diagonally into slices to give you a flat surface to decorate with grilled stripes. Place on the grill. If you want your vegetables to have more flavor, take the warm courgette and marinate it after cooking in a balsamic vinaigrette.

Oven bake courgette with other vegetables on a large baking sheet. Drizzle with oil, sprinkle with sea salt and place in the oven at 190°C for 30-40 minutes.

A quick dinner: Cook pasta. Fry courgette. Roast pine nuts. Grate parmesan. Mix pesto and the courgette into the pasta and sprinkle with parmesan and roasted pine nuts.

Boiled courgette has a soft but consistent texture of its own and adds a mild flavor to casseroles and stews, such as ratatouille.

Deep fried courgette – and courgette flowers – are a delicacy. Read about deep frying here.

Braising courgette to bring out the flavors: Cut into pieces all the same size and brown in butter and/or oil. Add a little liquid – for example water, stock, wine, beer – and reduce until the courgette is done. It should retain its texture and chewiness.

The classic

Ratatouille, French vegetable stew with courgette, aubergine, tomato, onion, pepper, thyme and garlic. Apart from the rat aspect, the film Ratatouille gives an excellent picture of life in a professional kitchen. Watch it!

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Cucumber, Squash, Melon & Other Cucurbit Diseases

Prevention & Treatment: This fungus can survive in the soil for many years. Planting resistant varieties (Table 1) is critical in preventing this disease. Careful water management is also important in minimizing root stress. There are no chemical treatments available for control.

Viruses

Cucumber mosaic virus (CMV) on squash.
Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, www.insectimages.org

There are several common viruses that can affect cucurbits, including Cucumber mosaic virus (CMV) and Watermelon mosaic virus (WMV). Infected plants may be stunted or have leaves that are mottled, crinkled, or a light green color. Fruits may be irregular in shape, mottled or warty. Various insects transmit these viruses.

Prevention & Treatment: There are no chemicals available to kill viruses. Chemical control of the insects that spread the viruses may minimize the disease. This control method is difficult, because infection occurs immediately after an insect feeds, and insects migrate freely between plants. A good control strategy is to maintain healthy and vigorous plants, plant recommended varieties and monitor your garden for any unusual symptoms as they occur. Keep the area clear of weeds that can harbor insects. Choosing separate areas for early and late plantings may help to reduce virus severity in the late plantings.

Blossom-End Rot

Blossom-end rot appears as a dark-colored dry rot on the end of the fruit where the flower was. The problem is caused by a lack of calcium in the developing fruit. It is an indication that calcium is lacking in the soil or that the plant does not have the ability to take up enough calcium. When growth is rapid, not enough calcium may be delivered to the blossom end of the developing fruit.

Blossom end rot on watermelon.
Clemson University – USDA Cooperative Extension Slide Series, Bugwood.org

Prevention & Treatment: Help prevent blossom-end rot by having your soil tested through your local county Extension office before planting, and lime according to recommendations, usually to pH 6.5. Always maintain an adequate supply of moisture, especially during fruit growth. Mulch plants to prevent rapid drying of the soil and water plants during extended dry periods. Apply 1 to 2 pounds of gypsum per 100 square feet as a supplement to liming on calcium deficient soil. Lime and/or gypsum should be applied before planting.

Do not over-fertilize plants with excessive nitrogen or potassium. Excess amounts of these nutrients reduce the uptake of calcium in the plant. When plants are dark green, extra fertilizer should not be applied.

Irrigate with 1 inch of irrigation water per week if there is inadequate rainfall. Cultivation near crops should be shallow to avoid root injury. Removing fruit with symptoms is recommended.

Table 1. Some Disease-Resistant Varieties for South Carolina.

Cantaloupe
Ambrosia Resistant to some powdery mildews
Mission Tolerant to downy and powdery mildew
Cordele Resistant to some powdery mildews and Fusarium wilt
Earlidew Resistant to Fusarium wilt
Cucumber, slicing
Ashley Resistant to some powdery mildews and downy mildew
Burpless Resistant to some powdery mildews
Poinsett8 76 Resistant to downy mildew, powdery mildew, angular leaf spot, anthracnose and scab
Supersett Resistant to downy mildew
Dasher II Resistant to powdery mildew, angular leaf spot, anthracnose, scab and cucumber mosaic virus
Cucumber, pickling
Regal Resistant to downy mildew, powdery mildew, angular leaf spot, anthracnose, scab and cucumber mosaic virus
Squash, summer
Multipik This yellow-fruited variety does not show greening of fruit caused by viruses (CMV, WMV)
Watermelon
Charleston Gray
Crimson Sweet
Jubilee II
Starbrite
Tiger Baby
All of these varieties have some resistance to anthracnose and Fusarium wilt.

Table 2. Preventative Fungicide Treatments for Cucurbit Diseases.

Vegetable Disease Fungicide
Cantaloupe Downy mildew chlorothalonil or mancozeb1 or copper fungicide4
Powdery mildew sulfur2 or chlorothalonil or horticultural oil + baking soda3
Gummy stem blight chlorothalonil or mancozeb1
Alternaria leaf spot chlorothalonil or mancozeb1
Anthracnose chlorothalonil or mancozeb1
Bacterial wilt no chemical control
Cucumber Anthracnose chlorothalonil or mancozeb1
Downy mildew chlorothalonil or mancozeb1 or copper fungicide4
Powdery mildew sulfur2 or chlorothalonil or horticultural oil + baking soda3
Gummy stem blight chlorothalonil or mancozeb1
Alternaria leaf spot chlorothalonil or mancozeb1 or copper fungicide4
Scab mancozeb1 or chlorothalonil
Cercospora leaf spot chlorothalonil or mancozeb1
Squash Anthracnose chlorothalonil or mancozeb1 or copper fungicide4
Downy mildew chlorothalonil or mancozeb1 or copper fungicide4
Powdery mildew sulfur2 or chlorothalonil or horticultural oil + baking soda3
Gummy stem blight chlorothalonil
Watermelon Bacterial leaf spots or fruit blotch mancozeb1 plus copper fungicide4
Anthracnose mancozeb1 or chlorothalonil5
Gummy stem blight
& black rot (of fruit)
mancozeb1 or chlorothalonil5
Cercospora leaf spot mancozeb1 or chlorothalonil5
Powdery mildew sulfur2 or chlorothalonil5 or mancozeb1
Downy mildew mancozeb1 or copper fungicide4
All Vegetables Postharvest rots Sodium hypochlorite (5.25% commercial bleach). Mix 1 teaspoon of bleach in 1 gallon of water. Dip fruit into solution and rinse. Replenish bleach periodically as needed.
1 Wait 5 days after spraying before harvest.
2 Do not apply sulfur when temperatures are above 85 °F. Sulfur should be used on muskmelons very carefully because some varieties will be damaged by this chemical.
3 3 tablespoons of horticultural oil in a gallon of water and add 3 tablespoons of baking soda. Never apply an oil spray within 2 weeks of a sulfur spray, and do not apply oils when temperatures are above 90 °F or to drought-stressed plants.
4 Fixed copper does not control downy mildew nearly as well as the other fungicides listed. Caution is advised, as copper can be phytotoxic to cucurbits, if applied at temperatures above 90 °F.
5Spray at first appearance and then at 7-14 day intervals. Avoid late-season application after plants have reached full maturity and fruit have begun to size, or cover the watermelon fruit to prevent contact with fungicide, or use mancozeb. Do not mix chlorothalonil with a copper fungicide in the sprayer.

Table 3. Examples of Fungicides Labeled for use in Home Vegetable Gardens on Cucurbits.

Fungicide Examples of Brands & Products
Chlorothalonil Ortho MAX Garden Disease Control (29.6%)
GardenTech Daconil Fungicide Concentrate (29.6%)
Bonide Fungonil Concentrate (29.6%); & RTU1
Hi-Yield Vegetable, Flower, Fruit & Ornamental Fungicide (12.5%)
Southern Ag Liquid Ornamental & Vegetable Fungicide (12.5%)
Tiger Brand Daconil (12.5%)
Ferti-lome Broad Spectrum Landscape & Garden Fungicide (12.5%); & RTU1
Copper fungicides Bonide Copper Fungicide Spray or Dust (wettable powder with copper sulfate)
Southern Ag Liquid Copper Fungicide Concentrate
Monterey Liqui-Cop Copper Fungicide Garden Spray Concentrate; & RTS2
Bonide Liquid Copper Concentrate (a copper soap)
Camelot O Fungicide/ Bactericide Concentrate (a copper soap)
Natural Guard Copper Soap Liquid Fungicide Conc.; & RTU1
Bonide Liquid Copper Fungicide RTU1 (a copper soap)
Horticultural oil Bonide All Seasons Spray Oil Concentrate; & RTU1
Ferti-lome Horticultural Oil Spray Concentrate; & RTS2
Monterey Horticultural Oil Concentrate; & RTS2
Southern Ag Parafine Horticultural Oil
Summit Year Round Spray Oil Concentrate
Mancozeb Bonide Mancozeb Flowable with Zinc
Southern Ag Dithane M-45 Concentrate
Sulfur Bonide Sulfur Plant Fungicide (dust or spray)
Ferti-lome Dusting Sulfur (also wettable for spray)
Hi-Yield Wettable Dusting Sulfur
Safer Brand Garden Fungicide Concentrate
Southern Ag Wettable or Dusting Sulfur
1 RTU=Ready to Use (a small pre-mixed spray bottle)
2 RTS=Ready to Spray (a hose-end spray bottle)

Zucchini growing problems: 10 common issues and how to overcome them

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Zucchini and other soft-skinned summer squashes are usually pretty easy to grow. But, gardeners do sometimes face struggles with these productive crops. Perhaps your vines stopped producing in mid summer? Or the fruits were small or deformed? Or maybe your plants simply died before producing any fruits? If you found yourself asking why zucchini growing problems struck your garden, this solution guide is for you.

Top 10 zucchini growing problems

Here are ten reasons why you may have faced zucchini growing problems in the past, and tips for making sure these issues don’t happen again.

Zucchini problem 1: Improper variety selection.

Not all zucchini varieties perform the same. Some are more productive than others, and some are more disease- and pest-resistant. First and foremost, when selecting zucchini varieties for your garden, be sure to seek out disease and pest resistance whenever possible. Varieties with a high level of natural resistance often perform better and produce longer. ‘Tigress’, ‘Green Machine’, ‘Burpee Golden Glory’, and ‘Yellow Fin’ are great choices.

Limiting zucchini growing problems starts with selecting the right varieties.

Zucchini problem 2: Squash vine borers.

One of the biggest zucchini growing problems is a pest known as the squash vine borer. Adult vine borers are day-flying moths that are black and red with dark wings. They’re fast flyers, so gardeners don’t often spot them. The damage caused by their larvae, however, is difficult to miss. Squash vine borer larvae feed inside the main stem of the plant, hollowing it out and eventually causing plant death. You’ll see crumbly, sawdust-like waste collected below a small hole at the base of the plant. To prevent squash vine borers, protect the lower portion of the stem with a wrap of aluminum foil (more on this technique here), or cover the plants with floating row cover until they come into bloom to keep the female moths away from egg-laying sites.

Adult squash vine borers are day-flying moths that look like large wasps.

Zucchini problem 3: Poor pollination.

Zucchini and other squash are insect pollinated, meaning a bee, beetle, or other pollinator is needed to move the pollen from a separate male flower over to a female flower. If there aren’t enough pollinators present, puny or deformed fruits are the result. If your zucchini are mal-formed and stubby on the blossom end, poor pollination is the most pressing of your zucchini growing problems. To improve pollination rates, plant lots of flowering herbs and annuals in and around your zucchini patch. You can also hand-pollinate the vines by using a paintbrush or your fingertip to transfer pollen from the male flowers to the females (more on how to hand pollinate here). Another option is to plant a parthenocarpic variety that doesn’t require pollination to set fruit, such as ‘Easypick Gold’, ‘Partenon’, or ‘Cavili’.

Zucchinis rely on insect pollinators to move the pollen from male to female flowers.

Zucchini problem 4: Powdery mildew.

Powdery mildew is among the most pervasive fungal diseases when it comes to vine crops like zucchini. This pathogen makes the leaves appear to be covered in a talcum powder-like coating. Though it’s primarily an aesthetic issue, severe cases can lead to reduced photosynthesis and reduced production. To overcome powdery mildew, space plants properly – give each one plenty of room so air can circulate and dry off wet foliage. Plant only resistant varieties, such as ‘Anton’, ‘Dunja’, ‘Astia’, and ‘Emerald Delight’, to help combat powdery mildew which is one of the most tenacious zucchini growing problems. Organic fungicides based on potassium bicarbonate (such as GreenCure and BiCarb) are effective as preventatives, as are those based on Bacillus subtilis (such as Serenade).

Powdery mildew is a difficult fungal disease that often strikes zucchini plants.

Zucchini problem 5: Squash bugs.

When it comes to insects that attack squash, none are more difficult to control than squash bugs. These shield-shaped, brown insects suck out plant juices with their needle-like mouthpart, causing stippling, yellowing, and browning of the leaves.

Squash bugs are first seen as clusters of bronze, football-shaped eggs followed by gray nymphs that feed in groups.

The best way to manage squash bugs is to head to the garden every day and inspect the top and bottom of your zucchini leaves for clusters of bronze-colored, football-shaped eggs. Squash bugs are resistant to most pesticides, but very young nymphs can be controlled with applications of insecticidal soap or horticultural oil. Our Guide to Vegetable Garden Pests has more info on this troublesome insect.

Watch this video to see a cool trick for getting rid of squash bugs organically – using duct tape!

Zucchini problem 6: Poor soil.

Zucchini doesn’t require excessively nutrient-rich soil, but it does perform best in soils that are high in organic matter with a soil pH around 6.5. If your pH is too far off that target mark, the plants may fail to produce quality fruit because the soil pH affects the availability of many different nutrients (more on soil pH here). You can also prevent many zucchini growing problems related to the soil by limiting the amount of nitrogen you add to your garden. Excessive nitrogen produces a lot of green leaves, often at the expense of good fruit production. Use only balanced, organic fertilizers on your zucchini patch and test your soil every few years to ensure it’s healthy and well-balanced.

Give zucchini plants plenty of room to grow and make sure they’re planted in soil that’s rich in organic matter.

Zucchini problem 7: Lack of water.

Zucchini growing problems can also stem from irregular soil moisture levels. If plants are allowed to dry out between waterings, fruit production can be negatively impacted. Drought stress is never good for vegetable crops, and zucchinis require consistent, even soil moisture throughout the growing season. If Mother Nature doesn’t supply your garden with at least one inch of water per week, it’s your job to add supplemental irrigation to prevent any possible issues. A 2-3 inch thick layer of mulch helps stabilize soil moisture levels and can reduce the need to irrigate during the hot summer months. You’ll find more information on proper mulching techniques here.

Mulch zucchini well to keep the soil evenly moist. This zucchini patch is mulched with newspaper topped with shredded leaves.

Zucchini problem 8: Blossom end rot.

Zucchini can also be affected by blossom end rot, just like tomatoes and peppers. This physiological disorder causes the blossom end of the fruit to rot into a dark, sunken canker. It’s caused by a calcium deficiency, but it’s the result of inconsistent watering. Calcium can only come into a plant as it absorbs water in through its roots. When there’s no water in the soil to absorb, the plant can’t access calcium either and blossom end rot is the result. To prevent blossom end rot from striking your zucchini, make sure the plants receive ample, consistent applications of water throughout the growing season. Adding more calcium will not solve the problem.

Zucchini problem 9: Bacterial wilt.

Though this pathogen tends to be more problematic on cucumbers, it sometimes strikes zucchini as well. Sadly, this is one of those zucchini growing problems that’s the kiss-of-death when it strikes. Spread by the cucumber beetle, bacterial wilt causes otherwise healthy plants to wilt and die without prior warning. To combat potential problems, keep cucumber beetles in check by trapping them on yellow sticky cards fastened to stakes just above the tops of the plants.

Growing healthy, productive zucchini happens when you provide plants with everything they need.

Zucchini problem 10: Not enough sun.

Though it isn’t the worst of the zucchini growing problems you might face, lack of sun can definitely affect plant health and production. Zucchini plants need a minimum of six to eight hours of full sun per day. Lower light levels can result in long, lanky plants with pale green foliage and reduced yields. Poor pollination can also be a side effect of light levels that are too low because pollinators tend to prefer foraging in sunnier areas, particularly on cooler days. Select a full-sun site when planting your zucchinis.

Zucchini plants require six to eight hours of full sun per day to perform their best.

Zucchini growing problems don’t have to decimate your crop

Though zucchini growing problems may strike your garden from time to time, with these management tips, you can manage the issues organically and enjoy bushels of delicious zucchini all season long.

For more on growing healthy zucchini, check out these related posts:

Cucumber plant problems
Guide to Vegetable Garden Pests
A Handy Guide to Harvesting Vegetables
Types of Landscape Mulch
A Compost Guide

What challenges have you faced with your zucchini crops and how did you overcome them?

We suspect a few of our growers out there may struggle with blossom end rot this season due to the dry weather that we’ve had lately. Once the fruit is affected, there’s no going back, but you can prevent other fruits from the same plant from being affected.

Blossom end rot is recognisable by the very end of the squash or courgette turning brown/black and rotting as it grows. They basically get a soggy bottom. Mary Berry wouldn’t be impressed. It happens when the plant is short of calcium, but realistically they will be short of calcium because there is not enough water in the soil for them to draw the calcium up though the roots. (It’s unlikely that your soil will actually be deficient in calcium).

In this dry weather we’ve had lately, it’s easy to let the soil dry out – your plants may look fine on the outside, so it’s difficult to spot when they need more water (yellowing leaves are a quick sign that your plants need more water) which is what makes us suspect that quite a few of our Rocketeers will see blossom end rot in their squashes and courgettes this year.

The good news is that blossom end rot is not a contagious disease so if one courgette on a plant gets it, then it doesn’t mean that the other ones will. Just try to keep your plants well watered so that the soil is consistently moist and the new fruits should be ok. Good luck!

Garden Myths – Learn the truth about gardening

Blossom End Rot (BER) is a disfiguration found in fruiting vegetables, like tomatoes. It also affects peppers, watermelons, egg plants and apples. This problem is usually blamed on a shortage of calcium, but this turns out to be a myth.

Blossom end rot in tomatoes

Blossom End Rot – What is it?

Blossom End Rot or BER shows up as a small wet water-soaked spot at the blossom end of the fruit. Over time it darkens to a brown or black color and becomes leathery and hard. This is not a disease, as reported by many web sites, nor is it the result of insect damage. As the fruit grows, something goes wrong with the normal growth process and the cells in the fruit start to die. The dead cells turn black and hard. It is a physiological condition due to the plants environment.

BER is most common on the first fruits of the season, but it can occur at any time.

The fruit, once affected, will not develop properly, and can be discarded so the plant can focus it’s energy on newer fruit.

Blossom End Rot – What Causes it?

For years it was claimed that a lack of calcium was causing Blossom End Rot since fruit with BER had low calcium levels.

More recently, scientists have had a closer look. It turns out that the problem is one of moving calcium around inside the plant, not necessarily a shortage. Various ‘transporter’ compounds, such as gibberellins and a recently isolated protein are responsible for moving calcium to points in the plant where it is needed. Calcium is required for cell growth and so it is required in fairly large amounts by the developing fruit. When these transporter compounds are not doing their job properly, it results in low levels of calcium at specific points in the plant.

In the case of Blossom End Rot, the transporter compounds are just not moving enough calcium to the growing fruit.

You might be thinking to yourself that BER is a calcium deficiency, but that is not correct. The rest of the plant can have lots of calcium and BER can still develop. Compare this to a serious earthquake. The thing the affected people need most urgently is drinking water–they have a shortage. We don’t have a global shortage of drinking water–we just don’t have it in the right place at the right time.

Once you understand the real problem, it becomes obvious why many of the remedies for BER don’t work.

How do You Solve Blossom End Rot?

In many cases the plant seems to grow out of the problem over time. As mentioned above, the first fruit of the season is most likely to have the problem, and after that, fruit grows normally–for no clear reason.

The following are some solutions that have been proposed:

1) Fertilize with calcium. It is possible that the soil is deficient of calcium, and if this is the case fertilizing with calcium will help eliminate BER. However, most soil has lots of calcium and if it does have calcium, fertilizing with more will not help the problem. Too much fertilizer may exacerbate the problem by making it harder for the plant to absorb calcium. For example, excess ammonium from of nitrogen can make it harder for the plant to absorb calcium.

2) Spray calcium fertilizer on the leaves ie foliar feed. First of all, foliar feeding is not a good long term solution for feeding plants especially for home gardeners, at best it is a quick fix solution. Calcium in the leaves does not move away from the leaves because it only “moves in the plant via the xylem and moves with the transpirational water flow from the roots, up the plant and into growing points” (quoted from Dr. Linda Chalker-Scott). Calcium has no ability to flow from the leaves via the phloem to the developing fruit.

An interesting experiment measured the effects of calcium foliar spray on tomato plants and found that it affected both plant growth and reduced BER (ref 6). It is possible that the increase of calcium in the leaves results in more calcium being directed to the fruit from the roots. This is just one study, but calcium foliar spray may reduce BER.

3) Spray calcium on the fruit. Fruit has a tough waxy outer skin that is not very permeable, and it has no stomata to allow nutrients to enter. It is even less likely to absorb calcium than the leaves. This does not work.

4) Treat the plant with Epsom salts. I don’t know why people keep recommending Epsom salts to solve problems–it’s just silly. Epsom salts is magnesium sulfate–it does not contain calcium! Blossom End Rot has nothing to do with a magnesium shortage.

5) Water more, or less. There is some evidence that water levels in the plant play a role in calcium levels in various parts of the plant, and water levels may have an effect on the transporter compounds. The problem with this advice is that it is difficult to know if you need to increase or decrease water levels. Keep the soil moist and don’t over water.

6) Grow a different variety of tomato. This can work. Some varieties are more likely to get Blossom End Rot so growing a different variety could solve the problem for you.

7) Adding bonemeal or lime to the soil. Both these products contain calcium and if your soil is deficient of calcium, these might help. Keep in mind most soils are not deficient of calcium, so I would not use these products until you have a soil test done.

8) Don’t over fertilize with nitrogen. This is important and can contribute to BER. Too much nitrogen causes the plant to grow more leaves. As water is drawn towards the leaves, it carries calcium with it which may in turn reduce the amount of calcium going to the fruit. Over fertilization also increases the amount of salts around the roots, which makes it harder for the plant to absorb calcium.

There is no magic bullet to solve Blossom End Rot. Treat plants the way they want to be treated (good soil, compost, regular water etc) and you should not have serious problem. But if you do have BER, don’t believe everything you read.

1) Blossom End Rot by RHS: http://rhs.org.uk/advice/profile?pid=395

2) Why Calcium Deficiency is Not the Cause of Blossom End Rot in Tomato and Pepper Fruit: http://www.sciencedirect.com/science/article/pii/S0304423814002830

3) de Freitas, Sergio Tonetto; Mitcham, Elizabeth Jeanne; Jiang, Cai-Zhong. 2012. Mechanisms Involved in Calcium Deficiency Development in Tomato Fruit in Response to Gibberellins. Journal of plant growth regulation, v. 31, no. 2, p. 221-234

5) Blossom End Rot – Transport Protein Identified: http://phys.org/news/2011-11-blossom-protein.html

6) Effect of Foliar Application on Tomato Growth: http://www.bepls.com/feb_2014/7.pdf

7) Photo Source: NC State University

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The fruit on my zucchini squash begin to grow, but quickly turn brown and rot. Why

The rotting of the small squash fruits could be due to poor pollination or blossom-end rot.

For squash fruit to develop fully, bees and other pollinators must transport pollen from the male flowers to the female flowers. If the female flowers aren’t pollinated properly, the fruit will begin to grow and then suddenly shrivel up and die. Bees and other pollinators are less active in rainy weather. Rainy weather could be responsible for poor pollination and rotting of the small fruits. Drier weather conditions should increase pollinator activity.

Blossom-end rot is a physiological disorder that occurs on tomatoes, peppers, eggplant, and summer squash. On zucchini and other summer squash, the blossom end of the fruit begins to rot and within a short time the entire fruit has rotted. Blossom-end rot is caused by a lack of calcium in the developing fruit. In most cases, there is no need to apply calcium to the soil. Try to maintain an even moisture supply by watering once a week during dry weather. Also, do not over-fertilize plants. Uneven moisture supplies and excessive nitrogen inhibit calcium uptake.

Zucchini Plants Flowering But Not Producing Fruit

There are a number of reasons your zucchini plants may not be producing much fruit. To start, it’s important to understand that zucchini and other squash plants are monoecious, meaning they produce separate male and female flowers on the same plant. While these flowers may look very similar at first glance, there are some distinct differences once you take a closer look. The most obvious differences are the small immature fruits at the bases of female flowers and the long thin stems of male flowers (pictured above). Early in the growing season, squash plants tend to produce more male than female flowers. While you may have tons of flowers, in order to produce fruit you must have both male and female flowers at the same time.

Bees and other pollinators are usually responsible for transferring pollen from the male flowers to the female flowers, which ultimately leads to fruit development. If there are few bees in your garden, you’ll likely have poor pollination and fruit set. Bees are sometimes few and far between in urban areas. If you think this is the case in your own garden, you can try playing the role of a bee yourself by hand pollinating the flowers. The pollen of squash plants is very sticky and is formed in the center of the male flowers. You can try using a small paint brush to move some of the pollen from the male flower to the stigma of the female flower. If that sounds too tedious, you can also just remove the male flower and gently roll its pollen onto the stigma of the female flower. It’s best to try hand-pollination early in the morning as squash flowers open early and only last for one day. Also keep in mind that squashes can only be fertilized by their same species. A zucchini cannot be pollinated by a winter squash and vice versa.

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Zucchini

Zucchini is an ideal plant for the beginner vegetable gardener because it is quick and easy to grow. Zucchini or courgette (Cucurbita pepo) is closely related to cucumber, watermelon, pumpkin and squash. There are also many ways to use the prolific fruit.

Planting schedule

Warm: April – September except for arid areas where September is the best.
Temperate: September – January
Cool: October – January

In temperate and cool areas it is best to sow seeds in small pots (try making them out of newspaper) indoors or in a greenhouse since they do not like cold weather. They usually germinate in 1 – 2 weeks and can be planted when there are several true leaves. In warm areas, direct sow seeds.

Position

Find a sunny spot with at least 6 hours of sun per day. It is best that they are sheltered from wind since their large leaves can catch the wind and cause damage to their soft stems. In exposed locations a trellis or some other form of support will be needed.

Because zucchini plants are large and sprawling, leave about 50 – 60 cm between them. You might sow seeds or plant seedlings closer and then thin them out to the desired spacing.

Talking Dirty

Like most fruit and vegetables, zucchini like good well-draining soil – raised beds will provide appropriate drainage or plant on a slight mound of soil.

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Add plenty of compost or aged manure a week or so before planting and then again when flowering starts.

What about the water?

Since the fruit are very fleshy, zucchini need plenty of water – irrigation 2 – 3 times per week or a thorough deep hand watering once per week. It is important to avoid watering the leaves, especially late in the season when mildew and other diseases can be a problem. Don’t worry if the leaves wilt on very hot days – they will recover as long as the roots zone is watered regularly. Mulching with pea or lucerne straw will help keep soil moist.

Are we there yet?

Zucchini have separate male and female flowers and, like most species, it is the females that product fruit. The male flower grows directly on the stem of the plant in the leaf axils (where leaf meets stem) on a long stalk, and they are slightly smaller than the female. The male flower grows directly on the stem of the plant in the leaf axils (where leaf meets stem) on a long stalk, and they are slightly smaller than the female. Inside the flower, females have a rounded stigma whereas the male has a long stamen with pollen on the outside.

This is important to recognize if you find that flowers are forming but they bloom and fade, with no fruit growing afterwards. It could be that your garden lacks pollinators especially in recent years when bee numbers have been declining. If this occurs, you could try hand pollination. Use a fine paint brush in the mornings and carefully brush it against the male stamen and transfer pollen to the female stigma.

Planting other flowering plants, especially nasturtiums, which are a good companion plant for zucchini, will help attract bees to your garden.

Fruit usually appear 5 – 8 weeks after planting. Zucchini need to be regularly harvested to encourage continuous cropping. They are usually harvested quite small and immature as allowing them to continue growing results in fruit that is too big to be used as a vegetable. So watch carefully since once they start appearing since they can grow rapidly producing large unwieldy fruit. It is best to harvest when they are around 12 – 20 cm long.

The flowers are also edible – this is a good way to use the occasional excesses of male flower. They can be used in salads, as garnish, and even fried or stuffed with cheese, bacon, mushroom or tomato and baked.

Pests and the rest

Few pests cause serious problems for zucchini but, like all Cucurbits, they can be susceptible to a range of fungal diseases. In particular, powdery mildew, but this is easily eradicated. Another potential problem is blossom end rot, which isn’t a contagious disease, but is caused by calcium deficiency.

Varieties

Zucchini are available in a range of shapes and colours, not just the familiar dark green sausage-shape that is readily available in supermarkets, but yellow, striped in different shades of green and even curved or almost round. For example, ‘Blackjack’ is a prolific bush variety with very dark-green long fruit, and ‘Golden’, is a yellow-skinned variety. A number of seed suppliers stock a variety of heirloom varieties that are worth investigating, including ‘Crookneck Early Summer’, which is very suited to those who aren’t able to harvest fruit as frequently, as they remain an edible size for much longer than other varieties. There are also more compact varieties, such as Cocozelle, which means you don’t need to provide support or have a large garden space.

Information sources:

Yates Garden Guide, 42nd Edition, 2006, published by Harper Collins Publishers.
Blazey, C., The Australian Vegetable Garden – what’s new is old, 2001, published by New Holland Publishers.
Wikipedia

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