Learn About Heuchera
Common Disease Problems
Botrytis: This fungus causes a grey mold on flowers, leaves, stems and buds. It thrives in cool wet weather conditions. Burpee Recommends: Remove affected plant parts, avoid watering at night and getting water on the plant when watering. Make sure plants have good air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Cercospora Leaf Blight: Small flecks which develop a yellowish halo appear on the leaves and turn brown and coalesce. They cause the leaves to wither and die. Burpee Recommends: Remove infected plants and destroy all plant debris.
Downy Mildew: This fungus causes whitish gray patches on the undersides and eventually both sides of the leaves. Burpee Recommends: Avoid overhead watering. Provide adequate air circulation, do not overcrowd plants. Do not work around plants when they are wet.
Heuchera Rust: This fungus first appears on older leaves and may be mistaken for naturally dying leaves. It forms the characteristic rust colored pustules on the undersides of the leaves. The spores form within the leaf and cannot be wiped off. The upper leaf surface has pock mocking. This rust is host specific and should not spread to other types of plants. Burpee Recommends: Remove affected plant parts as soon as possible and destroy them. Be careful not to remove the growing points.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps which feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Rabbits: Rabbits may eat mostly the flowers of heuchera. Burpee Recommends: Use a hot pepper wax spray or rabbit repellent.
Slugs: These pests leave large holes in the foliage or eat leaves entirely. They leave a slime trail, feed at night and are mostly a problem in damp weather. Burpee Recommends: Hand pick, at night if possible. You can try attracting the slugs to traps either using cornmeal or beer. For a beer trap, dig a hole in the ground and place a large cup or bowl into the hole; use something that has steep sides so that the slugs can’t crawl back out when they’re finished. Fill the bowl about ¾ of the way full with beer, and let it sit overnight. In the morning, the bowl should be full of drowned slugs that can be dumped out for the birds to eat. For a cornmeal trap, put a tablespoon or two of cornmeal in a jar and put it on its side near the plants. Slugs are attracted to the scent but they cannot digest it and it will kill them. You can also try placing a barrier around your plants of diatomaceous earth or even coffee grounds. They cannot crawl over these.
Sunburn: Heuchera may become sunburnt if exposed to direct sunlight during the heat of the day. Burpee Recommends: Be sure to site your plants so that they are protected from afternoon sun.
Vine Weevil: This insect cuts irregular notches in leaf margins and grubs feed on plant roots, sometimes causing the death of the plant. Adults are approximately 5/16 inch long, dull black with dirty yellow marking on the wing cases. The grubs are c-shaped, 3/8 inches long, with light brown heads. Burpee Recommends: Handpick adults at night, shake the plants over newspaper to dislodge them. Check under pots where they hide during the day. Check with your Cooperative Extension Service for pesticide recommendations.
Article by David Marks
Heuchera Rust is a relatively new problem in the UK, first identified in 2004. It has quickly become far more common over the last decade. It is a strain of fungal rust which affects only heucheras and is properly called Puccinia hucherae. To date, it has not been known to affect any other plants.
SYMPTOMS OF HEUCHERA RUST
The symptoms of Heuchera Rust are:
- Initially small sunken or raised areas on the upper surface of leaves. The areas are normally brown
- The underside of leaves will have raised, rust coloured spots on them
- The raised spots may well also appear on the stems and upper sides of the leaves
- Badly affected leaves will be distorted, the raised areas may fall out leaving small holes in the leaves
- Older leaves are more affected compared to new growth
Heuchera Rust on upper and lower leaf surfaces
LIFE CYCLE OF HEUCHERA RUST
Two factors make Heuchera Rust relatively easy to control. The first is that it cannot affect other plants and neither can rust on other plants affect Heucheras. The second is that, in common with other types of rust, it needs live plant material live.
Understanding the life cycle of a pest or disease is key to working out how to defeat it. The life cycle of Heuchera Rust is described below.
MID SPRING TO EARLY SUMMER
When temperatures begin to rise in mid spring to early summer rust spores are released from infected living plants which land on other plants and infect them. The ideal temperature range for spore release and germination is 10°C to 20°C / 50°F to 68°C although it will still occur outside of these ranges. Spores are transferred by wind and rain drops.
EARLY SUMMER TO LATE AUTUMN
When the spores land on a suitable plant they germinate. Rust fungus then infects the new plant and begins to feed on it. The time between the spores infecting a plant and the visible signs of the infection appearing can be as short as a week but as long as a month. It all depends on the temperature and humidity levels.
It’s important to realise that infected plants may not always show immediate signs of infection. The infection easily spreads form one part of the plant to another (and to nearby plants) over the summer and autumn.
In winter, as the temperature falls, the infection rate slows down, the fungus effectively overwinters on infected living plants.
PREVENTING HEUCHERA RUST
Several steps can be taken to minimise the risk of your plants suffering from Heuchera Rust. These are set out below:
- Remove any leaves or stems which are dying or in bad condition. Older leaves are more prone to Heuchera Rust
- Clear up all decaying matter around your plants. Well rotted organic matter as a mulch is fine however because it contains only dead plant material which cannot support the growth of rust
- Don’t crowd your plants. This reduces airflow which in turn increase the risks of rust – rust thrives in cool conditions with restricted airflow
- Rust prefers lush foliage and this is encouraged by the application of nitrogen rich fertilisers so do not use on heucheras, they do not need them
HOW TO TREAT HEUCHERA RUST
If the infection is minor we would suggest removing all leaves which are affected and then spraying with a fungicide such as Bayer Fungus Fighter Plus or Scotts Fungus Clear Ultra.
The other more certain alternative is to remove all leaves, infected or not, making sure not to remove the growing point. It’s safest to remove the leaves one by one. This will leave your heuchera looking very bare for a few weeks but almost certainly it will recover and produce new leaves.
Heucheras are very resilient plants and will easily pull through the treatment recommended above. Half measures are rarely effective in the long term so pluck up the courage to obtain the best result. Make sure you either burn the leaves or put them in the domestic rubbish bin (not a compost bin).
One of the hottest-selling plants at the garden center is a perennial named coral bells, beloved in summer for its wands of delicate flowers and year-round for its gorgeous foliage.
Its vibrant beauty makes the gardener want to dote on it. This is where things go awry.
I bought three and planted them in a spot I thought would do them well: Their tops in dappled shade, their feet in rich, moist soil. A few weeks later, they died, then vanished. The only evidence of their existence was the credit card bill.
If there was a perverse silver lining to this disappointment, it was in learning from other gardeners that their plants too proved to be stinkers.
This doesn’t stop the supply of them, or the amazing number of new varieties that are available or in the pipeline. Coral bells arrive at the garden center at their peak and their allure is understandable.
In summer, the plant sends up slender spikes bearing blooms in shades of white, red or pink. But it is the foliage that really catches the eye: Arranged in neat mounds, the leaves are mottled and veined in striking combinations.
However, there is no single coral bells, which botanists call heuchera. Demand is so great for the plant in all its glory that breeders have introduced almost 200 varieties with leaf colors variously described as purple, ruby, bronze and amber. Green varieties abound too, also with eye-catching variegated patterns.
The key to success with coral bells is to be picky in the varieties you select, even if that means turning your back on some real beauties, and being careful in how you grow them.
Coral bells are native to arid regions or dry woodland, hybridizer Martha Oliver said, and mulching and clay soil promotes rapid rot. Traditionally they have been used in rock gardens where the plant crowns remain drained and dry.
“They grow best in a gritty, sandy soil,” her husband, Charles Oliver, said. The couple owns the Primrose Path Nursery in Scottdale, Pa., specializing in heucheras. “I just think people are siting them wrong and they tend to put mulch around the crown,” he said.
I have three varieties of `Harmonic Convergence,’ a cultivar raised by the Olivers. These will be planted in a freer draining site than before, needless to say.
An evaluation of coral bells by the Chicago Botanic Garden in Glencoe points to some of the perennial’s problems in garden beds. The botanic garden’s staff planted 64 varieties for a long-term study. Even with professional care, 21 of them — one in four — didn’t make it past two seasons.
Of those that remained for the five-year test period, several had unwanted traits: leaves that flattened to reveal an open crown; poor to fair flower coverage; flower stems too thin to hold the blossom clusters upright; and a tendency to lift out of the ground, either through elongation of the crown or frost heaving.
But the biggest problem was the tendency of some varieties to rot away. Coral bells have shallow roots that need moisture, but too much moisture, especially during winter dormancy, induces stem and crown rot diseases.
All in the family
When buying coral bells, you may want to ask for its family tree. Most varieties are hybrids of three species, Heuchera americana, H. micrantha and H. sanguinea.
Many of those that rotted in the Chicago study are derived from the last species, which is native to New Mexico and Arizona and needs excellent drainage.
Among those that died early were `Carmen,’ `Chocolate Veil,’ `Frosty’ and `Pewter Moon.’ Of those that survived the first two years, several later declined or died from stem rot.
Hawke rated the best as `Bressingham Bronze,’ `Cappuccino,’ `Molly Bush,’ `Montrose Ruby,’ `Palace Purple’ and `White Cloud.’ “Each of these coral bells received the highest marks based on good habit, healthy foliage, high flower production and winter hardiness,” he wrote. Of these, the highest scorer was `Molly Bush,’ which has purple foliage and white blooms, but is not as attractively variegated as some of the choicest varieties.
He noted that his report already is outdated because so many new varieties are introduced each year, “but many of the top-rated older cultivars are still available.”
It also may help shape a new view of coral bells and its limitations and uses. Ironically, the plant may join epimediums, hellebores and euphorbias as being a useful perennial for one of the most difficult landscape areas, dry shade. Its need for drainage also makes it a good candidate for container gardens, if you can avoid overwatering it.
The Chicago Botanic Garden report, in color newsletter form and titled “Plant Evaluation Notes, An Evaluation Study of Coral Bells,” is available. Send a $3 check payable to the Chicago Botanic Garden to Hawke at: Plant Evaluation Notes, Chicago Botanic Garden, 1000 Lake Cook Rd., Glencoe, IL 60022. The garden’s Web site is www.chicagobotanic.org.
<br> Penny O’Callaghan is a new gardener horrified to experience the devastation caused by vine weevils. A fan of coloured-leafed heucheras, she was upset to find her treasured potted ‘Marmalade’ severed at its base. On close inspection she found the compost “crawling with tiny white caterpillar-type bugs”. A dark-leafed heuchera has gone the same way. Is this a pest specific to heucheras – and what should she do?
Although they feed and breed in dry, sheltered garden soil (particularly around low evergreens such as euonymus), vine weevils seem to do most damage when they home in on container-grown plants with fine roots (especially heucheras, primulas and violas), which they regard as ideal places to deposit their eggs. On hatching, grubs feast on roots.
Adults are black, slow moving, largely nocturnal beetles about 5mm long. Distinctive small notches in the margins of leaves and flowers act as their calling cards. Control is achieved via drenching the soil to destroy grubs – either with a biological control based on nematodes (Vine Weevil Killer from Nemasys), or chemical control with Bayer Garden’s Provado Vine Weevil Killer. Robins love picking through grub-infested compost spread out on a sheet – after which it is best binned
Connecticut State The Connecticut Agricultural Experiment Station
Plant Health Problems
See Perennials for a detailed discussion of problems that may occur and are common to most herbaceous ornamentals.
Diseases caused by Fungi:
Downy mildew, Plasmopora spp.
Downy mildews typically cause leaf spots with downy white or gray patches under the leaves. The downy growth results from the production of spores called sporangia which are wind-dispersed between plants. Disease is usually favored by cool wet weather.
Control may include cultural means of reducing humidity and leaf wetness. Control may also be achieved with the use of fungicides applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut is mancozeb. Consult the label for dosage rates, safety precautions, and directions for use.
Gray mold, flower and leaf blight, Botrytis cinerea.
This fungus occurs everywhere and commonly infects senescing or damaged plant parts such as old flowers, causing a fuzzy gray mold. Spores are produced which are easily blown around. From these tissues the fungus moves into healthy stems and leaves, causing a damaging blight. Disease is favored by cool wet conditions and the presence of overripe fruit or old flower petals.
Sanitation is the most important means of control. Remove dead flowers before gray mold develops. If disease has moved into leaf or stem parts, control may also be achieved with the use of fungicides applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut is thiophanate-methyl. Consult the label for dosage rates and safety precautions.
Leaf spots, Cercospora, Colletotrichum, Phyllosticta or Septoria spp.
Leaf spots are very common, typically sharply delimited necrotic areas on plant leaves caused by a wide variety of pathogenic species. Leaf spots usually are favored by wet conditions and may become important if a large number of lesions are present or if they start to coalesce.
Under those conditions, control may also be achieved with the use of fungicides applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut are thiophanate-methyl and sulfur. Consult the label for dosage rates and safety precautions.
Powdery mildew, Erysiphe or Sphaerotheca spp.
Powdery mildews are obligate plant parasites which grow vegetatively on the plant leaf surface, sending haustoria, structures which absorb food from the host, into epidermal cells. The white mildew seen on the leaf is a combination of vegetative mycelium and spores borne in chains on upright conidiophores. Wind-dispersed mildew spores can germinate without free water under high humidity conditions, and disease is often severe when conditions are humid but dry. Small black over-wintering structures called perithecia are often found in powdery mildew affected areas.
Control may also be achieved with the use of fungicides applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut are potassium bicarbonate, ultra fine oil, sulfur, triadimefon, or thiophanate-methyl fungicides. Consult the label for dosage rates, safety precautions, and directions for use.
Rust, Coleosporium or Puccinia spp.
The term rust refers to both the disease and pathogen causing the disease. Rust fungi are specialized obligate parasites which can cause disease on one (monoecious) or two (heteroecious) host species. Symptoms of rust infection include rust-colored spores or gelatinous horns in powdery pustules on leaves or stems. Surrounding tissue is discolored and yellowed, and plants are often stunted.
Control of heteroecious rusts may be aided by removal of the alternate host, but for most perennials, control may also be achieved with the use of fungicides applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut are sulfur and mancozeb. Consult the label for dosage rates, safety precautions, and directions for use.
Wilts, Verticillium spp.
These pathogens infect the vascular or water-conducting tissues of plants, and cause wilt symptoms by impairing water flow. As a result, symptomatic plants may flag or wilt on one side of the plant, leaves may be twisted and yellow on one side, turn brown and hang down prior to drying up. Overall, the plant exhibits drought symptoms despite adequate soil moisture. If the stem is cut open near the base, the vascular tissues are typically brown or discolored.
Wilt control involves removal of infected plants and associated roots and soil. The pathogens survive in soil and plant debris for long times, so disposal of plants and soil without spread is important.
Black vine weevil, Otiorhynchus sulcatus.
The larvae of this weevil often injure ornamental plants by feeding on the roots. The grubs devour the small roots and tunnel inside the crown of coral bells, weakening the plants. Leaf notching by adults can also be unsightly. The 1/2″ long adult weevil is black, with a beaded appearance to the thorax and scattered spots of yellow hairs on the wing covers. Only females are known, and the adults are flightless. They feed nocturnally, notching the margins of the foliage. The legless grub is white with a brown head and is curved like grubs of other weevils. Adults and large larvae overwinter, emerging from May – July. The adults have to feed for 3-4 weeks before being able to lay eggs. Treating the soil with insect pathogenic nematodes may control the larvae, and should be the first line of defense against this pest in landscape plantings. Acephate and fluvalinate are among the compounds registered for control of this pest in Connecticut, and should be applied when there is adults feeding and before they start laying eggs. The usual timing for these foliar sprays is during May, June and July at three week intervals. Insecticide resistance is very common; be aware that adults may appear to be dead following contact with fluvalinate, but may recover from poisoning within a few days. Consult the label for dosage rates and safety precautions..
For other insect pests, See Perennials.
Heucheras are remarkably pest and disease free but there is one disease has recently appeared that can be a bit of a problem. Heuchera rust is easily overlooked, it tends to appear on the older leaves and might be mistaken for tatty leaves that have done a whole year and are getting rather tired…..but once you turn a leaf over you’ll see the tell-tale pustules and they are hard to confuse with any other Heuchera affliction.
Rust tends to be worse in damp humid airless conditions – ie weeks of rain and damp air
Dry sunny condtions help to dry out the spores that cause it
Some varieties never seem to get Rust at all –
Heucheras have their own special type of rust called Puccinia heucherae, it won’t spread to other plants in your garden.
The image below is of both surfaces of leaves from a plant of H ‘Lime Rickey’ it’s a yellow foliage type. The upper surface (left) shows the distinctive pock marks and the lower surface shows the little pockets of spores which eventually burst and scatter themselves on the wind.
Because the spores develop within the leaf tissue the spore clusters can’t be picked off like a gall or scale insect. Take a look with a hand lens and you’ll see the transparent covering of the outer layer of leaf tissue.
It’s worth trying to keep rust under control because it spoils the appearance of the leaves and weakens the plant.
The first thing to do is cut off the leaves of the affected plant, all of them but don’t remove the growing points of the plant. Heucheras grow back very quickly and when it comes the new foliage should be fresh, rust free and lovely. Dispose of the leaves so as to avoid spreading the spores – burning is a good idea or pop them in the rubbish bin (not with the green waste).
You can spray with Systhane (Roseclear) or Fungus Fighter to prevent further development of the disease. Always follow the instructions on the product label.
Check plants before you buy them
Cut off old leaves in the early Spring to make sure air circulates well amongst the new ones and to remove possible infection.
You can spray against rust, begin in Spring when the weather starts to warm up and repeat as directed on the packet.
Don’t compost infected material
Consider planting other types of plants among your Heucheras so that they act as a bit of a barrier
If you have to water your Heucheras do it in the morning so the plants are dry before dark – rust likes humid over-night conditions – dry Heucheras are less likely to be attacked.
Simple plant hygiene is important – clean secateurs to avoid transferring spores and wash your hands after dealing with an infected plant.
Simple precautions and awareness of the disease should help to keep your gorgeous Heucheras healthy, enjoy them.
Heucheras and Tiarellas
Heucheras and tiarellas are small, evergreen, perennial plants that are simply a delight in any garden. Grown mainly for their neat little bundle of decorative leaves heucheras and tiarellas are great for borders, rockeries or mass planted under trees and shrubs. They’re also well suited to pots and can even be grown as an indoor plant.
Heucheras and tiarellas are sometimes called coral bells and are native to North America where there are more than 65 species that feature an incredible array of leaf colours, patterns and shapes. The main difference between the two is that tiarellas have more heartshaped leaves which are predominantly green with coloured markings, while heucheras have leaves that are ruffled and more colourful. The flowers also differ slightly as tiarellas are more star shaped and are usually on taller stems. Hybrids between the two are common and are known a heucherellas.
Regardless of the type they are all easy to grow and are hardy, adaptable plants. You’ll find they will grow in hot, humid situations as well as cool climates and are so beautiful you’ll be hooked in no time!
How To Grow Heucheras and Tiarellas
Heucheras and tiarellas are frost hardy and can grow in a range of positions from full sun to part or full shade. Check the label of the plant you’ve purchased as it will vary from plant to plant. However you can’t go wrong with planting any of them in either dappled shade under trees and shrubs or in a spot which gets morning sun and afternoon shade. Any that are planted in all day sun will need to be kept moist during hot, dry periods. In shadier positions they will handle a little bit of drying out once established.
They will grow in most soil types but perform best in rich, free-draining soils so add plenty of organic matter before planting eg compost and bulky aged manures. The added organic matter will also help with moisture retention and keep them happier for longer. In clay soils add eco-flo gypsum to help improve drainage.
Plant your plant and water in with eco-seaweed to help it establish faster. Apply an organic mulch around the soil to suppress weeds and maintain moisture.
If growing indoors then pot them up into a slightly larger sized pot using a premium quality potting mix. Water in with eco-seaweed and position in a bright spot.
Maintenance and Fertilising Heucheras and Tiarellas
Every 2-3 weeks mix eco-seaweed and eco-aminogro together and apply either over the foliage or direct to the soil. Deadhead spent flowers (this will encourage extra flowering) and pull off any dead or tatty leaves. Each spring top up the compost and mulch around the base of the plant and add some pelleted organic fertiliser. Pretty simple really.
Plants can be divided every 2-3 years in autumn or late winter if they become congested. This will be more noticeable with an indoor potted plant than those growing in a garden bed.
Pests and Diseases of Heucheras and Tiarellas
Heucheras are tough little guys that aren’t bothered by many pests and diseases. Mealybugs may attack plants but can be treated with a couple of thorough sprays of eco-oil or eco-neem.
Powdery mildew – to reduce repeat infections increase air circulation around the plant and avoid wetting leaves when watering. Regular applications of eco-seaweed and eco-aminogro will also build strong healthy plants with more disease resistance.