Heucheras are amazing plants, but unfortunately, sometimes they get in trouble. You will learn about one of such problems in this article.
To treat heuchera rust, remove all diseased leaves and destroy them. Spray it with an aqueous solution of fungicide. Do not overwater Coral Bells because a moist environment is beneficial for rust.
I will describe this disease and how to deal with it in more detail in the following sections. Also be sure to read the article Coral Bells Care – Planting, Growing & Cultural Information.
What caused the rust?
Puccinia heucherae is the cause of leaf rust on heuchera leaves. This pathogen parasitizes only Heuchera. Accordingly, other perennials in the garden are not affected.
What is interesting is that Heucherella is very rarely affected by this disease, because it is a hybrid of Heuchera and Tiarella. The latter never get rust. Also, Saxifraga can become a target of this pathogen.
Rainy and cloudy weather provides ideal conditions for the germination of the spores of this fungus. In dry weather, it is less active. So frequent watering and constantly moist soil are the most common causes of heuchera rust.
It usually occurs in warm weather from spring through summer into fall. Young leaves are the most susceptible. But all other parts can also be affected.
The first symptom is dark spots on the underside of the leaf. At first, the diseased leaf is almost indistinguishable from the healthy leaf.
Over time, the spots become increasingly browner and more pronounced. Young leaves may become deformed or have indentations on top of them.
The spots will then develop into pustules from which new spores will emerge and the cycle will repeat. The spores will settle on the new leaves and germinate.
Heavily infested leaves can turn completely brown and shrivel up. In this case, pustules may not have time to mature and new spores will die.
In addition to the leaves, leaf petioles can also become infested. A large number of spots can cause them to drop to the ground.
The first thing to do if rust has affected your heucheras is to remove all diseased leaves. Do this carefully to avoid damaging the stem or spreading a minimum of spores to new leaves.
Next, destroy the leaves completely, preferably by burning them. Do not leave them to rot in your yard or make compost out of them. Also, don’t throw them in the trash to avoid spreading the disease even more throughout the neighborhood.
Spray the bush with an aqueous fungicide solution. There are many rust fungicides available, but it is best to choose ones that contain one of these chemicals:
Copper sulfate also works well against rust. Copper ions can kill almost any fungal pathogen.
Repeat the spraying after 1 to 2 weeks. It will be good if you use several fungicides alternating them. This is because the fungus can develop resistance to one product if it is used without alternatives and on a regular basis.
The last thing you can do is to replace the topsoil. Carefully remove 1 inch topsoil of the old soil around your heuchera and put the same amount of fresh sterile soil in its place.
Always check plants before you buy them. Carefully inspect all leaves for spots or anything unusual. Also, check the quality of the substrate and the root system.
Do not plant the heuchera immediately, but put it aside for a few weeks. Very often the fungal diseases do not show up in the nurseries but when you take the plant home they will start to develop.
Clean up any plant debris around the bush. Rotting plant parts are a perfect medium for disease to develop.
Do not overwater, not only to avoid root rot but also to prevent rust. A wet environment encourages fungal growth. So if you let the soil dry out 2 inches between waterings, you will avoid most diseases.
Provide good air movement around the shrubs. Don’t plant too densely, with at least 6 inches of space between plants.
Will the plant recover?
Heuchera is able to recover from rust even if it loses most of its leaves. If you do as recommended above, in most cases the plant will get well and begin to grow new leaves.
This recovery process can take about a month or more, depending on the damage caused by the disease. To help the plant, water it when the soil is about 2 inches dry. If it is growing in poorly drained soil, repot it in more drained soil.
Water it 2-3 times with a multi-purpose liquid fertilizer at 2-week intervals. This will give it a little boost for recovery.
If heuchera is growing in full sun, shade it for a few weeks. The shade will help it grow new leaves faster and evaporate less water.
Read more: Why Are My Coral Bells Turning Brown?