General gardening topics

Pieris Problems – pests, diseases and other problems

Last updated on March 14th, 2022

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Pieris are compact, slow-growing shrubs that delight gardeners from all over with their pink/red young leaves that take on cream colours during adolescence and end with green. The white, bell-like flowers add a certain Lily of the Valley look which is why the plant is commonly called the Lily of the Valley shrub. 

Adding year-round interest to your garden it can be devastating when there are suddenly pests, diseases or other problems getting in the way. Thankfully, there are things you can be on the lookout for and prevent against. 

Pests

Pieris Lacebug

The one pest with which you must contend is the Pieris Lacebug. This is a winged insect and you will know when it has invaded your plant because your leaves will become pale and bleach in appearance, which is something that is often mistaken for a nutrient deficiency. You can typically find the lace bugs on the underside of the leaves.

For those who live in Southern England, this can be a particular problem because it was first discovered in a garden in Windsor in 1998 and is now widespread.  There are some varieties that are more resistant than others, something you can investigate beforehand.

If you notice damage from the lace bugs, you can use a regular bug spray killer as long as your plant is not currently in flower, usually, they make an appearance in the early summer, which is when it should be sprayed although it may also need another treatment later in the summer. If you apply the bug killer whilst your plant is flowering it will also cause harm to any pollinating insects. If the infestation is not too bad you can live with it or prune out the affected growth after flowering.


Diseases

Leaf Spot

Fungal leaf spot is the first problem you will likely face in terms of diseases. The way you can decide whether your plant is suffering from this disease is by examining the leaves. This disease causes brown spots to appear on the leaves, which get incrementally larger until such time they take over the entirety of the leaf, causing them to fall off. Fungal leaf spot requires warm humid conditions so one of the ways to prevent it from taking place is to keep the foliage on your plant dry and encourage air circulation.

When you water do so early in the morning and at the base of the plant. This will help your plants absorb the water and dry out early. Moreover, you should remove any weeds and make sure the plant is not overcrowded. This can be the situation reconciled by some light pruning to prevent overcrowding and improve air circulation. If you mulch your plants in the spring you want to keep the mulch about 30cm minimum away from the base of the plant so that it doesn’t rot.

Leaf Spot Treatments

If your plant is suffering from a fungal leaf spot you can treat it with a fungicide. You can also mix a natural treatment that is comprised of baking soda and water, 1/2 teaspoon of baking soda for every 4 litres of water.

Phytophthora Root Rot

On rare occasions, your plant may be susceptible to phytophthora root rot. If your plant has this it will turn yellow, maybe even purple, something that happens to one branch early on and then spreads to the rest of them. This is a fatal disease. To prevent that you want to make sure your plant is never waterlogged or left in any type of standing water, and this you can ensure with proper drainage and allowing the plant to dry out between watering. 


Other Problems

Lack of Nutrients

There are other problems you might face. If the leaves have turned a sickly yellow shade it could be caused by a lack of nutrients. This type of plant loves acidic soil so you might need to apply a fertiliser base for acid-loving plants, specifically something for Azaleas or Rhododendrons. You can check the pH levels of your soil and if you find that the soil in which your plants are grown is far too alkaline and there’s no way to change that level regularly you might have to move it. However, this needs to be done around October when the plant is dormant for the winter. Consider planting in a container with ericaceous compost if your soil isn’t acidic.

Too Much Sunlight

Another cause of sickly yellow leaves could be sunlight. These plants are native to mountainous areas and they need dappled shade or even full shade, so if they are positioned in direct, strong sunlight all day it could cause the leaves to turn yellow.

Pieris not Flowering

If your plant has never flowered, this is another problem that indicates it is simply not growing properly. Similarly to the sickly yellow leaves, you should check the soil levels to make sure the soil is properly acidic. If your soil is alkaline you will need to plant it somewhere else, most people with this problem end up planting in a pot complete with ericaceous compost.

If your plant is already being grown in a container it could have become rootbound. If you lift up the container in which it is planted and you see the roots are sticking out through the drainage holes it is rootbound, and it will need a larger container with fresh compost or regular feeding at a minimum.

As long as you don’t have a very young plant that can take a few years to flower, you should be able to reconcile the issue of lack of growth and subsequent lack of flowering by checking these two things.

By making sure you keep an eye out for signs of pests, and vigilantly treat diseases, your Pieris shrub can continue living a healthy life with brightly coloured leaves and white flower clusters.

Last update on 2022-03-17 / Affiliate links / Images from Amazon Product Advertising API

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4 Comments

  1. Can the roots of the Pieris be trimmed
    As I don’t have a bigger pot????

  2. John Moore

    Hi Mollie, I would say yes, just don’t remove too much, the roots still have to support the size of the plant. With some plants like roses I’d say just chop as much as you need off but with Pieris just be a little more causous.

  3. Janet White

    Hi have two forest flames in large pots I’ve had for years with no problems but the last two years when the pink shoots are coming through and looking really healthy then after a week or so they start dry and shrivel, I feed them Ericaceous food.

  4. John Moore

    Hi Janet, perhaps an early frost has caused this? Also, could they have gotten dry, perhaps their root-bound and could do with potting up into a new pot. If you moved them to a new position two years ago perhaps its also in a position where it not as protected from frost as it was in previous years. Hope this helps

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