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Buxus (box) plants are hardy specimens. Reviving them depends on what the problem is and what causes in the problem in the first place. Here are some of the most common problems and what to do about them. In addition, I discuss pruning that helps revive your buxus, no matter what’s wrong with it.
Waterlogging and root rot
Waterlogging of a plant usually occurs when you over-water it. Alternatively, you may be watering the plant just the right amount but the excess water isn’t draining away. It’s remaining around the bottom of the plant and soaking into the roots.
In both of these cases – and this applies to buxus plants that are in the ground or planted in containers – the roots become saturated with water. This prevents them from taking up oxygen and leaves them unable to send water and nutrients up to the plant.
A fungal disease called root rot moves into your plant, beneath the ground. The roots become brown or black, and mushy; the leaves become yellow and floppy; and the stem of the plant gradually becomes soft.
How to revive your buxus plant
It’s not easy to detect root rot in its early stages. If you notice that the leaves are yellow, check the moisture level in the soil. If it’s wet, then you need to expose the roots and examine them as well.
Dealing with root rot takes a while. I’ve written an entire article on how to do this. Please go over to Phytophthora Root Rot – prevention and treatment. This explains more fully what the fungal disease is and how to save and revive your plant from it.
First off you if you have yellowing leaves, read my guide here to deal with this problem, for boxwood with brown leaves, this guide may be more help
Box blight is another fungal disease. This one affects the leaves and stems. It likes stagnant, dark environments so it comes to rest in your plant if there’s a lack of air circulation or light. Although box blight doesn’t kill the roots of the plant (as root rot does) it does affect the rest of the plant. The leaves turn brown and then fall off. You see black streaks on the younger stems which then sometimes die off. And there may be fungal white spores on the bottom side of the leaves.
How to revive your buxus plant
As soon as you notice the problem of box blight, cut off the affected parts of the plant with a sterilised and very sharp cutting tool. Don’t throw these diseased parts in your compost pile as the disease easily spreads. If possible, burn them. Sterilise your knife or pruners before removing the next part of the plant.
Prune your buxus tree (sterilised cutting tool again) regularly so that air flows freely through the plant. You may need to take out older branches from the interior of the plant to allow air and light to get into there. On the other hand, don’t prune too much as this encourages new growth which is not the point of this exercise.
If your plant has a light infection of box blight, remove the infected parts and then spray the tree with fungicide to discourage more the of the disease from moving in. However, this cannot absolutely prevent any further attacks. Give a dose of fertiliser to the plant to help its recovery.
If it’s a heavy infection, you may have to discard the whole tree for the health and safety of the rest of your garden.
Reviving your buxus plant after bugs and other pests have moved in depends on the type of insect the plant has attracted and how early you catch the infestation.
Box tree caterpillars are relatively new to Europe and were first noticed in UK gardens around 2011. They eat the leaves of the buxus shrub and can cause severe leaf loss. You will notice the white webbing spun on the leaves and adult white winged moths. These caterpillars also like to eat the bark of the plant.
Box suckers suck the sap from your buxus leaves, especially the tips of the young shoots in spring. This results in minor damage but can weaken the plant. You may notice a white waxy smear of liquid left on the leaf to show that these insects are around.
Red spider mites are a kind of spider that are less than 1mm in length. You probably won’t see them individually but they do hang around in groups. During summer, these pests feed on the sap in your buxus plant. This gives the leaves a mottled appearance and, in severe cases, can lead to leaf loss. Look on the underside of the leaves for tiny greenish-yellow mites. Use a magnifying lens if needed.
Scale insects also are sap-sucking insects. They zoom into your buxus plant’s stems and leaves, particularly the underside. Some species of these insects excrete honeydew as they eat. This is a clear, sweet, sticky substance that doesn’t harm your plant in itself. But it does attract ants and the fungal disease called sooty black mould.
How to revive your buxus plant
First of all, isolate the plant from other plants to stop the spread of the insects and pests.
Then, cut off the infested parts of the buxus using a sterilised and sharp cutting tool. This may mean cutting away a large part of the plant. If you’re left with only a few branches, you can choose to discard the whole plant and start again with a new one.
Except for box suckers which you can leave alone as they do minimal harm, you can try to revive your buxus plant by using an organic horticultural oil on your buxus plant. Try neem oil or pyrethrum oil.
If this doesn’t work, try a neonicotinoid insecticide acetamiprid, for example Bug Clear Ultra. This is especially formulated to remove red spider mites.
If all this fails, you need to get rid of the plant. It’s preferable to burn it instead of dumping it in your compost pile.
Revive your buxus by pruning
Whatever the problem with your buxus plant, pruning it to let air circulate and light reach all the branches will help revive it. It’s best to prune them at least once a year, either between the middle of May and August to encourage growth; or from the end of August to the beginning of September to reduce the risk of box blight for established hedges.
Make sure to sanitise your pruning shears before use and in-between cuts. This stops any pests and diseases from being moved around the plant. And be sure that your cutting tool is really sharp. You need to make cut one pass per cut. Hacking at the plant just creates open wounds that let in diseases.
Fertilise plants that you’ve just pruned to help them recover from the shock.