THE MODERN MINT BLOG
Boxwood is one of our absolute favourite plants. The evergreen leaf that shines in winter, the smell as you clip it, the brilliant shapes you can make from it… but it is suffering somewhat from two major problems:
- Box Blight
- Boxwood Caterpillar and Moth
None of this is the be all and end all for boxwood, but it helps to be aware of it and know a little about what you can do should either of these problems arise.
Boxwood Caterpillar & Moth
I hadn’t seen this in a garden I worked on until this spring, when a client I visited in Essex showed me these odd looking green caterpillars. Ah, yes. The boxwood caterpillar.
They will defoliate your boxwood and can leave it exposed to fungal attack. Not great at all, but not impossible to get rid of. Knowing what we had to contend with in the Essex garden, we have taken the following steps:
Clawed away the webbing made by the caterpillar pupae. To do this I wore gloves and scrabbled at the boxwood plants like a dog digging for a juicy bone, or a petulant child throwing a tantrum. Not the most graceful of work, but it is how I looked as I broke the webbing up and plucked the caterpillars that were inside the webbing from the boxwood leaves. They were then dropped into a bucket of water with washing up liquid in.
Set-up a pheromone trap for the male moths, to reduce the number of fertilised eggs that may get laid by females.
This advice was given to me by Chris Poole, Chairman of the European Boxwood and Topiary Society, a brilliant resource of all things boxwood. Here is his advice giving you the lowdown on another option you can take for the caterpillar – spraying:
“The most effective spray is based on Bacillus thuringiensis (Bt) which is used in XenTari and is generally considered harmless to humans, birds, and other beneficial wildlife including bees. In some countries, including Australia, Canada and the USA a number of products have organic certification. You can buy domestic amounts of XenTari from Topbuxus.
A thing to remember about Bacillus thuringiensis based products are that they break down in UV light so only last on the plants for a maximum of 7 days. I have used it as a preventative if I’m going away for a couple of weeks and that has worked, but normally I only spray if there are signs of caterpillars.”
Go now to Topbuxus for your XenTari.
Having made these first steps in combatting the Boxwood Caterpillar and Moth, I will watch carefully what happens in the Essex Garden and see whether the destruction of the webbing needs to be repeated.
For loads more information please visit the European Boxwood and Topiary Society website. It is a fantastic resource for dealing with this pest. The Pheromone traps can be bought here too.
Box blight is a fungus that can cause dieback on your box plants.
Again, lots of advice is given here at EBTS – but in brief, here are some ways to handle the disease:
- Remove all infected plants and burn them. Do not add to your compost heap.
- Grow your own plants in-house. Some nurseries have stopped importing boxwood from abroad because they have found plants to be infected, whereas if they grow them from scratch they know exactly how healthy they are, from taking the cutting through to potting on and selling. If you are buying from a nursery and aren’t sure if it has blight, be careful. Some fungicides will suppress the blight, just long enough for you to buy it, take home and then lose the receipt. Then of course, the fungicide wears off and you are left with a stack of blight riddled plants. As with all gardening, take your time and have some patience to grow your own.
- Stop clipping your box plants and clear some space around them. They like air to circulate around the leaves, so give them the chance to breathe. The box will immediately look healthier!
- Mulch with homemade compost in the spring. This will also help trap moisture in the ground, meaning the plants get a more even amount of water through the year. Stressed plants are weakened plants, and so more liable to suffer from infections.
- If you clip your boxwood in hot, sunny weather, you may just have leaf scorch rather than blight. This is a yellowing of the leaves where they have been wounded. The plant will recover, but again it stresses the plant out. Which is not what you want.
- Give some fish, blood and bone around the roots in spring. Water the roots with Topbuxus or liquid seaweed to add health and provide nourishment every 6-8 weeks during the growing season, April to August. They say don’t water from the top, onto the leaves, because this will spread any fungal spores. But when it rains, this surely does the same thing? So it can’t really be stopped….can it?
Basically, defending the plants from blight is a simple job.
Remove diseased wood, or if starting work from a healthy plant, then make sure it stays a good, healthy plant with plenty of strength to draw on and has lots of air circulating around its leaves – and you will reduce the chance of blight taking hold and ruining your beautiful boxwood.
Charlotte Molesworth (my topiary mentor) and I also keep many of our plants healthy with Beneficial Microbes. You can read about them here. We spray a few times a year just to keep the plants in good health.
We hope this helps, it is a brief rundown but do check out the EBTS website as they have brilliant information on there about the boxwood caterpillar and how to deal with blight.
And don’t forget to enjoy your boxwood clipping! I certainly do…
I am running a topiary workshop in 2020 with the wonderful topiary artist Charlotte Molesworth at her spectacular topiary garden in Kent. This is a topiary workshop where you will learn to clip, so be prepared to do some cutting. We start with a tour of the garden, which Charlotte and her husband Donald have been cultivating for 34 years. It is organic, full of wildlife and has the most extraordinary pruned shapes made from yew and boxwood. You can see more photos of the garden in an article in the Guardian here: Topiary Garden In Kent What Else Will …
On Monday night I gave a talk to the Hardy Plant Society Middlesex. Below are a few links for further information based on some of the ideas discussed in the talk: Real Seeds – a fantastic supplier of fruit and vegetable seeds for growers. Boxwood Caterpillar Advice – from the European Boxwood & Topiary Society. I will also write a little companion piece this winter with more information and some topiary techniques, so watch out for that on this website. Boxwood Lure & Nematodes – my preferred option for dealing with the caterpillar. Discount code for 10% off is EBTSBOX29GBZ …