Today I attended a lecture on boxwoods titled “Boxwood culture, pests and care“. Dr. Bruce Fraedrich delivered the lecture as part of the Bartlett Client Training Seminar. It was an invitation only event for Bartlett clients. A great idea!
I was fortunate in that my boss declined his invitation and sent me instead so I could earn my ISA and BCLNA education credits.
At work we regularly plant and shear boxwoods so this was a great lecture to attend. Below are highlights from my notebook.
Why boxwood
Why boxwood? It’s a tidy, slow-growing and well-behaved plant. It’s a “hot” plant popular with landscape architects and designers. One key characteristic is that it is deer-resistant. Deer browsing can be a big problem in some areas. It seems the deer just sample it but since there are many animals doing it, it leads to problems.
Boxwood prefers part shade; morning sun and afternoon shade. It loves well-drained, slightly acidic soils. Which is why it does well in the Lower Mainland.
It should be protected from winds, especially in winter. It also tolerates pruning. That’s why we can prune it into formal shapes.
Problems
Poor soil drainage can be a problem. Same for excessive irrigation. Boxwood is a dry site, understory plant in the wild. Too much water is a problem.
Boxwood can also be affected by low temperatures. If you have a long fall and then suddenly freezing temperatures, you can see desiccation damage. The plant looks ugly but should recover.
Pests
Boxwood can be affected by psyllids, leafminers and mites. All of these are treatable.
Volutella or boxwood canker can also be a problem. You can avoid this problem if you maintain vigorous plants.
Boxwood blight
Boxwood blight disease has arrived in British Columbia but we can live with it. It’s not the end of the world. There are now more resistant varieties available.
The blight is a fungus on leaves that leads to rapid defoliation as it spreads to twigs. It favours dense, crowded conditions and shearing. Shearing? It turns out that the blight produces sticky spores which then stick to power shears, pruning tools, shovels, soil and gloves. The spores can remain in the soil for a long time. So when you remove sick plants also remove the soil.
Sarcococca and Pachysandra are also affected.
Key research finding: majority of affected plants were sheared! That means the power shears are contaminated or they spread the disease.
To disinfect tools, alcohol-based Lysol is recommended. Remove soil and plant debris from your tools, spray them and allow them to dry.
Don’t forget to wash your hands, rubber boots, gloves and even hoses.
Fungicides are effective in treating boxwood blight.
Planting new boxwoods
Dr. Fraedrich recommends taking new boxwood plants and “parking” them on your site and monitoring them. If they look fine, plant them where you want them.
Pruning
Boxwoods tolerate shearing. In British Columbia it’s best to prune them in spring before new growth appears. Don’t touch them in summer. One insurance idea is to treat the boxwoods with fungicide right after shearing.
New resistant varieties
We are advised to NOT use English boxwood. It does fine and then declines. We don’t know why exactly that it.
A good boxwood for formal hedging is the dwarf Korean boxwood, Buxus sinica var. insularis ‘Nana’. Also good is Japanese boxwood, Buxus microphylla var. japonica ‘Green beauty’. It grows taller 7-9 feet. For mid-range height use Buxus ‘Green velvet’. Asian boxwood varieties are more blight resistant. Check to see if they are available in your location.
I will have some things to think about when I visit my client. See hedge below.
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