The Facts about Box Blight: But have I really got Box Blight?

I’ve lost count of how many calls we’ve received from anxious gardeners who, noticing some discoloured leaves on one or more of their Box plants, have convinced themselves that Box Blight has struck…Even with the spread of the disease, though, the chances are that something else is to blame. So, before you tear out your hair and contemplate doing the same to your Box, here’s a checklist of more common causes:
Irregular watering will eventually cause the whole plant to brown and defoliate. New growth will only be visible at the shoot tips.
Under-watering can result in brown patches appearing.
A starved Box will turn an orangey yellow – not a colour associated with Box Blight. Container grown Box are far more likely to be detrimentally under-fed and a light annual sprinkling of a proprietary fertilizer (powder or slow-release pellets) should fix the problem.
However, as we will see in the next post, any soft growth on any plant that has been encouraged by adding high levels of nitrogen has been shown to be more susceptible to fungal diseases. Therefore, only feed when absolutely necessary and, even then, keep a steady hand.
As noted above, Box Blight does not result in foliage turning any shade of yellow/ orange / red. Besides a lack of feed, other causes of such changes include:
• Sunburn
• Stress following hot, dry spells in summer (general bronzing or orange foliage)
• Roots damaged by waterlogging in winter
• Waterlogging particularly if planted in clay (yellowing foliage)
• Low temperatures in winter (yellowing of leaf tips and margins)
Young growth can be caught by a late frost in spring resulting in pale brown and papery-looking foliage.
There is a big difference between shade and darkness. Box may not worship the Sun with the same unabashed enthusiasm as Lavender or Rosemary, but it still needs light. A Box (or part of a Box) starved of light will slowly deteriorate with foliage looking increasingly limp and lacklustre and eventually dropping.
Dogs, cats and foxes like to mark their territory but are incapable of distinguishing between a lamppost and, say, a pair of Box Balls in containers. Unfortunately, their pee will do a lot more damage to a Box than to a piece of municipal street furniture.
Any foliage in the firing line will brown, blacken and die – but new growth will eventually appear. However, the area at risk will almost always be at the bottom of the plant – unless you have a Great Dane or St, Bernard
If a frost follows shortly after Box has been cut, the outer leaves will die, leaving the surface of the plant a distinctive white. Trimming no later than September should leave enough time for new growth to harden off before the frosts start.
Wind can scorch Box leaves, tuning them brown. However, unless the plants are situated in a truly windy location, this is unlikely. The good news is that if it is windy enough to scorch your Box, it’s windy enough to deter Box Blight spores from settling on them.
Picture: A Box hedge with severe winter-weather damage