A blight on all your boxes

Outdoor Living

BOX OF TRICKS Common box, or boxwood, is used for hedges, borders, and topiary figures.

A recent disease will leave your box plant feeling none too clever

In the garden
Frank Steffens

A common sight in many Mayo gardens, Buxus sempervirens – boxwood, or common box – makes a fabulous hedge or border, forming a dense, evergreen screen of small, rounded, lustrous, dark green leaves. It’s a great one for topiary too, allowing creative types to go wild with shapes, from globes, cones and spirals to birds and animals.
However, boxes can be affected by a very particular disease. Box blight. You might like to impress your neighbours by calling it ‘Cylindrocladium Buxicola’ and to sound extra clever you can call it by its new name ‘Calonectria pseudonaviculata’. It doesn’t change the outcome, but it might make you feel like an expert.
I’m afraid I can call myself a bit of an expert on this topic; it’s not that I ever wanted to be, it just happened.
That’s the thing about gardening, it doesn’t matter if you are an amateur or professional, you will constantly learn, whether you want to or not.
I’m not sure how much of a gardener Samuel Beckett was himself, but to quote him – ‘Ever tried. Ever failed. No matter. Try again. Fail again. Fail better’. That kind off sums up the reality of gardening. It is a process through which you learn to understand.
But back to one of my favourite diseases, box blight. Here in Drimbawn Garden, Tourmakeady, we have had the displeasure of fighting this disease over the last 12 years. It is a war that is almost impossible to win, as so far, there is no cure for it, but there are some fungicides on the market which help to keep it more or less under control.
Box has been used for centuries now without too much trouble. The first cases of box blight were recorded in the UK in 1994, and since then it has spread all over Europe.

Symptoms
•    Light to dark brown spots on the edges of older leaves, getting darker towards the centre.
•    Orange to brown spots on younger leaves. If younger leaves are infected, older leaves are less likely to get infected.
•    Black stripes along the shoots.

A few days after the first symptoms appear, a massive leaf drop can be observed and shoots will die off.
Luckily for the fungus and unluckily for us, it loves the Irish climate. Temperatures above 5°C and below 30°C are perfect (33°C would actually kill the fungus). If the leaves are wet for a few hours, the spores can infect a healthy plant through the cuticle layer (skin) of the leaves and within another few hours they will start to germinate. The spores can live as long as four years on dead leaves – this fungus is just as happy as a pig in mud in our climate, a very small pig.

Actions to take
Hedge hygiene is crucial. Unfortunately for us in Ireland, avoiding wet leaves is one way to answer the problem. This at least is good advice for those growing their hedging in the house. A more practical solution would be to only prune on dry days, and if you do cut your hedges make sure to disinfect the tools.
After pruning, gather all leaves and cuttings and burn them. Don’t put anything into the compost because remember, it stays active for four years – which is longer than many governments can claim.
Make sure the plants are well aerated and fed. I mainly use seaweed dust or liquid seaweed, as well as an organic 4-3-7 NPK (nitrogen, phosphate, potassium) fertiliser. It helps to avoid using artificial fertiliser; they don’t add any substance to the soil and quite often just stimulate an unhealthy growth.
If your boxes have already been blighted by the fungus, add these to your to-do list. Two fungicides I use are Signum and Switch. The odd Rose Clear is useful too, but not as effective as the other two. The best known treatment is a product called Topbuxus, and this is a combination of fertiliser that is rich in nitrogen and copper, which acts as a fungicide. I make up a similar mix myself, but keep the nitrogen level low, as we want our plants to grow strong, not just fast. If the situation turns nasty, just cut down your plant by a half and destroy all off-cuts.
But there is light at the end of the tunnel – and that doesn’t come from the approaching train. Some new Buxus varieties are on the market: Herplant Bvba, a company that was founded in Belgium in 1985 and specialises in Buxus, has about 200 different species in their catalogue. Four of these varieties are resistant to box blight: ‘Renaissance’, ‘Skylight’, ‘Babylon Beauty’ and ‘Heritage’.
The only question now is, where and when we can get these in Ireland?

Frank Steffens, is head gardener at Drimbawn Garden in Tourmakeady. Drimbawn is a member of the Clew Bay Garden Trail, a chain of beautiful and unique private gardens that open to the public during summer to raise funds for charity (see www.clewbaygardentrail.ie for more). Each month an article by a trail member will appear in these pages.