Head Gardener's Blog: Box Blight
“Welcome to my new blog. The aim is to keep you up to date with what is happening in the gardens; be it a major project or just what is looking good at the time of writing.”
Blighted in Blighty
I would have liked to have started this blog on a slightly lighter note that the subject of box blight. However, blight has blighted us here at Riverhill and therefore this has been one of the winter projects this year.
As visitors to Riverhill might know our vegetable beds in the walled garden are lined with box hedging (Buxus sempervirens). The Walled Garden was completed and planted up in 2012. The box used was actually a dwarfing variety, Buxus sempervirens ‘Suffruticosa’, and had taken many years to knit together and make a fully formed hedge.
I had personally taken great pride and care in cutting and feeding these hedges over the past three years, only for disaster to strike late last year! I was tending to the vegetables in late September when I first noticed the tell-tale signs of box blight, small areas where the leaves were turning brown. Unfortunately, in late 2019 the weather was conducive to the rapid spread of the disease and by late October the blight rapidly spread through over half of the hedges.
Blame the weather!
Boxwood blight - image courtesy of Leonora Enking
As you may remember we had plenty of rain in the autumn and winter and this, along with moderate temperatures, created the perfect humid conditions that accelerated the spread of box blight. Another contributing factor to this rapid spread was the fact that a dwarfing variety of Buxus was used. Although Buxus sempervirens ‘Suffruticosa’ creates a lovely dense small hedge, perfect for lining the vegetable beds, it also provides a breeding ground for pests and disease. It creates such a dense hedge that there is little room for air circulation in and around the plant, therefore increasing the humidity.
Box blight affects the leaves and stems of the plants and, as such, can actually be controlled as it does not affect the roots of the plants. However, it does mean any infected areas have to be cut out and it looks rather unsightly for some time afterwards. So, it was decided, as this is one of the formal areas of the garden, to remove the box and replace it.
Planting alternatives
The first question then is what to replant with - box? you may ask. Well this wasn't even considered as the spores of the fungus that causes box blight, Cylindrocladium buxicola, can remain in the soil for at least 6 years. That, along with the fact that Buxus is coming under threat from a new pest; the box tree moth, led to the decision to plant with something that has similar characteristics to box, but with less (current) pest and disease problems.
If you were to look up alternatives to box hedging, I’m confident you would find websites suggesting up to ten alternatives, ranging from yew (Taxus baccata) to lavender (Lavendula angustifolia). However here at Riverhill a lot of those would not work as the hedges need to be very dwarfing to create almost a parterre effect around the vegetable beds.
I looked at two alternatives: Lonicera nitida and Ilex crenata. Lonicera nitida is a plant in the honeysuckle family and when clipped can create a lovely hedge. It is very hardy and also suffers from very little pest and disease. It's only downfall, at least for this situation, is that it grows ridiculously fast. Meaning it would need clipping three or four times in a season in order to remain looking tidy.
Ilex crenata is in the holly family, Japanese holly to be precise. Now I'm sure most of you reading this are aware of holly (Ilex aquifolium), I’m even sure many of you seek out a holly tree in December for its red berries and prickly evergreen foliage to add to festive table decorations or wreaths. So some might be asking if I’ve gone mad. In fact Sarah raised an eyebrow when I first suggested it. However Ilex crenata has small wavy toothed leaves, 2-3cm, that does not resemble its cousin aquifolium. It also is slow growing, forming a shrub or small tree if unpruned. However, if pruned it will keep a nice tight form that is ideal for topiary. It also has fewer pests and disease than box, with the only thing of note to be aware of being black root rot. It is also worth bearing in mind is that although Ilex crenata is hardy the roots do not like to be frozen when in pots, however they are fine when in the ground.
And the winner is…
With that decided I ordered over 500 Ilex crenata plants in late January for delivery in February. Typically, upon arrival we then got the first cold nights of the winter. The plants were protected overnight and hastily planted over the next two days to ensure that they weren’t affected by the cold or blown away in storm Ciara. Hopefully over the next few years they will flourish to replicate the nice tight hedge that they were brought in to replace.
Look out for their progress when you next visit and I look forward to seeing you in the Gardens soon!