Replanting preparations, (Box Blight), Winter Task 5

Moving on with my winter tasks, I had the delivery last week of  fifty very healthy looking box plants, (Buxus Sempervirens) all about 200mm in height in 7 cm pots.

Box blight ( Cylindrocladium buxicola) is an airborne fungus. The spores are mainly spread from water droplets dispersed in the wind. I recall seeing  a particularly bad case of this when I worked as an under gardener for the National Trust on the very low box hedge of Buxus suffruticosa. Unfortunately, in this particular case, the spread had been made worse by the use of the irrigation system.  The initial browning and dying back of the leaf tissue was followed with the entire tops of the hedge, in some parts completely bare, with exposed woody stems, with little foliage left around the edges.

Some hard trimming had taken place in an endeavour to rejuvenate parts of the hedge, however this was not very successful. Because of this past experience I now keep a close inspection on the box hedges in the Victorian walled garden in which I work. In general, during my first four and a half years in this particular garden, I have managed to keep the fungus to a minimum, and I have always taken great care when using trimmers or sheers, not to transmit any existing spores to other parts of the hedge. 

Last year I noticed, however, an increase in the spread of  box blight which gave rise to my taking some further action in order to minimise the spread. Over the course of this winter, therefore, I have been removing dead sections of the hedge  with the use of a hedge trimmer, cutting the areas down to stumps. I have then dug up the stumps and removed them to burn. After I have undertaken this task all the tools that have been used are cleaned with a horticultural disinfectant  to reduce the chances of any further spread when I come to use these tools again.

Within the gaps of the hedge which have been created as a result of the removal of the infected sections of hedge,  I have been removing a layer of soil this week, to a depth of about 100mm. The reason for doing this is to remove any resting spores that may still be within this area of the soil. I have then moved fresh soil into these sections from another part of the garden. I don’t plan to undertake the planting of the new box plants until early spring when the soil will be warming up, which would be the best time to carry out this task.

In the meantime these healthy new plants are in the cool end of the glasshouse, but they were in need of being potted on into bigger pots. This week I have potted the plants into 1 litre pots using an organic peat free compost. They will remain in the larger and cooler section of the glasshouse until the stage of planting out. They won’t be in these pots for a sufficient length of time to establish their root systems. The main objective at this stage, was to remove the plants from the smaller pots, as it was evident that roots were forming on the surface with some of the tips of the plants starting to turn yellow.

With a view to the spring planting I plan to space the plants, where possible, 300mm apart. This is a wider spacing than I would normally plant, which would be about 200mm apart. The reason for this is to improve the air flow around them as poor ventilation can increase the spread of the disease. Once the plants become established the challenge is to clip by hand repaired areas of the hedge in an attempt to reduce the amount of leaf spread. This will not be easy as, once it is established, box forms a tight knitted structure.

Interestingly, I was listening to Gardener’s Question time on Friday 17th February, on Radio 4, when The Head Gardener at The National Trust property Levans Hall in the Lake District was being interviewed, and one of the topics was box blight. He was explaining that the garden had experienced a bad case of the fungus and that a lot of the plants had been removed.

However, he went on to say that they were not going to replant with box plants, but instead Ilex Crenata (Japanese Holly). He had expressed his concerns about the resting spores, which I have already mentioned, and that the alternative planting would be a safer bet. He didn’t mention, however, the method of removing areas of soil as outlined above as an alternative practice in which to continue with the planting of box.

It will be interesting to see what results I get once I have undertaken the whole replanting process.

NEXT BLOG – ROSE PRUNING, MOVED TO WINTER TASK 6