Some years ago, we fell for a Korean fir tree in a local nursery.
We had gone along, as one does, intending to do little more than walk round, possibly picking up the odd pot plant or some fertiliser or pesticide that was in need of replacement … and there it was, resplendent in the largest plastic pot we had ever seen outside a botanical garden, one splendid Korean fir, complete with a label explaining that the species is a small to medium-sized evergreen coniferous tree which is native to the higher mountains of South Korea. Why we thought that it was a good idea to buy the most expensive tree in the centre, and a tree that really belongs to higher altitudes than that at which we dwell is hard to explain; and the best that I can do is to say that we liked its smooth, grey-brown bark, its thick, glossy needles … which are really leaves … and its purplish, upright cones, which even quite young trees produce, although the cones of mature trees are more grey-green in colour. In short, we did what I recommend gardeners not to do; we bought it on impulse, and a pretty expensive one at that. But we have never regretted our failure to resist temptation, for our Korean fir is happy in Polmont, has grown steadily more attractive, likes our soil and our climate and is now a splendid example of what we have subsequently learned is a very popular ornamental plant in gardens.
But a recent news item about needle blight sent me to my computer to discover if my attractive tree is at risk. Scots pines, I heard in a news bulletin, are at serious risk from Dothistroma Needle Blight, also known as Red Band Needle Blight, which is caused by the fungus Dothistroma septosporum. Apparently, infected needles develop yellow and tan spots and bands, which soon turn red. After mid-summer, the infected needles are lost and trees are left with only a tuft of the current year’s needles. Untreated, this needle loss will gradually weaken the tree and may eventually kill it. The Scots pine had been thought not to be at serious risk of infection by Dothistroma septosporum: but two years ago the disease was found infecting pine plants in three forestry nurseries in Scotland; and since then there has been an alarming spread of the problem throughout Scotland.
So, although Dothistroma septosporum is seen as affecting pine trees, might my Korean fir be at risk? And I learn that a fungus called Sphaeropsis sapinea is found in Korean firs, where it turns the needle tips brown and causes cankers on twigs, making the tree susceptible to attacks from insects or other diseases, while a second fungus … Phomopsis juniperovora … causes the ends of the needles to turn yellow, then brown before the fungus advances into the stems and eventually kills the whole branch. Not nice: but it seems that my Korean fir is not presently at risk from the spread of Dothistroma septosporum, to my relief.
But, given that Dothistroma Needle Blight was unknown in the United Kingdom prior to 1954, the year in which it was first found in England; given that experts believe that gradually rising temperatures north of the border could be behind its spread; and given that Scots pines were thought to be pretty well immune to the disease until recently, I wonder whether my Korean fir is as safe as I hope it is.
The words ‘climate change’ feature regularly in these columns; and I have no doubt that we are experiencing rapid climate change which will bring new challenges for the plants in our gardens, our parks and our countryside. When the Forestry Commission talks about the possible need to spray Scottish forests with fungicide from the air and warns that this could make the problem worse if the fungus proves resistant, we should all sit up and listen.
Sandy Simpson, Polmont Horticultural Society