My article about early leaf drop in Silver Birch trees is very popular – but it has really peaked this year (2018).
My own trees started going yellow this time around in mid-June. After a lot of research, I concluded that it was due to heat stress as a result of the prolonged warm weather and low rainfall we have experienced. I know that some places have had torrential downpours, but it isn’t enough. The temperature has remained pretty much in double digits the whole time, and has been in the mid-20s and low-30s most days for almost two solid months, and with no end in sight.
I commenced deep watering right after I found it as a remedy in June, and it has worked like magic. Right now, I simply set the sprinkler going for about an hour in each of three separate locations, and I do this each night (next year, I’m going to install deep-watering spikes to help the water get deeper into the soil). I have also found a way of watering and fertilizing at the same time.
When trees are stressed as a result of high humidity and low rainfall, they can’t get enough water and begin to shut down just as they do in the Autumn. It doesn’t kill them unless it happens year after a year, but obviously you can take steps to deal with it once you notice it.
One thing I have noticed with the benefit of hindsight is that the foliage on virtually every Silver Birch I have seen this year is thinner than in previous years (that’s also true for a lot of other trees I’ve seen). The leaves are actually smaller. The reason I say “hindsight” is that about a month into deep-watering and my tree has put out some significant new growth and the leaves on that new growth are much larger, and just like the photo I took last year.
Note that we have no hosepipe ban, and I wouldn’t be doing this if we did.
Once I commenced the watering, the yellowed leaves all fell over the next week or so, but no more were produced. Right now, not a single leaf has fallen in the last month at least and the whole tree is green with the aforementioned new growth. It is also producing fat catkins.