Winter woollies for trees
A couple of weeks ago I noticed that some of the college and city trees had received a fresh coat of whitewash. Last year I saw some of them being painted. Given its really cold with temperatures below freezing at night I wondered why. It is common in tropical areas and from what I had heard in the past was that’s to repel borers.
Whitewashed tree
I consulted the internet which produced a range of answers, many to do with sunburn and borers. The answer which made sense in the circumstances was this. The white reflects light and prevents the trunk heating up too much during the day. This minimises diurnal heat variation, splitting and damage to bark and thus helps keep the tree healthy. It’s like lip balm for trees. On my trip to Qingdao I also noticed that many lined the two lane roads and the white acted as roadside markers in the dark.
Some of the other local trees have trunks wrapped in a coarse rope with varying degrees of attention to detail. I found one also encased in plastic.
Rope wrapped trees in Xingtai
Rope and plastic
A weekend in Beijing where the weather is even harsher produced a greater variation in winter tree and shrub support. It included wrapping with rope and some kind of synthetic fabric, emplacement of the equivalent of a plastic greenhouse and specially constructed covers some of which had capacity for opening.
Wrapped tree at the Summer Palace in Beijing
Wrapped tree at the Summer Palace Beijing
Tree covered by a greenhouse at the Summer Palace
Zhengyangmen Gate in Qianmen with covered shrubs
Multiple wrapped trees near Qianmen
Wrapped tree outside a small shop in Dashalan St. Qianmen area