Frost Damage—A confusing problem without pest or disease
If you’re seeing spotty dying of branches in May and June, here and there, but particularly on one side of the tree…think frost damage.
Weak trees, particularly those with weak or few roots, will be more susceptible to twig death. The tissue was damaged months ago but we only see the change in color and wilting now. The buds of pines will get soft. The healthy ones elongate while frost damaged ones stay there as if paused, feel soft to the touch, and the needles turn gray-green. One shoot may be affected and the surrounding shoots show no problem. Whole branches on deciduous trees wither and never shoot out.
The tissue damage is evident on evergreens by the loss of chlorophyll. Frosted hard one or several nights in a row, and then the sun comes up and burns one side of the leaf or needle. The morning sun side of the tree will show damage months later—-now, as the weather heats up—when there was little evidence at the time.
Usually it is only weak trees that will be affected by this. Next year, try to give such plants more overhead frost protection.
I leave for work early in the morning. I thought that the sun’s rising in 1/2 hour would burn off the frosty morning air so I uncovered all my plants. This was a mistake and I have suffered about a 15% loss. Here in Michigan the frosts have been lingering into June and the forcasts are inaccurate. Protect your bonsai well into the morning hours long after the warming sun….you will be glad you did!