Nights may be too cool now for semi-tropicals. Move deciduous trees to a shadier location to prevent new growth. Watch the weather reports more carefully now. It is common to have an early frost. The average high is 71 degrees; the average low is 44 degrees. The record high is 87 degrees (2015 update: expecting 90° on Oct. 2); record low is 22 degrees. The relative humidity averages 43%.
Watering: You may cut back on water depending of the temperature, but do not let them dry out completely.
Fertilizing: Half normal feeding. No nitrogen. (Check out John’s recent screed on fertilization.)
Trimming & Pruning: Trim strong growth on upper portions of conifers. Trim and clean off dead needles. After leaves have fallen from deciduous trees, it is safe to shorten the year’s growth. Clean all dead leaves from soil. At the end of the month, remove all fruit and any seed pods. The berries may be saved until spring if the tree is healthy. Trees may be rewired for winter.
Winter Care: Prepare the cold frame with snail baits and insecticides; purchase fresh straw. Prepare ground for those bonsai that will be planted for the winter. Leave the trees out as long as possible to insure they’re going dormant normally. Toward the end of the month, remove them from their pots without disturbing the roots any more than necessary and plant the trees in the prepared ground. Sprinkle pill bug bait generously and cover with straw. Those bonsai that are to be stored in the cold frame for the winter should remain in their pots.