Bonsai Care Autumn Newsletter 2014
The summer itself can with some certainty be described as long and hot. The temperatures made working outdoors very enjoyable. Watering our large collection of trees required considerable attention, for much of the summer we were watering twice a day – in the morning before the sun was bearing down on the trees and again in the late afternoon. I have read many times about leaves being burned by water droplets acting as tiny magnifying glasses, though in the past I have out of necessity watered at midday and never had any problems. What we do watch for is sun-burn on the Japanese Maples. Some of our outdoor benches have full-sized trees above them which have been very useful in providing shade during the sunny days. I think that we be erecting a pergola during the winter so that next year we can cover some of the outdoor area in green shade netting. The trees could probably do with cutting back as they block out a little too much sun. Dappled shade is ideal for many bonsai, whereas too heavy shade will cause the trees to grow toward the light; and so need turning frequently.
Anyway, thoughts for the autumn.
Watering can be reduced down as the weather starts to cool down. It has been tempting to water almost by rota during the summer, either automatically once or twice a day, as part of a routine. You’ll probably feel the same, watering in the morning, perhaps before work, then again in the evening. This will have mostly been fine in warm weather as the trees probably needed it. Now however your bonsai may not have dried sufficiently to require watering again, so do check by touching the soil surface to see how dry they are and if watering is required. Don’t forget as well that bigger trees in larger pots dry out much less slowly than small bonsai. Judgement is required to avoid over-watering.
Feeding should also be reduced. I use Naruko slow release fertiliser on lots of the outdoor trees. I use three applications of this per year, placing a light covering of the granules onto the soil surface in April, June and August.
In October, we stop feeding any nitrogen to the bonsai. Some tomato fertilisers have zero nitrogen which is easily available from garden centres. An application or two of low nitrogen fertiliser helps the trees to harden off any green shoots (reducing frost damage) and has a number of other subtle benefits.
Remember to check your wiring on your bonsai trees. Trunks and branches can thicken quite suddenly at this time of year and wires can cut in.
Wild native trees will be seeding, so collect some if you want to grow from seed.
The leaves on deciduous trees will be falling on the soil surface, so remove them as they can harbour pests & diseases. Leaves can also get caught in the branches, so pick them out if this happens. Trees kept in full sun will tend to have brighter autumn colours than ones kept in shade.
Some people repot bonsai trees in the autumn. Although I have done this in the past, I think spring is the better time for most bonsai.
Any shade netting you have erected to protect trees from full summer sun should be taken down. Heavy snow presses down on the netting in winter.