The Taskmaster explains what to do, how to do it and why for bonsaists in the San Francisco Bay Area.
December in the Northern Bay Area microclimates is an uncertain time. cold or even frosty nights can easily be followed by afternoons of 65° or so, and then the next three days could be rain. You just never know. but the truth is that it doesn’t matter. In your well-ordered garden world, you will be ready for whatever comes. Here’s how.
Our relatively warmer Winters means the trees never really stop growing. They may slow to a crawl, but during periods when the soil temperature warms a bit the roots grow a bit and the branches and trunks thicken a little. This means two major things: Number one is that the trees can be fertilized on a regular schedule and it just might do them some good come Spring. Big debates in some quarters about this, but many growers in mediterranean climates use an organic fertilizer (most of which are naturally slow-release substances) with low nitrogen ( all numbers in the below ten range) all year long. Number two is that unlike in colder climates, mosses, unhelpful fungus, and weeds, and even some bugs like ants and scale will continue to be a problem on a regular basis. Spray a fifty-fifty white vinegar and water solution on mosses and bark fungus during a dry day or two and it will all turn brown and much drier so that it can all be gently brushed away without rubbing so hard that the bark is damaged on trunks, exposed roots, and branches and crotches. Don’t miss the end of December and end of January dormant spraying, especially if you missed the end of November one. Horticultural oils of various types are industry standards in agriculture and they work great. Read the labels and measure exactly. The mixture is lighter by half for the trees like junipers and others that are still green and growing. This should kill scale and other overwintering critters so that you don’t have to fight bigger and more damaging groups of them later. Do a very thorough job and cover the soil with newspaper when spraying so the oils don’t enter the soil. Repeat the whole process if it rains within thirty six hours.
When it rains too frequently the pots should be propped up on one end to help them drain. When it rains too lightly, you have to go scratch at the soil with a chopstick to see if the water actually penetrated the soil, especially on evergreens and conifers. When it doesn’t rain, scratch again to make sure that the tree is really dry enough to need the water you want to give it.
When frost comes, or freezing below 36° for too many hours, put the pots under the eaves of the house or under their benches and protect from wind. Tropicals and the smaller pots and tender plants need protection when the temperature goes below 40°. But some trees fruit better or flower better if they get a light frost now and then, so just keep a close eye on the actual weather, not just the weather report.
Wiring this time of year on deciduous trees is possible, and some people do it, but if you injure the tree this time of year it will be very slow to heal, sometimes with ugly or even deadly consequences. And it’s easy to knock off buds and spurs that will be needed later. And there’s very little woody growth to make the wiring really worthwhile by the end of Winter. And you really shouldn’t bend big branches or make radical bends now. You may decide it’s best to just wait for the Spring push for deciduous wiring. Maybe stick to conifers and evergreens for Winter wiring.
Take some pictures of your trees against a North wall or in neutral light because the camera will make you see things that your eye misses. Prop them up on some bean bags to find a new angle or even a new design for the future and pull out that picture to use as a guide when you finally get to repot. Use the Winter to try to see future possibilities for your garden, for your trees, for your own life. The possibilities are endless, and none of it happens unless you take the time to think it through.
– The Taskmaster