Preparing for winter – Bonsai Tonight

November 20, 2009 by Jonas Dupuich

I’m lucky – I live in an area that doesn’t get too cold in winter. This makes late fall, winter, and early spring the busiest time of year – a time filled with cutback, needle-plucking, wiring, and repotting.

I was thinking, this afternoon, of what I can do to make my pines as vigorous as possible next year. The first item that came to mind was fertilizing early. While repotting season runs through February and occasionally into March, there is generally a 24-30 day gap between repotting and fertilizing to give new roots a chance to grow before they’re presented with food. If I repot in February, I can fertilize in March.

To get a jump on this, I need to repot on the early side. Which means I need to cut, pluck and wire my pines as soon as I can get to them before I repot. And before I can repot I need to get all of my supplies in order. This is why I’m spending a beautiful fall day washing, sifting, and mixing bonsai soil.

Ready Mix

I’ll skip past the potential ingredients of good bonsai soil and skip to the important part: they must be clean and dry. The photo below shows the pumice I use as purchased.

Unwashed pumice

Great soil medium, but very dirty in this case. Pumice is very light – important when repotting large bonsai – and it retains enough moisture to make it a good ingredient for most mixes. You can use more in wet areas or for trees that require less water. You can use less in arid areas or for trees that like water. The goal, in either case, is to get it looking like this before using it:

Clean pumice

Which, again, is why I’m washing bonsai soil today. I usually clean and dry my bonsai soil over the summer so all’s set by now, but this summer was busy and now is my last chance before repotting begins.

All of the ingredients I use in bonsai soil, save pumice, come clean enough for me to simply dry and sift before using. Drying alone doesn’t always cut it for pumice. For most of my 15 years in bonsai I’ve been washing it with a setup something like this:

Bonsai soil washing station

I fill up 5 gallon buckets of dirty soil and pour some into a soil sifter set in a tub of water. I rinse the soil in two of such tubs to wash the fine particles away and pour the remainder into a container that drains well so the soil can dry.

Wash

Rinse

Repeat

Removing these fine particles is necessary to promote healthy growth. Fine particles impede drainage which limits the amount of air, water, and fertilizer one can supply to bonsai. Limiting these limits overall growth and vigor for young trees and old. Good health starts with the roots and without good health there is no good work. This is why good bonsai begins with repotting.