The Taskmaster (aka Chris Ross) explains what to do, how to do it and why for bonsaists in the San Francisco Bay Area.
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August 
August in the Northern Bay Area microclimates is a time of wondering what next. When the temperatures go above 85° or so, the trees shut down transpiration to conserve water, and even though the surface of the soil can seem dry the rootball may stay quite moist because the tree has stopped drinking much. Wind can further dry the foliage, and there’s your burnt leaf edges and seared tips, right there. Scratch the soil with a chopstick to see how deep the dryness goes to find out how much water to add and when. If you repeatedly add of water and the tree keeps slowing down and never drying out, the constant moisture and heat will grow fungus, mildew, and rot. You have to figure out a way to consistently let the soil get nearly dry and then add moisture, not an indiscriminate flood. And constantly wet soil with fertilizer in it is even worse.
When the days get too hot, remember that afternoon sun, even fairly late sun, is hotter and drier than any other time. Move tender trees and small pots to the East or even the North side of a house, fence, shrub, hedge, or tree for the hottest days. Some growers submerge the smaller pots in a cheap plastic colander or basket full of pumice or lava for the hottest months to keep the roots cooler and to slow their drying out. to reduce the effects of wind and leaf burn, you can mist if you have shade cloth or other bright shade, but it’s not a good idea in bright sun. One solution is to spray with Cloud Cover or other protective sprays. Eleanor’s VF-11 is a good leaf spray product for all plants that can be used in full sun, and is a very good means of foliar feeding, too.
Pots that are especially slow to dry may be getting rootbound. The roots grow at least as fast, if not faster than the tops of plants, and by August the poorly-draining pots are beginning to become noticeable. Get a Phillips screwdriver (good grip, slender shaft, pointed tip and smooth surface mean fewer roots damaged) and poke it down through the soil to the bottom of the pot in lots of places to conduct air into the roots and promote better drainage. Mark these pots for earliest repotting when it’s safe, usually January or February.
All the sun and heat means now is a good time to work on jin and shari. Dead wood needs to be protected and hardened Lime sulfur solution is the best for the job, and the sun will bake it in and bleach and sterilize the wood. Apply it with a brush or Q-tip for small areas, a bigger brush or corner of a sponge for larger areas, and keep it off the bark, leaves and soil. If it seems too white and bleachy for your taste, add a few drops of India ink to a quarter cup and reapply.
Bugs are in full glory right now, so use the “fan” setting on a hose-end garden nozzle to spray over and under all foliage and bark now and then for mites and aphids. Bait for ants even if you only see a few. Spray Ortho Max and Malathion and other sprays now and then if and when it seems necessary, but switch around because lots of bugs can become immune to products used too consistently. Best time to spray is evenings and very early mornings so sun and heat won’t cause chemical burns on the leaves. Always protect the soil and shake off excess from the leaves.
Any wiring done earlier is likely to be cutting in by now, and earlier growth may be hardening off, so this is a good time to remove tight wires and to wire or rewire new growth. And here’s the kicker: This is the only chance you get at it, so you have to go do it now. If the new growth gets just a little too thick while the Summer slips by, especially on deciduous trees and broadleaf evergreens, then it won’t be flexible enough to wire it properly and you’ll have to cut it off, grow some newer new growth, and try to be on time to wire that instead. See how you can lose a whole year’s development while you think you’re just growing a healthier tree? And the wires that cut in can create bark and branch damage that may have to be cut off, too. So go get that wire and get busy, tiger.
Turn your pots every week. Garage sales frequently have cheap lazy susans to make this easy. Check your trees at night sometimes, when things look all different by flashlight and you may find night pests like earwigs and slugs that you didn’t know you needed to deal with. Sears sells a Craftsman lighted hat to make this easier. Put sphagnum moss on the tops of pots out in full sun to keep surface roots alive and healthy. New Zealand sphagnum is thought to be the cleanest and best, with nice long fibers. Some garden centers like the one behind the United Market on East Second street carry this in bricks of different sizes, which will make this easier, and there’s a friendly, knowledgeable woman who works there who is very helpful. Some low-nitrogen fertilizer at the beginning of September can be a great thing for a tree that lacks vigor, needs to just get bigger quicker, or will be trying to set next year’s fruit and flower buds this Fall. Ewing’s, on Irwin Street, San Rafael sells big old bags of Grow Power 5-3-1 and some organics that can make this easier. You can get disposable woven paper tea bags at most Asian markets which will hold three tablespoons of fertilizer. Placed around a tree on the soil and watered, they will leach a small amount of fertilizer into the soil daily, and that will make this job easier.
Make sure there’s peace in the garden and peace in your life as often as possible. A lawn chair, a cool drink and some silent reflection can make this easier. Try to locate love and joy in your heart as often as possible. They seem to reside in close proximity to one another. A joyous love relationship with another human being can awaken your heart and help to make this easier. Extend this joy to your friends, your dog, your garden, maybe even the cat, and your life will begin to mean more. To feel joy is to become stronger and more youthful and more open to whatever’s next.
– The Taskmaster