An interesting article by the Bonsai Society of San Francisco found by Eric.
We are looking at El Nino rain events this year. The events can come one right after the other with significant rain each time being very possible. A troublesome issue for us is our soils staying too wet for too long a period of time and nutrient being leached out of the soil. The obvious preventions are having your trees in well drained, quality bonsai soil and covering the plants or placing them under a roof of some sort. If cover or a roof is not an option, then tipping the pots during or after the rain event is always a winner, especially the shallow pots due to the perched water in the bottom of the pot. Even picking up the tree, putting your hand over the soil and tipping the pot over 45 degrees or so to let the water can run freely out and over the lip of the pot, works well. You can be surprised at times as to how much water can still come out of a previously tipped pot.
After a warm El Nino rain the air can be very humid and still. In the nursery business we controlled greenhouse humidity, and of course heat, with exhaust fans to promote drying and fresh air in the green house.
So what can I do at home to improve drying conditions?
First, place plants in the sun after the rain event.
Second, after a rain event the air can be very still. During an El Nino I remember very high humidity and on some days fog scattered around after it rained. If these conditions exist after a long and/or a heavy rain event, it will not allow for proper/timely drying of soil in containers or in the ground. Bad things can happen to the roots not to mention above ground diseases. Soil evaporation, plant respiration and plant transpiration are minimal under those conditions. In 1983 during an El Nino period of rain after rain, an old nursery "salt" told me to get a fan and and point it at the plants to create artificial air movement. I have used a fan now on many occasions when the conditions warrant it. Once a breeze comes up, I turn it off unless the plants are very wet. Be sure to remove the fan before the next rain event.
For fertilizing or soil applied products for disease control, try to use dry products and let the next rain storm get them into the ground. Sometimes one cannot wait for the next rain so foliar feeding and foliarly applied disease products work nicely. For plants in the ground, the same applies when the soils are too saturated for soil drenches. My garden soil can literally back up with water after frequent, heavy rains, so foliar feeding kept my citrus alive and well until the roots recovered from the "drowning".
Hope this is helpful.
Shohin Study Group
SDBC member Charlie Mosse lets you know of interesting bonsai posts from around the web but especially shohin topics as he is leading the shohin group.