Bonsai Care in the Time of Drought

By Gordon Deeg and Jerry Carpenter, Summer 2014

Living in the West we all worry about years of drought. The summer of 2014 is going to be hard on many bonsai enthusiasts living in California and the Southwest US. Water rationing in the state will raise water prices and curb water usage to the point that we will need to concern ourselves with severe water conservation.

I have asked a few people around the Bay Area how they coped with this issue in the past. Some indicated that they added more fir bark, Perlite, or other soil amendments to plants to retain water. Those options have side effects on the health of the trees and may lead to higher rates of disease. Changing soil mixtures may be an option for those trees requiring repotting but is not necessarily an option for every tree in your collection.

Here are some of the ideas we would like to share with club members and hobbyists in the area for this summer:

  • Move your trees out of the harsh sun as it can evaporate water very fast and may require you to water more than once a day. Shade means cooler pots and soil and less evaporation. Shade cloth is highly recommended. Remember that putting our trees under yard trees raises the risk of pests so you’ll need to inspect them more often.

  • Cover your bonsai with insulating material (outside of the pot). Using towels between pots could retain moisture and cool down the pots longer. These will have to be changed periodically. There are also mats that can retain moisture for the benches and keep that area cooler.

  • We can also cover the soil with sphagnum moss to retain moisture and protect those surface roots from drying out. This means you will have to adjust the amount of water or the frequency of watering if the moss stays wet.

  • Adding Perlite or organic material to a potting mixture is an option for trees or containers that tend to dry out faster. Remember this can only be done on trees being repotted now. After the trees get established you will want to watch for fungus if the material stays too wet.

  • Placing trees closer to the ground will keep them cooler. Many of us have high pedestal stands that results in better air flow but it also means the trees will dry out faster. If you move them to the ground, be sure not to place them where critters and slugs can feast. You will want to keep them away from the ground itself. There are many things that can be done to keep the bad things away so be sure you know your area. I put trees near the ground out of the sun on those hand mobile planter systems with wheels but I have to check for slugs and spray for pests more often.

  • Hose watering or hand watering trees this summer may be your best option: albeit more labor intensive. If you use a hose be sure to use a fine sprinkler with a turn-off switch or pressure release to save water as you move from tree to tree. The worst option would be an open hose end because you cannot control the amount of water and will waste considerably more water.

  • Gordon suggests capturing clean water that you don't use. Think of things like the water wasted as you are waiting for the hot water when taking a shower. Be conscious of run-off water everywhere.

  • Spraying some species of trees with Cloud Cover or Anti-stress 2000 when the temperatures are high can be helpful in reducing the transpiration reate. Basically the latex covering will allow oxygen and carbon dioxide to pass through but not water. If you use these products you will need to spray again about every two weeks. 

  • Water capture will be very important. We suggest placing one or more large concrete mixing tubs under pots or benches to capture runoff water that can then be reused in hand watering. (available at Home Depot, Lowes, OSH for about $12) You can water your bonsai with this or yard plants.

  • Automatic sprinkler systems can waste a great deal of water. It is important to water trees until water flows out of the bottom of the pot but unattended watering systems cannot shut down once this happens. So, they usually run too long and waste water. Monitor sprinkler systems carefully and consider shortening the timer interval or capture as much water as possible for reuse later.

  • Keep a few large containers of captured water in bins around your garden. Be sure to use mosquito fish, water darkeners to limit algae orperhaps even cover them. These bins of water can be used as the water supply becomes more limited and opened to create a more humid environment for your trees.

  • The last suggestion is not one we want to think about but consider reducing the number of trees in your collection. Many of us have trees that are substandard and may require more care and resources then we can give. If your collection is very large the water bills can get very expensive. Consider giving unwanted or marginal trees to the BGLM who can then sell them at a future Mammoth Fundraiser or sell them at your next club event.

All of these are just ideas on surviving the drought. You may have some creative methods we should know about and I encourage you to share them with clubs and friends who care for a collection of bonsai.