Saturday, July 13, 2002
Submitted by Calvin Finch, Ph.D., Manager, Conservation Division, Water Resources & Conservation Department, SAWS, and Horticulturist

SOGGY ROOTS

Last week I was discussing ways to care for your plants in a drought. This week, after nearly 20 inches of rain, we are facing plant damage due to excessive water. The symptoms are really very similar because the mechanism is the same. When there is no water available in the soil, the plant cannot pump water and nutrients to the leaves, fruit, or flowers. Ironically, the same thing happens when the soil is soggy over a period of days. Drowned roots lose the ability to bring in water and nutrients to the leaves, and fruit and flowers are starved just like in a drought situation. Fruit and flowers are dropped, leaves yellow and defoliate, and the roots rot.

In less severe situations the problems you will see are tomato fruit cracking, flowers aborting, and leaves showing tip burn. Established plants with a well-developed root system may suffer some symptoms including root damage, but most of the plant functions will continue. When things dry out, the roots will repair themselves.

Among the things you can do to help prevent excessive rain damage is to remove the driphole saucers from container plants. If you recently planted a tree or shrub, dig down along the root ball to insure that the planting hole is not acting like a well. If water is pooling in the planting hole, just leave the new area you just dug near the root ball open for a few weeks to help drain the planting hole. Another option is to pull the plant out of the hole and put it back in the container until things dry out. 

If you have mulched deeply around plants, take the time to remove any mulch against the trunk or stems of the plants. Tree bark is designed to protect the inner workings from dry air, not soggy mulch. It is susceptible to rotting if it cannot dry out because it is buried in wet mulch or wet soil for more than four or five days at a time.

Mulch over the roots is not usually a problem unless the plant is especially sensitive to root rot. Iris is the most obvious example.

Nine or ten days after a spell of wet weather, everything will dry out again. Be aware that plants with injured root systems will require watering more frequently than they did before the damage occurred. They will be trying to support themselves with a reduced root system. Dig into the soil one-inch with your finger. When it dries that deep, it is time to water again. It is essential to let the soil dry to one inch between waterings, but not to wait too long.

Containers have a limited reservoir. One-inch or 25-inches of rain is all the same to them. Once the soil reservoir is full, extra water is wasted. Two or three days after the sunny 95-degree F. days resume, the container will require watering.

Despite all the rain, drought restrictions continue for at least 30 days after they are declared. Although with our situation (refilled aquifer) now, it would be reasonable to end restrictions; in a normal situation, the 30-day rule is reasonable. The restrictions are designed to reduce pumping and contribute to an increase in the aquifer level. If you left restrictions every time the aquifer moved above 650 ft., it could be like a yo-yo. Reduced pumping resulted in an increased aquifer, and restrictions were removed, which resulted in increased pumping, and another drop in the aquifer level, which then required us to declare restrictions again. It is better to stay in restrictions until we are sure the dry times are over.

The good news is that with all the rain a once per week lawn watering for two weeks will not be a problem.

Those of you who want to comment on low-flow toilet performance, please complete the survey on www.saws.org. Click on Conservation and then Low-Flow Toilet Survey.