Gardening : Plant Zoning Contributes to Best Use of Water
Here’s a new word for your landscape vocabulary: zoning. As used in garden design it has to do with watering and what plants get to grow where.
The idea is simplicity itself: Only plant things with similar water requirements in the same area.
Garden designer Robert Cornell, who has done a number of drought-resistant gardens, is a big fan of zoning.
“You don’t plant a yucca next to a rose,” he said. “It’s that simple, but you’d be surprised how many intelligent people think that scattering a few drought-resistant plants through the landscape will make a difference.”
He calls that the “silver bullet approach”--”Buy a bunch of drought resistant plants, plant them here and there, and that solves everything.”
Zoning a garden designates certain areas to be watered a certain amount. For instance, decide that the far reaches of the garden are to be a drought-resistant, low-water zone. In that area plant only things that need very little water. Take out or move plants that might need more (chances are, however, that most shrubs and trees on the property line need very little water, even if they have been getting more). Nearer the house, you may decide that you want roses, azaleas or other plants that need more water, so that becomes a high-water use zone.
Cornell points out that those with automatic irrigation systems will have to make some changes. “You can’t water every part of the garden for 10 minutes every other day.”
A zoned garden needs a timer or clock that can irrigate at greater intervals--every 15 days, for instance, instead of every week. This allows you to have zones of infrequent irrigation. These new controllers are just becoming widely available. “Even better,” says Cornell, “is no electronic controller. You are the controller and irrigate only when it is necessary.”
If this sounds tricky, Cornell says it really isn’t. “There are always ‘indicator plants’ that show it is time to water.” They may wilt a little or the leaves may change color slightly, but it is a recognizable sign one can soon learn to see.
Cornell suggests that most landscapes can be divided into three zones. One for lawns, which require the most frequent watering, one for shrub and ground covers which require less, and one for the truly drought tolerant that may need irrigating only once a month.
Each should have its own irrigation system. Lawns could be irrigated with sprinklers controlled by a conventional clock. The shrub and ground cover area should be a separate zone. They could also be on a controller or clock, but drip would be a better irrigation system for these. The most drought-resistant zone should be manually controlled.
He also suggests putting trees on a separate system since they are deep rooted and need to be watered deeply but very infrequently. Drip systems are the best way to water trees because the water sinks in very slowly and does not run off.
Some accidental zoning may already exist in your garden. In Cornell’s own garden there was a section of the lawn that never looked good because the sprinklers really didn’t cover it thoroughly. Rather than try to water it properly, he simply changed the grass to more drought-tolerant plants that didn’t mind the dryish soil.
As for flowers, he suggests putting them in the zone that gets watered along with the lawn--if they are flowers that like lots of water--or plant them in the zone for shrubs and ground covers that gets less water, if they can get by on less.
