The lone voice of horticultural reason

Watering Wisdom

 6-11-1998 — We have had an entirely implausible spring for planting annuals; the final frost in my yard occurred April 12, a full month before the last possible frost date. Now that my flowering bulbs have quit their show and numerous perennials, such as Campanula, Ranunculus and Lysimachia are hitting bloom, my mixed beds are telling me where more annuals can be plugged in. Let’s all plant more of them this week (I’ve become a real sucker for annual salvia and, this is difficult to admit, zinnias) to provide those colorful foundations of constant bloom.

A neighbor asked yesterday how we were doing in terms of rainfall so far this season. My guess is we’re a bit behind; regardless, the lack of snowfall this winter didn’t give us much to start with, meaning the spring melt didn’t extend down one and two feet deep, where it matters most to trees and shrubs. Newly planted trees and shrubs (meaning those planted last fall up through now) should be watered once a week. Hopefully they were planted a few inches deeper than the surrounding ground level, leaving an indentation, so that a good five minute soaking with the hose for smaller shrubs and a ten or even twenty minute soaking for trees and shrubs over 5′ lets the water pool, then work slowly down throughout the root zone.

I’m finally getting around to planting some new flowerbeds I made last fall, and can assure you the soil has been quite dry so far. One nationally famous, very successful gardening guru still maintains that you can “wait until your plants tell you they’re thirsty,” meaning, water when they wilt. Of all the nonsense. You might get away with that with your impatiens (in fact, I get away with it with my impatiens all the time) but to let any perennial dry out to the point of wilting is devastating to the plant. Water your flower and vegetable gardens once a week in periods of no or only light rain; in fact, watering this sparingly during the hottest part of the summer works only if you water deep and have a good one- to two-inch layer of moisture-retentive mulch spread throughout the beds. On the other hand, don’t confuse a perennial’s wilting at 1:00 o’clock in the afternoon under direct, hot sun as a sign it needs water, particularly if you know you’ve watered recently. Most tall phloxes wilt midday in intense sun, as do Ligularia, Aster and Delphinium. It’s a defense mechanism-like fainting just before getting punched-and does not signal a plant needs water. Check your garden first thing in the morning or early evening. If plants are wilted, only then is it a clear sign you’ve been under-watering. Try not to let it happen again.

As it so happens, it has just started raining as I wrap this column up on Monday evening. It means nothing to me until I check my rain gauges when it’s over. An inch or more, I don’t have to water my perennials for at least a week. Half an inch is good enough for my annuals, and a quarter of an inch should keep that useless lawn of mine limping along until I locate the sprinkler.

The important thing to learn about rainfall is that anything less than a quarter of an inch doesn’t count.

Don Engebretson
The Renegade Gardener