Readers' Top 10 Gardening Mistakes

Mistake 4: Overwatering

"I kill everything. I never know when to water and when not to water. Help!"
Kelli Baker
New Philadelphia, Ohio

Garden Fix

Overwatering drowns plants roots, causing them to rot; underwatering, on the other hand, can dehydrate it. The no-more-guessing approach is to invest in an irrigation system with a "smart" controller, meaning that it automatically adjusts watering levels based on historical data and moisture sensors, says Rebecca Sweet, who designs gardens in the California bay area and writes the Gossip in the Garden blog. If you can’t afford a system, pay close attention to your soil. When the soil is rock hard, it needs watering. When you can grab a handful, squeeze it together, and form a loose ball, it’s just right. One trick: Plant a so-called indicator plant—one that wilts much more quickly than the others—such as a hydrangea or lettuce. "One look at them on a hot day will tell you whether or not you need to water your plants," says Sweet.