Cool-down lets plants store energy

By Walter Reeves

For the AJC

Q: I have an office cohort who says I should turn the lights off so the plants can respire. I’ve left them on and the plants seem to grow quite well. Should I indeed turn the lights off when I leave? Tim Love, Cumming

A: Plants respire 24 hours a day, using up sugars made by photosynthesis. You don’t need to turn the lights off to allow respiration. The problem comes when a plant grows in constantly warm temperatures. It doesn’t cool down and thus uses up just as much sugar as it makes. It’s best to drop the office temperature at night (I’m sure this happens where you work) to allow some of the food made during the day to be stored and used for future growth.

Q: What is the best way to purify soil to remove any diseases from it.  Would adding bleach work? June Schefker

A: Sterilizing soil is impossible in a practical sense. Even if you removed disease organisms from the soil it would quickly become contaminated again. It’s easier to concentrate on keeping plants strong so they don’t fall prey to disease. Giving a plant the appropriate amount of sun, water, fertilizer and drainage gives it most of the resources it needs to fend off, or easily recover from, pests. In my experience, making sure your clay soil drains properly, accomplished by the addition of organic matter, is the best way the keep plants healthy.

Q: I recently had two trees cut down because their roots passed beneath my sidewalk. The stumps and roots remain. I’m concerned that the roots will continue to grow. How can I kill them? Dick Pbrows

A: Some trees, like oak and pine, rarely send up root sprouts after the main trunk is cut down. Others, like sweetgum and ‘Bradford’ pear, sprout for years. Keep your eyes peeled this spring. If there are no green sprouts from the stump or the area around it, the roots are dead.

They will slowly deteriorate over the next few years and your sidewalk will be safe. If sprouts do appear, be persistent about clipping them at the soil line. With no leaves to make food, the roots will eventually die.

Q: I recently read about Poet’s laurel. Can you grow it in Atlanta successfully? The area of our yard I was thinking of gets full sun about 90% of the day. Pam Aiken, Snellville

A: Poet’s laurel, (Danae racemosa), is a slow-growing evergreen shrub that sports bright red berries each winter. I've had a couple of plants in my woodland garden for four years and they seem to be happy.  One of the features of this plant is its great tolerance for shade. In the sunny spot you describe the leaves will quickly scorch. Look for a darker spot and the plant will thrive.

Listen to Walter Reeves Saturday mornings on NewsTalk 750 WSB-AM from 6 to 10. Visit his Web site, www.walterreeves.com, for detailed advice on Georgia gardening.