Slice root ball to cure circling roots

Q: Last week, I read your technique of removing potting soil and pruning the roots of a houseplant that’s root-bound. Is the same technique used for landscape azaleas? Weston Becker, Decatur

A: Yes. When you unpot a landscape shrub before planting, you’ll almost always find roots circling inside the pot. This will prevent the shrub from rapidly growing new roots as it establishes itself in that spot. Though it seems drastic, the easiest way to deal with this is to use a sharp knife to make two to four vertical slices in the sides of the root ball. When that’s done, remove the bottom 1 inch of roots entirely. Splay the four quarters slightly apart when planting. This encourages the roots to grow outward to look for water and fertilizer.

Q: We just bought a home. The PG hydrangeas were allowed to reach tree height while the property was not occupied. We have cut them back to a reasonable size. The branches we removed are 1 to 2 inches in diameter. We would like to burn the branches in our fire pit. We know that hydrangea leaves contain poison if ingested. Will the smoke from the wood be poison in the air? Linda Reynolds, email

A: Hydrangea buds, flowers and leaves all contain a chemical called amygdalin. It is broken down in several ways to produce a small amount of cyanide. If you’ve heard that raw almonds, apple seeds and peach pits are poisonous, it’s because they contain amygdalin. It is broken down in one’s stomach to make tiny amounts of poison. In theory, the heat from your fire pit should destroy the amygdalin in the hydrangea wood. However, I make a practice of never describing something as “safe” or that the smoke is not harmful. I recommend that you discard the wood.

Q: I’ve read your website advice about applying preemergent. You say apply in March when the soil temperature at 2 inches deep is 55 degrees and rising. Where we live, the soil at that depth is already above 55 degrees but I don’t know if we’re “rising.” I’m tempted to put preemergent on even though it’s late January! James Walsh, Johns Creek

A: Let’s change my advice to “apply preemergent when the soil temperature at 2 inches deep is 55 degrees for five days and no cold weather is forecast.” So even though the soil temperature may be 55 degrees some days in January, you should wait until your local weather person announces that the current warm weather will continue and it’s clear sailing, weather-wise, until spring.

Email Walter at georgiagardener@yahoo.com. Listen to his occasional garden comments on “Green and Growing with Ashley Frasca” Saturday mornings on 95.5 WSB. Visit his website, www.walterreeves.com, or join his Facebook Page at bit.ly/georgiagardener, for his latest tips.