What to do this week Sow seeds of beets, chard, spinach, and lettuce now for a fall harvest. Pinch off spent flowers on annuals to keep new blooms coming. It is best if you can water plants in the early morning, slowly but deeply without wetting the leaves, which can encourage fungus growth. Good soil that has been amended with organic matter and mulched on top requires less frequent watering than bare ground. Container plantings need daily watering in hot weather because moisture evaporates on all sides. This is why hanging planters need the most frequent watering. Once the soil has dried hard, water may run down the edge of the planter without soaking in. If this happens, take the planter down and immerse it in a bucket of water until it is fully rehydrated.
Q. Every summer our annuals are inundated with slugs that quickly destroy the plants. I thought I had escaped this nuisance this year until last week when we had a couple of days of rain and high humidity. Insecticides don’t work. Any suggestions to keep these pests from destroying the beauty of our plants?
A. Most chemicals that work on slugs can also kill larger animals, so nonchemical tactics are better. The traditional organic method is to sink (empty!) tuna fish cans into the garden so the rims are just below the soil-top level. Then, believe it or not, you fill them with beer. The slugs apparently jump in, get drunk, and drown. Replace and repeat. There is no danger to other creatures, like slug-eating toads, which can apparently handle their liquor better. You can also create a physical barrier by sprinkling diatomaceous earth, which is made of fossilized algae. (But read the instructions, and don’t breathe it in.) The best but most expensive defense is to surround the problem area with 2-inch-wide strips of copper, which reacts electrochemically with slug slime. Slugs can’t get in. But those already inside can’t get out, either. So you’ll also need to put beer traps inside the garden fortress — or go out with a flashlight and salt shaker at night when slugs (and snails) are active. A sprinkle of salt is death-by-dehydration for slugs.
Q. I feel like I know you after reading you every Sunday in The Boston Globe. We have overgrown blueberry bushes in one of our beds. Can they be pruned?
A. Highbush blueberries can get pretty big, up to 10 feet tall. Prune them after they lose their brilliant red foliage in the fall so you can see their handsome zigzag branch structure. Don’t use hedge shears to trim the tips of branches. Instead, explore the interior of the bush. Cut branches that are too long back to where they attach to another branch. Prune the long branch off about half an inch from this crotch, so the cut can heal over with special cells. The plant’s energy will be redirected into the surviving branch.
Never leave a stump of more than an inch, or you invite infection. If the shrubs are crowded because they are less than 5 feet apart, consider cutting down every other one to allow the survivors elbow room. Most gardeners plant shrubs too close together when they are small, so such thinning is a common necessity. Digging up and moving crowded shrubs is backbreaking work unless the shrubs are quite small; the soil attached to the root ball can weigh more than 100 pounds. I prefer just to sacrifice the less vigorous ones.