Ask the Gardener: How to get rid of grubs for good

Ask the Expert Gardening
Associated Press/File

What to do this week: September turned into a second August, with high temperatures and scant rain, so water new plantings and all trees and shrubs through October, especially during weeks when less than an inch of rain falls. Finish lawn restoration in the next two weeks, keeping seeded areas constantly moist until the new grass sprouts.

Q. Can we do anything to prevent lawn grubs from coming back next year? We don’t want to rip out our front lawn, and we have grandkids, so we need to be mindful of chemicals.

K.D., Wakefield

A. White grubs are immature beetles less than an inch long, with white, squishy C-shaped bodies and little black heads. They are found an inch underground eating grass roots and creating brown spots in lawns. While chemical poisons don’t work for all four species of grubs, organic HB nematodes (Heterorhabditis bacteriophora) will if applied between mid-August and early September. It’s a little late now, but because it’s been warm, you could try it. Or wait until late April or May. Some synthetic fertilizers kill nematodes, however, so stick with an organic fertilizer like Plant-tone if you apply them. Organic lawns are more resistant to grub damage. Fall is the best time to hang a birdhouse designed for wrens (with an entrance exactly 1⅛-inch wide). Next spring you can watch them feeding their nestlings from the white grub buffet table.

Two flowering redbud trees. —Adobe Stock

Q. How close to the house can I plant a redbud tree?

J.S., Dorchester

A. The common eastern redbud grows 25 by 25 feet, but a dwarf selection called ‘Ace of Hearts’ grows only 12 by 12. ‘Ruby Falls’ also takes up less room because of its weeping habit. ‘Merlot’ spreads only 15 feet, and may be the best choice for climate change because of its heat and drought-tolerant Texas parentage. Almost all redbuds have tiny magenta flowers for three weeks in May, but I also like the white varieties such as ‘Alba.’ They look like wraparound lights on naked branches. Redbud leaves turn yellow in fall, and the magenta spring flower buds are edible in salads.

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