Ask the Gardener: So you think your perennials are dead. Here’s how to know for sure.
This week you should start pulling weeds before they go to seed.
What to do this week: Start pulling weeds when they flower so you can identify them but before they go to seed. The worst is probably Eurasian garlic mustard (Alliaria petiolata), whose small flowers, each with four bright-white petals, are clustered atop super straight vertical stalks lined with triangular, pointed leaves. Remember the proverb: “One year’s seeding means seven years’ weeding.’’ Do not compost garlic mustard.
Q. Are perennial stalks from last year alive or dead? Should I cut them down now?
CINDY BARAN, Canton
A. The definition of a perennial is a plant whose top dies over the winter, but whose roots survive underground. Those roots are producing new shoots now, so you want to cut off immediately any dead stems still attached to the plant from last year to make room. All the old stalks of true perennials will be dead, so just prune them level with the tops of these year’s emerging greenery, trying not to nick the new shoots. You are, sorry to say, in a race against time. But remember that trees and shrubs usually lose their leaves in the fall, but most of the stems remain alive and sprout new leaves in spring.
If you are unsure whether you are dealing with a true perennial or a small shrub that looks like a perennial, cut off a stem and look in the center for traces of green, the sign of life. Some woody shrubs, such as roses, will contain both living and dead stems. Cut back gray dead-looking stems to where the green begins to take hold, and prune just above any sign of a leaf bud developing.
Q. I have milkweed beetles that can defoliate a plant in two days. I pick them off each night and drop them in a glass of beer. I’m afraid of pesticides but wonder whether there is an easier way to get rid of them.
JANET SIGREN, West Bridgewater
A. Congratulations on growing native milkweeds, which host threatened monarch butterflies. I grow three kinds, common milkweed (Asclepias syriaca), pink milkweed (A. incarnata), and stunning orange butterfly weed (A. tuberosa), my husband’s favorite flower. I’ve seen milkweed bugs only on my prolific self-seeding common milkweed, and I actually like the way these bright orange-and-black bugs contrast with the colors of the pods and their silken parachutes. I even bought an art print of this image, and I include these bugs on my garden tour as a scenic feature. I don’t find them very destructive, and I don’t get overrun, perhaps because the birds eat them.
Maybe another pest is devouring your milkweed, such as Aphis nerii, a tiny golden aphid. You will definitely have fewer milkweed bugs if each fall you clean up spent stalks, pods, and leaves where these insects overwinter. Hand picking is good. Spraying insecticidal soap so it covers each plant is a more aggressive approach but should be safe if you follow label directions. Definitely don’t spray with pesticides, because they may hurt the many butterflies and birds that milkweed attracts, which is like inviting guests to dinner and then serving them arsenic. You have created and are managing a little ecosystem here, and it includes bugs, the great majority of which are harmless and essential food for birds, most of which cannot reproduce on a diet of birdseed alone.
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