Ask the Gardener: What is wrong with my peonies?

Ask the Expert Gardening
Peonies are pictured in Marseille, southern France, on April 25, 2018.
Peonies are pictured in Marseille, southern France, on April 25, 2018. AFP Photo / Boris Horvat

What to do in the garden: Now that the threat of frost is past, this is the week to buy tender summer plants while the selection is greatest. So visit your local nursery without delay. Plant summer bulbs such as dahlias, begonias, and gladioli as well as annual flowers, especially those refreshingly inexpensive “starts’’ growing in tiny six-packs. If you have hungry critters, plant yucky tasting impatiens, marigolds, nicotianas, snapdragons, and zinnias. But remember that annuals require more frequent summer watering than perennials, so practice some restraint. You can buy preplanted flowering containers anytime throughout the season, but you will get the largest selection now. Transplant hot-weather vegetables such as tomatoes, peppers, melons, squashes, cucumbers, and eggplants. If seedlings get decapitated by cutworms, push an aluminum protective collar into the ground around each stem and feel around a couple of inches under the soil nearby for a curled-up grub to squash.

Q: What is troubling my tired old peonies? . . . Half produced one or two buds this year . . . They always bloomed profusely, and nothing in their environment changed between this spring and last.

M.S., Chelmsford

A: When peonies open they look like they’re wearing Victorian fancy dress. People plan their vacations around the brief June appearance of these garden party belles. Easy, longlived, and untroubled by cold winters, they can be grown by any New Englander with a sunny spot. So what could go wrong? Well, mulching can reduce blooming, as root crowns need to be positioned just under the soil surface. Check for stems blackened by bortrytis blight. If your peonies have blight or too much shade, move them to a sunnier spot where water does not collect. Add new soil amended with peat moss to improve drainage. Take the opportunity to space them a least three feet apart for better air circulation. Scatter bone meal around crowns in late August, the ideal time to transplant. Thin any branches or shrubs that cast shade, if possible. Last August, I moved a half-dozen peonies growing under increasing shade to a full-sun location, and they have more flowers now. Stake peonies with metal hoops, and pinch off side buds for larger flowers. Don’t worry about ants on the buds; they are harmless. Remove every bit of stem and leaf to the garbage when you cut them down in the fall to get rid of any botrytis spores.

Q: My husband and I debate whether to cut down a messy oak that drops leaves and acorns on our roof. What would be a fast-growing and attractive specimen tree to replace it with?

C.J., Cohasset

A: Stop! You’re torturing me. I hate it when developers or homeowners cut down mature oaks for convenience. Since the extinction of the foundational American chestnut tree, the 12 species of native oaks have become the crucial ecological glue that holds our woodland communities together, providing the most food for birds and other wildlife. With the onrush of climate change, these slow-growing trees may never be able to replace themselves. So think of that oak as a sacred tree, like a sequoia with acorns, and leave it alone.

To learn more, sign up for “The American Oak: Diversity, Ecology and Identification,’’ a one-day workshop with noted oak expert and Polly Hill Arboretum director Tim Boland, on June 9, from 9:30 a.m. to 1 p.m. at Jennison Hall at Bentley University, 175 Forest St., Waltham. Registration is $52 through Grow Native Massachusetts at

Events: It’s garden party time! The Massachusetts Horticultural Society’s annual garden party benefit, “A Night in Napa,’’ is June 14, 6-8 p.m., at Elm Bank, 900 Washington St., Wellesley. Reserved tickets are $100 at or 617-933-4945. Dogwood Days at the Wakefield Estate, Brush Hill Road, Milton, includes a Garden Conservancy Open Day, June 9, 10 a.m. to 4 p.m., which features a fund-raising tour of my own Milton garden ($7 per garden). The estate’s annual garden party will be June 16 at 5 p.m.. Reserved tickets are $75 at, or call 617-333-0924.


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