Gardening

Ask the Gardener: Is there a cure for beech leaf disease?

Plus, prepping your garden to prevent tomato blight next year and dealing with a hydrangea that just won’t bloom.

Beech trees with their fall color are shown on Oct. 20 in Marshfield, Vt. A disease that harms beech trees has been confirmed in Vermont for the first time in Vernon, in the southern part of the state. (AP Photo/Lisa Rathke)

By Carol Stocker

November 1, 2023

What to do this week This is my last garden column until next spring. Thank you, readers, for sharing your questions, experiences, and advice. The ground is still warm enough for planting hardy trees, shrubs, rose bushes, and perennials. This is also a good time for dividing and moving plants. I stick a few bulbs in these holes while I am rearranging the garden. Daffodils and alliums are excellent bulb choices because they are often long-lived, unpalatable to pests, and good in bouquets. Look for weeds threading through hedges while their contrasting autumn colors divulge their hiding place. Clip invasive vines such as bittersweet and porcelain berry that are climbing into trees and shrubs. Dip the cut end that is still attached to the ground into a bottle of Round-Up for a second or two to kill the roots. Unhook and drain garden hoses, and store fountains and lawn furniture. Buy a heated birdbath if you have an outdoor outlet. Support the use of electric leaf blowers instead of the very loud and polluting gasoline-powered ones. Collect leaves in a pile to become nutritious and weed-free leaf mold for mulch next year. Clean up debris in your vegetable garden to reduce plant diseases, but experiment with leaving some of your perennials standing until March to provide food and cover for birds.

Q. We have many beech trees on our property north of Boston, and most are showing signs of beech leaf disease. The foliage is dying off after the initial spring bloom. Are you aware of any treatment? We are fearful that our trees will die off.

K.F., Hamilton

A. Beech trees are suddenly and quickly dying throughout New England. The doomed trees include both the American beeches, which constitute a crucial 10 percent of our forests, and the charismatic European beeches, which command front yards with their spreading arms and silvery, smooth trunks. Chinese and Japanese beech trees are also infected but are resistant. Beech leaf disease is a fungus like Dutch elm disease, which enters the tree with the help of another organism, in this case a newly discovered microscopic nematode that lives in leaves. Identified in Plymouth County in 2020, it is now found throughout the state. There is no known cure, and infected trees die in three to 10 years.

Arborists don’t know how it spreads, but beeches in isolated locations have the best chance of being spared, said Scott Phillips, assistant manager of horticulture at Harvard’s Arnold Arboretum.

The unmistakable symptoms include striped leaves with leathery, crinkled undersides. Defoliation starts with the lower limbs. If you have a healthy-looking beech or one in the very early stages of infection, Phillips said, consult a certified arborist who can treat it with Broadform, which has been shown to reduce the fungal pathogen by 80 percent. It is currently in short supply, but Reliant is another fungal treatment Phillips recommended, along with PolyPhosphite 30, a fertilizer that can slow the disease. “You are trying to extend the life of infected trees, not cure them,” Phillips said.

If you don’t want to spend hundreds of dollars annually to add a few years to your beech trees’ lives, you are better off giving up now. The ultimate solution may be the future discovery of resistant individuals that are then cross-bred with Asian beeches. Meanwhile climate change coupled with increasing international trade may continue to extinguish many other tree species. Native American ash trees, hemlocks, butternuts, chestnuts, and elm trees have all faced extinction from imported pathogens, mostly introduced through trade with China.

Remembering the neglected unwatered trees I saw during the record drought of 2022, I would focus on watering, mulching, and fertilizing other tree species with a chance of longer term survival. Phillips suggested the American hornbeam as a native replacement for beech trees. “It has smooth bark and the same shape,” he said. Ultimately it doesn’t grow as big, but then how long will we be around to see it?

Q. My tomato patch with about 18 permanent stakes always has various blights that cause the leaves to die and drop off. While I always use bailed hay as a thick mulch layer, this year was worse than ever before. Significant rain may be one of the culprits. What should I do to give the tomato area a proper rest and get rid of as much of the blight spores as possible?

B.M.H., Littleton

A. You can try bagging all the garden refuse, but I think rotating the location of your tomato patch on a three-year cycle is more effective. Wipe your stakes and tools with isopropyl alcohol or ethanol to kill pathogens. No need to rinse it off.

Q. I have two small hydrangeas that were on my property when I moved here five years ago. I’ve tried everything but haven’t gotten a single flower.

M.S., Worcester

A. Give up! You got to know when to hold ‘em and know when to fold ‘em. Replace those old hydrangeas with a newer variety like Endless Summer that blooms more reliably in cold climates.