Spring plant sales for nonprofit groups have become a lot more complicated. For that reason, fewer groups hold them than used to.

One of the biggest of the remaining sales is run by the Cumberland County Master Gardeners at Tidewater Farm in Falmouth. It will be held this Saturday.

“We have kind of transitioned to posting our plant sale on Saturday of the Memorial Day weekend because that is the earliest time to plant your tender summer crops,” Pamela Hargest, a University of Maine Extension horticulturist at Tidewater who coordinates the sale, said in a telephone interview.

The Cape Elizabeth Garden Club, of which I am a member, stopped having its annual sale because of pests like the winter moth, which can be spread when plants dug up for sale in an infested area are purchased at a sale, driven to other areas and replanted. Some experts have speculated that the winter moth arrived in coastal Maine on garden plants that residents of Massachusetts had dug up from gardens there and transported to their vacation homes in Maine. But the winter moth, Hargest noted, is just one of several pests – she cited the jumping worm as another – that humans can inadvertently transport. To avoid contributing to the spread of invasive pests, the Master Gardener sale will offer no plants for sale that were dug in places where the Amynthas jumping worm is known to exist.

Also, volunteers rinse the soil from the roots of all perennials dug up from local gardens and repot them for the sale in a peat-free mix. While it’s a lot of work, it is the only way to ensure the sale doesn’t unintentionally spread dangerous pests, Hargest said. Because removing the soil from trees and shrubs is even more work, the Master Gardeners sale does does not offer newly dug trees and shrubs.

Proceeds from the sale are the major source of funding for Tidewater Farm. And if you go, be sure to allow time to tour the garden there.

Many other plant sales are occurring across the state, but some organizers are less careful about invasive pests than the Extension, so let me offer one piece of advice for buyers: If the sale is being held by your hometown garden club, it’s probably OK, because if your neighbors have winter moth, you probably do, too. But if the sale is 20 miles or more from your home, pests could be a problem.

Bearing in mind my warning, here are a few other plant sales in the weeks ahead:

Camden Garden Club Plant Sale, 11 a.m. Thursday, St. Thomas’ Episcopal Church, 33 Chestnut St.
Belfast Garden Club Plant Sale, 10 a.m. Saturday, Steamboat Landing and Belfast Boathouse.
Alan Day Community Garden Organic Seedling Sale, 10 a.m., Saturday, 26 Whitman St., Norway.
Bake, Blooms, Books and Bargains, 10 a.m., May 29, Arts Center, 8 Hancock Ave., Hiram.
Central Maine Garden Club Plant Sale, 8 a.m. June 3, Oakland United Methodist Church, 20 West School St.
Brewer Garden & Bird Club Annual Plant Sale, 8:30 a.m., June 10, Brewer Historical Society, 199 Wilson St.
Friends of the Rockland Public Library Annual Book & Plant Sale, 9 a.m. to general public, June 10, Rockland Public Library, 80 Union St. 

Tom Atwell is a freelance writer gardening in Cape Elizabeth. He can be contacted at: tomatwell@me.com.