Tips for home gardeners, from Arboretum veterans:

• First step: "A soil test is all-important" to check nutrient levels and needs, said extension horticulturalist Mary Meyer.

• Timing is everything. Apply mulch too soon, groundsman Ted Pew said, and you'll delay the warming up of the soil. Too late, horticulture manager Tom Brinda added, and the weeds will have germinated. Individual conditions vary, but as a rule of thumb, apply mulch by mid-June.

• Don't use too much mulch around trees ("you don't want the trunk buried," Brinda said). Or perennials ("too much moisture on the crown on the perennial can rot it in a rainy summer or in winter melting.")

• "Always know your source material," said Pew. "You don't want grass clippings from where they just put 2,4-D or pre-emergent [herbicide]."

• Look for these words: "Double-shredded hardwood," especially the hardwood part. The Mulch Store, Home Depot, Lowe's, Mills Fleet Farm and Hedberg Landscape & Masonry Supplies should have it on hand.

• Consider buying mulch by the yard. Either rent a truck or have it delivered.

• At certain times, said Brinda, "you can flag down any arborist and get them to dump wood chips into your yard for free."

• Make your own mulch: Rake leaves 6 inches high in the fall, Meyer said. The next spring "go down a few inches and get these wonderful chunks of decomposed leaves, and use them."