Timing, as always, is everything. Transplanting can continue through summer. Survey your site, keeping in mind that with a few exceptions, most mosses require shade, acid soil, and good moisture. Large, deciduous trees like oaks, maples, and beeches provide plenty of the cool, damp shade that mosses love. Birch, black cherry, and shagbark hickory are other good canopy trees.
Evergreen trees present a problem because the needles they drop tend to suffocate moss.
Soil is the next important consideration. Mosses generally prefer acidic soil with pH levels of 6.0, 5.5, or lower, in which New England is rich. Kits for testing pH levels are available at garden centers, but professional soil testing labs are preferable. Be sure to take samples from different parts of your yard to assure accurate readings. Mosses love to be kept moist, but too much moisture without any sunlight can cause mold.