Guided by soil temperature rather than the calendar or phase of
the moon, here is a bit of gardening advice for the month of
May. These ideas, plus many more, can be found in my upcoming
book, “The New England Gardener’s Year, a Month-by-Month Guide
for Maine, New Hampshire, Vermont, Massachusetts, Rhode Island,
Connecticut, and Upstate New York,” to be published later this
year by Cadent Publishing. Plant by soil temperature Soil
temperature is the most important factor in deciding when to
direct sow main-season crops and when to transplant seedlings.
Many of our summer vegetables are tropical in origin and will
not grow well until the soil has sufficiently warmed. Here are
some useful guidelines: Minimum soil temperatures at a 4-inch
depth for transplants: • 60 degrees: tomatoes, tomatillos,
cucumbers. • 70 degrees: peppers, squash (both summer and
winter). • 75 degrees: cantaloupe, sweet potatoes. Minimum soil
temperatures at a 2-inch depth for direct-sown vegetables: • 50
degrees: onions. • 50 degrees: be