Watermelons, which require a long, hot growing season to reach maturity, present a challenge in the New England climate. The good news is that growing watermelons in Massachusetts is entirely possible, even with the state’s short summers and cooler nights. Success hinges on specific, proactive gardening techniques designed to maximize heat exposure and accelerate the plant’s development from seed to harvest. By selecting the correct variety and implementing season-extension methods, gardeners in USDA Hardiness Zones 5b through 7a can enjoy homegrown, vine-ripened fruit.
Overcoming the Short Massachusetts Growing Season
Massachusetts’s climate necessitates the use of season-extension techniques to mimic the long, hot conditions watermelons prefer. Soil temperature is more restrictive than air temperature, as watermelon seeds and transplants require a minimum of 70°F for optimal growth and nutrient uptake. Black plastic mulch is a highly effective tool to achieve this warmth, absorbing solar radiation and increasing the soil temperature by several degrees.
Laying down black plastic sheeting over the planting bed a few weeks before transplanting will pre-warm the soil, giving the young plants a head start. Using floating row covers or mini-hoop houses early in the season can also create a microclimate that traps warm air around the seedlings, protecting them from cold snaps and extending the growing window. These covers should be removed once flowering begins to allow for insect pollination. Planting outdoors should be delayed until approximately two weeks past the last expected frost date, when the soil has reliably reached the required temperature.
Selecting the Right Watermelon Variety and Starting Seeds
The first step toward success in a short-season climate is choosing a watermelon variety bred for quick maturation. Standard varieties may require 90 to 120 days to ripen, which is often longer than the reliable warm period in Massachusetts. Instead, gardeners should focus on “icebox” or short-season types that mature within 70 to 85 days.
Varieties like ‘Sugar Baby,’ known for its compact vines and 75-day maturity, or ‘Blacktail Mountain,’ developed for cooler climates, are excellent choices. Other fast-maturing options include ‘Golden Midget’ and ‘Yellow Petite,’ which can ripen in as little as 70 days. Starting seeds indoors is mandatory to bridge the gap between the last spring frost and the required days to harvest.
Seeds should be started indoors approximately three to four weeks before the planned outdoor planting date. Watermelons are highly sensitive to root disturbance, so using biodegradable containers, such as peat pots or coir pots, is essential to minimize transplant shock. Plant two to three seeds per pot, and once germinated, thin them to the strongest single seedling. This ensures the young plant focuses its energy on developing a strong root system before being moved outside.
Essential Care from Planting to Harvest
Once the seedlings are hardened off and planted outdoors in the warmed soil, consistent care is necessary for the development of sweet, full-sized fruit. Watermelons are heavy feeders, requiring a nutrient-rich start; aged compost or well-rotted manure should be incorporated into the planting area. Early in the growth cycle, the vines benefit from a fertilizer higher in nitrogen to support rapid vine and leaf expansion.
As the plants begin to flower and set fruit, the fertilization strategy should shift to a formula higher in phosphorus and potassium to support fruit development and sweetness. Consistent, deep watering is also necessary, especially during the period of fruit set and enlargement, as the fruit is over 90% water. Using soaker hoses or drip irrigation is recommended to deliver water directly to the root zone while keeping the foliage dry, which helps prevent fungal diseases.
Determining the exact moment of ripeness is important since watermelons are a non-climacteric fruit, meaning they will not get any sweeter after being picked. A reliable sign is the change in the color of the ground spot, the pale area where the melon rests, which shifts from pale white to a deep, creamy yellow color. The tendril closest to the fruit stem also provides a cue; when it dries and turns brown, it signals that the fruit is ready for harvest.