Evan I would guess it takes the ground temps a bit longer to warm up in Mass. Once the leaves appear I top dress the bed with a bag of compost manure and keep them well watered but I really think they enjoy and thrive in our heat and humidity. I add osmocote14-14-14 four month in the spring in my beds and containers.
Too bad they are not winter hardy, huh.
we are trying to survive the japaneese beetles for two more weeks.
