On the last week of April... "Hardening Off Heiloom Tomatoes" on their 2nd Day of hardening off. You put the tomatoes out 7 days consecutively with the first day going out for one hour then brought back into the house. Each day you add an hour, so on the second day it stays out to harden for 2 hours and so on. On day 8 you place them in the greenhouse still in their milk jub containers but with the tops folded over so the plants continue to grow upward. The 1st of June is when you plant them in the greenhouse soil. Any earlier does not help the plant to grow any faster. Planting at the beginning of June is the best time as the weather is warmer and the plant will thrive in these conditions.