A GENERAL GUIDE TO SEED SOWING DATES: 4 WEEKS ??? Vegetables: Vine crops like melons, cucumbers, gourds and squash. (TIP: Use peat pots for vine crops as they do not like their roots disturbed once established.) 6 WEEKS ??? Vegetables: Tomatoes, head lettuce, and cole crops such as cabbage, brussels sprouts, cauliflower, broccoli.