- Im passing this along from Dona Inman. :Garden Assignment: Plant fruit trees all month, as well as arugula, asparagus crowns, broccoli & cabbage plants, peas, radishes, rhubarb & spinach. The 1st-15th, plant cauliflower plants, onion sets and seed potatoes. The 15th-30th plant beets seed, chad & sweet corn. Start sprouting sweet potato slips for planting in 6-7 weeks. Growing watermelons takes about 120 days from start to finish. So to have them by July 4, you need to plant them this week!!!