The summer solstice is in the rearview mirror. Even though the hottest days are before us, the longest days have passed. If you haven’t planted your tomatoes or melons yet, you might not bother. The plants will grow like steroid abusers, but there isn’t time for the fruit to ripen. Or maybe you’ll get one small melon. Trust me, I’ve been there. But there is a silver lining to the inevitable cooling. This is the beginning of the fall gardening season. It’s your last chance to sow quick-growing, heat-tolerant plants, like peas, beans, and cucumbers, and time to start sowing your cold-loving crops, like lettuce, spinach, beets, broccoli, mustard, cabbage, collards, carrots, kale, and radishes, which can live well into winter. So if you’re willing to cover your greens with blankets and even build cold frames around them, you can coax a four-season harvest out of most planting zones. For …