The past few gardens have has a sad theme for the generator seed. This week it's the weekend of the solstice. If you live in the Northern Hemisphere you have the longest days, and lazy summer evenings. If you live in the better hemisphere, then you can look forward to the dark nights fleeing and spring returning. For plants the solstice might well be a useful signal. The photoperiod, the period when plants are exposed to light starts to reduce. Combining this with other signals, like...