Sow Fall Greens
Time to start some mesclun greens and leaf lettuce in bare spots in the garden for fall picking. Mix in some compost before seeding and give new seedlings a dose of liquid fish emulsion.
To help your tomato plants direct all their energy into growing the fruit that's already set, prune off some of the vines that contain flowers but no young fruit. Pinch off suckers growing from where the branches connect to the main stem ( the leaf axils). Keep moisture levels even to prevent blossom end rot. Renew mulch if necessary.
Sow Cover Crops
Build the nutrient levels and organic matter in garden beds by sowing cover crops like annual ryegrass or buckwheat into empty annual beds. They will grow until winter kills them and then can be incorporated into the soil in spring. Cut down buckwheat before it flowers so seeds don't become a problem.
Harvest Onions and Garlic
When the tops of most of your onions have bent over, bend over the rest and let them sit for another 10 days. Then harvest on a sunny day and leave the bulbs to dry in the sun for a few days. Then spread them in a warm, airy place out of the sun to cure for two to three weeks. Separate the young, soft, and thick-necked bulbs and use them first because they won't store well. Place the rest into mesh bags and store in a cool, dry location.
Late summer is a good time to divide German and Siberian iris, rudbeckia, echinacea, daylilies, and hostas. Don't make the divisions too small or you'll wait longer for blooms. Trim the foliage before replanting. Be sure to set iris rhizomes just barely below the soil surface to prevent rotting.