Tomatoes, potatoes, herbs and irises Blown cover:

1 Don’t allow soil to remain bare. After harvesting vegetable crops for the final time and removing the plants that produced them, don’t allow the soil they grew on — or any other soil in the garden, for that matter — to remain uncovered. Sun pounding on bare soil kills the beneficial microbial life living underneath. Aerobic bacteria such as actinomycetes, and mycorrhizae (symbiotic associations between fungi and roots), contribute mightily to soil fertility. But these organisms vanish where soil is bare. Where you see bare soil, deposit a layer of mulch several inches thick on the soil surface or plant a cover crop. Clover is a highly desirable cover crop because it not only adds nitrogen to the soil in the manner of all legumes (e.g., peas, beans and lupines), but its roots aerate the soil. After the clover matures and flowers, but before it goes to seed, incorporate it into the soil. Wait four weeks before planting another vegetable crop or any other garden annual or perennial favorites that strike your fancy. In California, fall is the best season for planting clover as a cover crop, so plan for it now. More than a dozen varieties of clover may be ordered at outsidepride. com.

2 Divide irises: If you divide and replant your flag or bearded irises now, you should see them bloom as early as next spring. The procedure is simple enough, especially since digging up irises is easy, owing to their shallow roots. Once they have been removed from the soil, their rhizomes, or thick semi-underground stems, can be pulled apart. You may wish to cut the leaves down to within several inches of the rhizomes for easier handling. Prepare your soil with a few shovels of compost and then lay the rhizomes down horizontally so they are half covered and half exposed. Three rhizomes planted together, with leaves facing outward, will make a nice cluster of blooms.

3 Preserve herbs: You can pick herbs continually, of course, but as summer comes to a close, the oils that give herbs their flavors and scents become most concentrated. To maximize taste and fragrance, cut leaves as soon as dew dries early in the morning, before temperatures rise. To preserve your herbs, run them under cold water, chop them up a bit and place leaf pieces in ice cube trays filled with water. Put trays in the freezer and extract your herbs, mummified in ice, as the need for them arises. It is also advisable to remove flowers from herb plants, since the seed-making process diminishes the potency of their foliage.

4 Dig this: Harvest potatoes and bulb onions when their leaves topple over after turning brown or yellow. Dig gingerly into the soil and carefully lift the tubers and the bulbs from the earth. Place them in the shade or in a garage with good air circulation to activate the curing process. After a week or two, the skin will have toughened, extending the storage life of these crops. Always keep potatoes out of the light to prevent them from turning green, which renders them inedible. You can grow potatoes and onions from store-bought produce, something to keep in mind if you decide to plant them next spring.

5 Looking ahead: Save tomato seeds for planting next year. This applies to openpollinated, heirloom varieties only, as opposed to hybrids, since only seeds of the former grow into plants true to type, meaning their fruit will be identical to that from which the seeds have been taken. Lay your tomato seeds on a paper towel and leave them there for two weeks. Fold up the towel and put it in an envelope, labeling it with the name of the variety and that day’s date. Stored at room temperature, tomato seeds remain viable for five years. Kept in airtight containers they remain viable twice as long. Among the most popular heirloom tomatoes are Cherokee Purple, Brandywine, Green Zebra and Hawaiian Pineapple. You will find tomato plants in the nursery through the fall and, once established in the garden, if the winter is mild, they may continue to produce fruit through the end of this year and beyond. Cherry tomatoes are especially notable when it comes the capacity for putting out flowers and fruit in the winter.