UNITED STATES—From the time they get planted in early spring, tomato plants are expected to perform a bit better than they did earlier in the season. They start out with only a few early tomatoes, but quickly become prolific. Production continues to increase as the plants grow all through summer . . . until now. Newer leaves on top are not staying so far ahead of fading leaves below.
While the weather is still warm, it is difficult to say how tomato plants know that autumn will soon replace summer. They do not seem to be intelligent enough to realize that every day is imperceptibly shorter than the one before. Nor do they seem to be sensitive enough to notice if the nights get slightly cooler. They just know, and they tell all their friends.
If zucchini plants have not started to fade and sag, they will soon. As weather cools, they no longer grow faster than the mildew that they tolerated all summer. Any fruits that are present now should have time to finish developing, but there probably will not be many more after that. (Zucchini fruits are eaten before mature anyway.) Other warm season vegetables are in a similar state.
Acorn, Hubbard, butternut and other winter squash grow through summer just like summer squash do, but are not harvested until the vines wither in autumn and winter. Unlike summer squash that continue to produce many tender juvenile fruit to replace what gets harvested through summer, winter squash plants put all their effort into one or two large ripe fruit.
Warm season vegetable plants still need to be watered as the foliage slowly deteriorates. They only begin to need less water as they lose foliage and the weather gets cooler. They may like to be fertilized one last time, but will not not need it again. Any last phases of corn will stay thirsty later than other vegetable plants because they deteriorate slower, and are rather thirsty anyway.
Seed for broccoli, cauliflower, cabbage, kale and certain other cool season vegetables can be sown in flats or cell packs now so that their seedlings are ready to go when the warm season vegetables relinquish their space in the garden. If space allows, seed for beet, turnip and turnip greens can be sown directly into the garden. Carrot seed should still wait for cooler weather.
Highlight: autumn sage
Perhaps in the wild, it blooms in autumn. Where it gets watered in home gardens, even if watered only occasionally, autumn sage, Salvia greggii, blooms all through summer as well. If pruned back severely over winter, it starts to bloom even sooner in spring. The tiny flowers are red, rose, pink, peach, very pale yellow, lavender or white. Some poplar cultivars have bi-colored flowers.
Compact autumn sage that does not get much more than a foot tall is uncommon. Larger cultivars get four feet tall and broad, with more open growth. Most get about three feet high and a bit wider. Without severe winter pruning, stems can eventually get twiggy, with sparse foliage on the exterior. The tiny aromatic leaves are less than an inch long, and visually resemble oregano.
Even though it is not native to California, autumn sage is popular for native landscaping because it does not need much water. Just like native sages, it attracts butterflies and hummingbirds.