An early gardening mentor of mine once assured me, “If you can get through weed season, you’ll be okay.” By weed season he meant spring, the time when weed seeds, encouraged by the wonderful soil preparation you’ve given your garden, germinate happily in all that bare ground. At that time it’s paramount that you cultivate the soil frequently to keep intruders from getting ahead of your young seedlings. Kept weed-free, vegetable plants will soon gain the advantage and shade many of the weeds out. That’s what my adviser meant about getting through.

I’ve come to realize, though, that there are really three weed seasons, of which spring is only the first. The warm summer weather rewards warm-season weeds such as purslane and pigweed, just as it rewards peppers and tomatoes. Growth is rapid, and if your back is turned for a week, the purslane becomes a creeping carpet, the pigweed a forest. When crops grow large, weeds will be fewer but stronger. That’s why cultivation mustn’t stop.

I think the hardest but most important lesson to learn in gardening is continuous cultivation. Just going though with a hoe and shallowly messing up the soil a little, every day or so, will keep it weed-free, because tiny weeds never have a chance to grow. The job takes so little effort, so little time and so little skill, and yet it rarely becomes habitual. Why focus on nearly invisible green specks in the bean and tomato rows when the beans need picking and the tomatoes need pruning? Why indeed?

The third weed season is late summer and fall. As the weather cools, many of the weeds are smaller. Some of the crops are spent and have either been pulled from the ground or just left in place. Maybe you’re in the kitchen a lot, stocking the pantry with jars of pickles and jam. In any case, it’s the season of the big shrug. Even if you’re good about planting fall crops, the garden has lost some of its glamour, and a few little weeds here and there no longer evoke much shame.

Beware those little weeds. This Saturday marks the autumnal equinox, when the days and nights are the same length, halfway between the longest day of summer and the shortest day of winter. What shorter days do to many warm-season plants is to make them grow less but bloom at a smaller size. Though the weeds might look a little more harmless now, they are feeling the seasonal prod and leaving behind a parting gift of seed.

Pigweed in bloom. (Barbara Damrosch)

The other day I was looking closely at the suckers on my tomato plants, those long fruiting branches that arise from the fork between an established branch and the main stem. There was scarcely a sucker more than an inch or two long that did not have at least one tiny flower already. “Quick,” they seemed to say. “Breed.”

It’s not time to put away the hoe yet. But soon it will be winter gardening season, a time of cold frames, greenhouses and cool-weather crops that don’t set seed until the days grow long. And very few weeds.

Damrosch is a freelance writer and author of “The Garden Primer.”

Tip of the week

For an instant fall salad garden, fill a 14-inch pot with potting soil and sprinkle seeds of loose leaf lettuce or a mesclun mix. Thin out the seedlings as they emerge. Thin again as needed to space young plants about three inches apart. To harvest through November, snip leaves with scissors, which will allow new leaves to grow. Keep the soil moist but well drained.

— Adrian Higgins