The vegetable I'm most likely to forget to plant each year is garlic (stinking rose).   Although it's planted at the end of the season along with lettuce, endive and radish, garlic isn't harvested with those other vegetables, which ripen in the cool moistness of autumn. Garlic ripens almost a year hence, in the heat of summer.

Nonetheless, now is the time to plant it.

True, many gardeners plant garlic in early spring and still reap decent crops. Gardening books and magazine articles, however, direct you to plant now. Let's examine the logic: Garlic rarely makes seed, so it is grown by planting individual cloves, which together make up a bulb or ''head.''

After being planted, the cloves first grow leaves and roots and then, in response to the long days and warm temperatures of summer, heads. New leaves cease to develop once heads start forming; the more leaves the plant has pumped out before this occurs, the larger the heads.

What we all want from our garlic is big heads. So although you can reap a garlic crop from spring-planted cloves, or a larger one from fall-planted bulbs, late-summer planting gives cloves the most time to grow the most leaves. This yields the largest heads. Leaves poke up through the ground in late summer, take a rest or even die back a little when temperatures plummet in winter, and resume growth in spring.

Late-summer planting also gives roots the most time to grope further into the soil before cold weather strikes. Not only is the plant then able to drink in more water and minerals, but it is ready to do so with the first warm breath of spring.

A large root system early in the season is a special advantage in years when summer weather turns bone dry. All those roots taking firm hold of the ground also prevent freezing and thawing of the soil in the months ahead from heaving the cloves up and out of the ground. (This is one reason that mulching is so heartily recommended after late-fall planting of garlic in the north.)

Ready availability of fresh cloves is one more plus for planting garlic in late summer. It's a lot easier to plant now than to store bulbs in perfect condition until spring for planting.

Garlic comes in many varieties 300 by one count so look and ask around for what might be good to plant. Select a sunny site with soil that is rich, well-drained and weed-free.

Don't snap cloves off the heads until you're ready to plant. When that time comes, select the largest and most blemish-free cloves and set them upright in planting holes.

Are there any disadvantages to planting garlic now? Only that it's hard to remember to do so.