Mum's the word at Brookside Gardens in Wheaton. I went to the chrysanthemum display there last week. Much of the exhibition is done as topiary in the form of larger-than-human-scale insects. A flowering dragonfly, ladybug, praying mantis, inchworm and others, 20 in all, are swarming the conservatory. But don't worry: These colorful insects are well trained and will be there until Thanksgiving.

These ancient Chinese flowers have been planted in Asia for 2,600 years. The chrysanthemum has been the national flower of Japan for centuries. Mums are no less popular in this country, and yet we've known the hardy Korean Hybrids, the ones we plant in our gardens, only since they were introduced in 1933.

There are hundreds of varieties of hardy mums to choose from, and virtually all of them are grouped under one species, Dendranthema x morifolium. They are bred for color, type of bloom and size of flowers.

The hardy, or garden, chrysanthemums as these members of the daisy family are known, flower in the late summer or fall. They're available in every color but blue, and because they bloom in autumn, mums complement the red, orange and gold leaves that rain down around them.

While reflecting on the long ancestry of mums, I realized that we don't understand their culture very well in this country. This is probably because we classically install them as annuals. To use them as annuals, the guidelines are simple. Keep them moist. Enjoy their flowering. When they fade, put them in the compost pile.

To grow hardy mums as perennials, cut the plants back to four inches high when the blooms fade. This is when the temperature drops to about 25 degrees Fahrenheit, usually in late November. Mulch with about three inches of leaves, compost or aged shredded hardwood bark. If you don't know whether the mums you have are hardy, there's one way to find out. Plant them 18 to 24 inches apart and see what happens next spring.

Mums like full sun, eight hours or more, and are happiest with an eastern exposure. Although they are somewhat drought tolerant, you should water them deeply once or twice a week if there is a dry spell.

It's what you start doing in spring that makes a showy mum. This is also the best time to plant them. But unless you or a neighbor already have mum stock growing, now is the only time you can get them at most garden centers. Hardy mums are offered only when they're at their showiest, because that's when they sell. Because most mums get planted in the fall, and won't establish many new roots by winter, you may lose a few plants to freezing. But there will still be enough for you to nurture.

Proper periodic attention begins with an application of balanced low-nitrogen fertilizer to encourage flower production. Any general-purpose dry fertilizer at your garden center with an analysis of 10-10-10, 5-10-5 or 5-10-10 showing on the bag is fine. Sprinkle about two pounds per 100 square feet when growth begins. You can fertilize again in May and June as long as you "water in" the fertilizer. Stop when the buds form in July. You can use a spray fertilizer of 15-30-15 or 20-20-20, and follow all the label guidelines.

Even with sun and fertilizer, the key element for plant fullness is pruning, or pinching, as it's most commonly called. When mums reach six inches in height in spring, using your thumbnail and forefinger, or scissors, pinch or cut off the top two inches of growth on each shoot. Pinch an inch when when the plant grows another four to six inches. Continue pinching after each four to six inches of growth until flower buds begin to form in July. Then, when they come into bloom, they'll be shrubby, loaded with flowers and won't need staking.

One more maintenance suggestion: Divide your mums every two years. New roots and stems grow to the outside of the plant. In spring when the new growth is one to two inches tall, dig up the clump and tear or cut strongly rooted pieces from the edge of the old plant that have several young stems attached. The inside woody clump has lost ornamental value and should be composted.

Now that you know what is involved with mums' culture, perhaps you've resolved to treat them as annuals. It would be a mistake not to try keeping them for a year or two. You'll get a tremendous feeling of accomplishment from several simple gardening practices, and you're stretching your landscaping budget. I have used mums successfully as focal points on huge commercial properties with little extra maintenance. Mums that I only planted for a grand opening filled the entrance bed with flowers for three years before we had to replace them. I designed an entrance drive lined with mums for an institution that gave a great deal of attention to its landscaping, and these thrived for five to six years using the practices outlined above.

There is still time to plant mums, as long as you spread mulch for protection until spring. Plant them with lots of compost and keep them moist through autumn. And deer don't eat them, so they'll go the distance and come back to flower next year.

Mums can look like everything from marigolds to dahlias. They grow short, medium and tall, and forms are available that can cascade over walls and rocks or from window boxes. They are grouped by flower type into these categories: singles, anemones, doubles, pompons or cushions, quills, spoons and spiders.

I've offered names of several varieties. However, don't pick by name; simply choose a couple of colors and flower types, and try them. Three time-tested hardy mums in white are encore, illusion and Nicole. Yellow ones to try for dependability are goldmine and Jessica. Naomi, stardom and sundoro are pink. Russet-color mums are Sandy and triumph, and a couple of red varieties are bravo and remarkable.

There are far too many hybrids for you to stick to the varieties mentioned here. Strike out on your own and just start growing whatever you find that you like.

The Green Scene column last week should have said that soil temperatures must get down to 45 to 50 degrees Fahrenheit before spring-flowering bulbs can put down roots. Local soil temperatures are not yet cold enough, but it's all right to plant the bulbs now.

Lerner is president of Environmental Design in Capitol View Park, Md. His e-mail address is lernscap@erols.com