A Flower and Garden show will be held March 2 through 7 at Starplex/Armory, sponsored by the C.C. Branch of the Professional Grounds Management Society, a nonprofit organization.

There will be landscaped garden exhibits by local landscape contractors, the Smithsonian, National Arboretum, U.S. Botanic Garden and many others. The Smithsonian Office of Horticulture will have two major exhibits, including a 22-foot-wide flowerfilled Victorian basket and a simulated 19th-century grotto with a waterfall featuring orchids and tropical plants.

Brookside Gardens has designed a small, easily maintained garden perfect for the townhouse or condominium owner. The Potomac Rose Society's exhibit will be a small house garden with roses selected for color and hardiness in the metropolitan area.

Other exhibits will include an herb garden, a woodland retreat with a pond, a hillside garden, several Japanese gardens, and a topiary garden for children with plants grown in the shapes of animals.

Educational exhibits and continuous daily seminars and demonstrations, sponsored by the University of the District of Columbia Cooperative Extension Service, will cover a wide variety of gardening topics.

A few of the many seminar topics include bonsai, home landscaping, how to have healthy house palnts, and vegetable gardening. Seminars on Saturday and Sunday will have signs for the deaf and hard of hearing.

The National Capital Area Federation of Garden Clubs will present a standard flower show -- a show within a show. This section will feature floral arrangements, small landscaped gardens, specimen plants and educational exhibits. Members of local clubs will compete for awards.

The flower and Garden Show will also include a garden marketplace with everything that's new in plants and garden equipment, the popular horticultural arts and crafts gallery, and a Green Thumb clinic manned by experts from area extension services. Another highlight will be the Meet the Media garden, where local radio and television personalities and garden writers will visit at different times. The show will be open from 10:30 to 9:30 except the first day, when it opens at 1, and the last day, when it closes at 8.

Tickets are available at many florists and will be sold at the door. General adult admission is $4, senior citizen tickets are $3, children 6 to 12 $1.50, children under 6 free. There will be a reduction of $1 in the regular adult price between 11 and 3 to Metro riders who present a valid transfer at the ticket counter.

The Starplex/Armory is on the Metro Blue and Orange lines, and has ample parking. Wheel chairs will be available.

Q We plant cauliflower in the spring; it grows fine but the heads never amount to anything. Can you offer any suggestions ?

A One of the main problems with cauliflower planted in the spring is hot weather. The curds (heads) are made up of tight flower bud clusters, and when hot weather sets in they just go to seed, failing to develop a usable head. The curds also can be damaged by frost, so they should be planted outdoors after danger of frost is over. If there is a threat of frost, protect the plants with paper caps. Plant varieties that mature quickest: Snow Crown, a 975 All-America winner, matures in 53 days; Snow Kking Hybrid, also an All-America winner, matures in 50 days.

Q I have a large dogwood tree in the front yard and it needs to be pruned. When is the best time to do it ?

A The best time to prune a dogwood is late winter before growth starts. The dogwood usually is a heavy bleeder -- that is, it loses a lot of sap from cut surfaces. This is not to be considered similar to the bleeding of an animal, and seldom results in harm to the plant. The bleeding usually stops about a month later.

The liquid lost is almost entirely water, and little if any bleeding occurs when the water supply in the soil is not abundant.

Maples and grapes also are heavy bleeders; it may be better to prune maples in early summer to prevent bleeding; grapes should be pruned in late winter before growth starts.

Q Dock seems to grow almost everywhere. Can these wild greens be eaten safely ?

A Specialist say dock, Rumex Crispus, can be used for greens when the young leaves are less than a foot in length, cooked like spinach until tender, and served with seasoning and butter. Make sure of plant identification before eating.

A wash made of roots when they are large enough, soaked in vinegar, is used to treat ringworm, the specialists say; fresh roots boiled in water provide a decoction that can be used internally-as a laxative and a treatment for skin ailments, and crushed green leaves can be applied to bring a boil to a head.

Q My crape myrtle did not bloom last year or the year before. Prior to that it bloomed nicely. Do you have any idea what might be wrong with it ?

A Crape myrtles in this area were badly damaged by winter weather the winters of 1976-77 and 1977-78, and many died. If your plant survived, it probably needs to regain its vigor. A plant growing in heavy shade, where the process of photosynthesis (food production) is affected, may not bloom; one that is badly diseased by powdery mildew will produce poor flowers if it blooms at all. Spraying with ActiDione-PM should provide disease control. Watering the plant occasionally during prolonged dry weather will help it gain strength.

Q -- Soybeans have been much in the news lately and some people seem to think they beans may be the answer to the world's food problem. What do you think?

A It may be they are, but some of the claims for soybeans are a bit exaggerated, according to specialists. The characteristic flavor is a taste one has to cultivate.

They are high in protein and do have at least small amounts of all of the essential amino acids, but so do pinto beans, split peas and lentils. All have the same limiting amino acid -- methionine. Amino acids, the substances that compose the protein molecule, are carried to the body's cells by the bloodstream, and each cell removes the amino acids needed to build its special kind of protein. If the amino acid is missing, the protein cannot be made.

Q My daughter gave me some pussy willow branches for forcing indoors. Can they be used to start a pussy willow for myself ?

A Cutting of pussy willow root very readily in water or planted in the ground. Use cuttings about one foot in length. If you root them in water, plant them outdoors in the ground soon after the roots are an inch long. Handle them carefully because the roots are brittle and break easily.

Q My mother used to have a sweet shrub that was wonderfully fragrant when in bloom. I bought two sweet shrub plants three years ago. They bloom every year but the flowers have little fragrance .

A You probably bought the wrong variety. The flowers of Calycanthus Floridus, the Caroline allspice, are nicely fragrant; those of Calycanthus occidentalis, the California variety, have very little fragrance.

Q We have been spending $50 to $20 every winter for sunflower seeds to feed birds. Last spring we decided to grow our own. The plants came up and grew all right, but the seed that developed were not any good, they were hollow .

A This year plant a variety intended mainly to produce feed for birds, such as Mammoth, which provides tall plants bearing striped seeds that are plump, well-filled and thin-shelled. Moth larvae sometimes damage the seed heads; dusting them with Sevin dust should take care of that. Spittle bugs sometimes are found on the plants, they seldom do much damage. If you have a question for Tom Stevenson, write to him at The Weekend section The Washington Post 1150 15th St. NW Washington, D.C. 20071 .