SALVIND OLSON oversees a cooperative garden. The one-acre community garden in Rock Creek Park is run by committee--128 gardeners who volunteer for a water committee to see that the hoses work properly, a cutting committee to trim the grass, a maintenance committee to tidy supply bins and an inspection committee of five who see that the garden is aesthetically appealing.

As manager, Olson buys the hay for mulching and roto-tills individual plots whenever he's asked. Members chip in a dollar apiece to help pay for the first-aid kit he keeps stocked. Each spring he plants a banana tree. "It doesn't bear fruit," Olson says, "but everyone enjoys looking at it."

This community garden, one of many owned by the National Park Service, is a solution for apartment and house dwellers who want to plant a garden but don't have the space or who want to grow more than their present gardens will hold. Most are free and run by the National Park Service or private community groups who are happy to see a vacant lot cleared of its broken bottles and converted into a bed for glorious food.

Olson's garden is made up of individual plots 20 feet long ranging in width from 10 to 20 feet. Individuals are responsible for their own plots and are free to grow whatever vegetables they choose. No doubt you'll see plenty of tomatoes, limas, green beans and lettuce, he says. But few grow their own herbs--this group maintains a communal herb garden from which members may pick and choose.

"We're a self-contained unit," Olson brags of the garden that has grown from 38 plots to 125 in its eight years of existence. "It works out just fine. We've got lots of different professionals out there--doctors, lawyers, even a rabbi. They all like to get on their knees and play in the soil."

There's something to be said for watching your garden grow. A successful garden is akin to giving birth, say many who have been gardening in Washington for years. It's a thrill to watch tiny seeds sprout, mature and thrive, and a good excuse to get out of the house and into the air on balmy summer evenings. Gardeners' families never have it so good as when served food that often tastes better--and fresher--than what you can buy even at height-of-summer, full-blown farmers' markets. Convinced? Here are some numbers to call to line up a garden for next spring, followed by a list of cataglogs from which to order your seeds. Call for your garden now, they warn, plots are usually assigned on a first-come, first-serve basis. GROW (Garden Resources of Washington, 797-9284): Grow currently has 11 functional community gardens available in all neighborhoods throughout the district. It also has 50 additional lots that need clearing and planting throughout the city to be matched with interested gardeners.

In addition, GROW has a library for members filled with resource books on plants, diseases and planting techniques. There is a monthly newsletter for members. Executive director Tricia Gabany holds educational seminars for groups on planning and garden design, garden pests, soil improvement, starting and managing a community garden, and harvesting and preserving.

GROW will hold a fall harvest festival Sunday, noon to 5 p.m., at 6th and Independence Ave. NW (behind the Air and Space Museum), in its demonstration garden. The festival will feature sales of produce from community gardens, and canned and baked goods. There will also be free seeds, literature and displays of fall bulbs and flowers, and a plant clinic where people can bring in their problem plants for advice. NATIONAL PARK SERVICE

* National Capitol Parks East, 1900 Anacostia Drive SE, Wash. DC 20020. Phone: 472-9227. Because the number of gardens changes frequently, there are no figures on the number of plots available for next year. Gardens are free. Write now for next year's garden to garden coordinator, Cynthia Salter-Stith.

* Rock Creek Park (Garden Coordinator, National Park Service, Rock Creek Park, 5000 Glover Rd. NW., Wash. DC 20015. Phone: 426-6832): There are nine community garden areas with a total of 560 plots, each 25-feet square. They are free to anyone from the metropolitan area, on a first-come, first-served basis. Over 2,000 gardeners participate. Write now for an application to plant next spring. The applicant must indicate gardening experience, preferred location and the name of a back-up person to tend the plot during vacations or illness. Plots will be awarded between October and January. SEED CATALOGS

* W. Atlee Burpee Co., Warminster, Pa. 18974

* Herbst Seedsmen, Inc., 1000 No. Main St., Brewster, N.Y. 10509

* Mellinger's Inc., 2310 W. South Range, North Lima, Ohio 44452

* J.E. Miller Nurseries, Inc., Canandaigua, N.Y. 14424

* Geo. W. Park Seed Co., Inc. S.C. Hwy. 254 N., Greenwood, S.C. 29647

* The Rocky Mountain Seed Company, 1325 15th St., Denver, Colo. 80217

* Spring Hill Nurseries, 110 West Elm St., Tipp City, Ohio 45371

* Van Bourgondien Bros., PO Box A, 245 Farmingdale Rd., Rt. 109, Babylon, N.Y. 11702

* The Wayside Gardens Co., Hodges, S.C. 29695