VEGETABLE- and flower-growing questions, insect and plant disease identification, soil testing, landscaping -- your local extension probably has the answer, once you get through to one of its horticulture hotlines.

"We get from 120 to 140 calls on the hotline every day," estimates Stanton Gill, Montgomery County extension agent. "We have to limit our hours to four each day [9 a.m.-1 p.m.] so we can get to the business of teaching, soil testing, plant clinics, etc." The number to call is 949-6740.

Like the D.C. extension service (last week's HELP), which is operated by the University of the District of Columbia, Maryland's and Virginia's extension services are literally "extensions" of state universities -- the University of Maryland and Virginia Polytechnical Institute, respectively. The extension service program was etablished nationwide in the early 1900s as part of the Land Grant University System.

Information given by the extension services complements each jurisdiction's urban gardening program.

Montgomery County: Extension agents Gill and Dick Biggs run the; urban agriculture division of The Montgomery County Extension Service, 600 S. Frederick Ave., Gaithersburg.

Gill and Biggs hold plant clinics Monday-Friday, 2-4 p.m. at their offices. Gill invites Montgomery County residents to bring in plant samples, diseased vegetables, insects, soil samples -- "whatever you're having trouble with" -- to the clinics. Or mail them, in noncrushable boxes." At the clinics we try to identify the problem and recommend a remedy. We also try to suggest ways the home gardener can avoid this problem in the future."

Classes are offered on a variety of topics, according to Gill. "Last season we gave about 18 classes on fruit tree protein. Someone usually volunteers their back yard as a meeting place."

"We publish an urban agriculture newsletter called 'Hotline' that lists the classes," adds Gill. To get on the mailing list, call or write the extension service. Gill also puts out "Vegetable Short Notes" that give time advice on the season's vegetables.

Also underway in Montgomery County, notes Gill, is the Integrated Pest Management Program, which currently operates only in Olney and Silverbrook. In this program, a University of Maryland student scouts an area, looking for insects and diseases that could become potential community problems. "We recommend what should be used to combat the problem, using a minimal amount of pesticides, fungicide, insecticide or whatever.

"The fewer chemicals used on your plants, lawn and trees, the better. One of our most important aims is to educate the public to differentiate between a disease and insect problem. It's a waste (and not great for your health) to spray an insecticide on your garden when the problem calls for a fungicide. On top of the first remedy, a second will have to be sprayed. A lot of people have trouble telling when to use which remedy.

"In Springbrook, we were able to reduce pesticide use by 40 to 50 percent with the Integrated Pest Management Program," says Gill, who is also an entomologist.

The Maryland extension service operates year-round, including classes in the late fall on landscaping and, in the winter, courses on fruit and vegetable garden planning.

Gill and Prince George's County extension agent Ray Bosmans co-host a weekly horticulture radio show on WGTS (91.9 FM). "Plant Talk" airs every Tuesday, 10-11 a.m. and is anchored by horticulturist Terry Pogue.

"During the second part of the program, listeners can call us at 279-0101 with questions," says Gill. Prince George's County

Donna Rosenbloom, consultant with Prince George's County extension service, says: "We have publications on everythying ranging form trees and lawn pests to landscaping and house plants.All are available at no charge by callaing our hotline (952-3226)."

Like Montgomery County, Prince George's County's hotline is open to the public on a limited basis: Monday and Wednesday, 9 a.m.-noon; Tuesday, Thursday and Friday, 1-4 p.m.

Rosenbloom, who works with extension agent Bob Stewart and Ray Bosmans, admits that in spite of the hotline schedule, the phones ring off the hook throughout the day.

The Prince George's County office, at 15209 Marlboro Pike in Upper Marlboro, maintains a garden on its property where plant clinics and demonstrations are often held, according to Ray Bosmans, who like Gill is also an entomoligist.

Stewart and Bosmans give many talks throughout the county at public libraries, garden clubs and neighborhood communities, says Rosenbloom. To arrange for a meeting in your community, Rosenbloom suggests calling the hotline.

To get your soil tested, also phone the hotline request a soil test kit. "We send the sample to the University of Maryland, where it is analyzed," explains Rosenbloom. "They test it for potassium, magnesium and phosphorous content as well as test for acidity. All these factors are important in varying degrees, depending on what is being grown."

"Once we get the results back from the university labs, we report back to the county gardener with our recommendations." Fairfax

In Northern yvirginia, the extension services offer an intensive gardening program called "Master Gardeners." In exchange for 50 hours of gardening lectures, demos and workshops with experts from VPI, the participant gives the extension service 50 volunteer hours -- manning the hotlines, working the Farmers' Market (see below) -- "There's always something for them to do," says Fairfax extension agent Charlie Hall.

Members of the National Capital Federation of Garden Clubs are trained in the Master Gardeners program. Their work at the federation is another way the county gets back its investment. During the growing season, says Hall, the members hold clinics every Saturday, 10 a.m.-2 p.m. Clinics are usually held at the following: George Mason Regional Library in Annandale; Kings Park Library in Burke, Va., Centreville Library; Central Library in Fairfax; Chesterbrook Shopping Center in McLean; Reston Regional Library; Richard Byrd Library in Springfield; and Patrick Henry Library in Vienna.

The Fairfax County Extension service, 3945 Chain Bridge Rd., operates its hotline Monday-Friday, 8 a.m.-4:40 p.m. Call 691-3456.

"We encourage residents to bring us -- or mail to us -- samples of their plant problems, from damaged leaves to insects," says Hall. "The samples can also be dropped off at branches of the public library."

"Soil testing kits can also be picked up and returned at the library branches. Once the soil is examined at our university labs at VPI, we send the resident our suggestions in about three weeks."

For timely gardening advice, Hall suggests putting yourself on the mailing list of the service's newsletter. Residents can also call the service's Dial-A-Tape (691-3240) to request one of their two-minute horticulture tapes.

Another service the Fairfax office provides is CHIPs -- the Community Home Improvement Program, which provides speakers to community groups on horticulture topics. Arlington

Extension agent Betty Eyler says many of the people the service trains in the Master Gardeners program pay back their time at Arlington's Farmers' Market, held every Saturday, 7 a.m.-noon at the Arlington Court House parking lot, 14th Street and Court House Road.

Like the other extension services, Arlington's offers residents plant clinics, soil testing, insect and disease identification as well as speakers. Call 558-2475 Monday-Friday between 8 a.m. and 5 p.m.

Eyler says samples can be brought in or mailed to the office at 855 N. Edison St., Arlington, Va. 22205.

Plant clinics are listed in the bi-monthly newsletter, says Eyler. "One of our largest clinics is offered annually at the Arlington County Fair Aug. 21-23 at the Thomas Jefferson Community Center."

The Arlington County Extension services operates the garden plots in Arlington.

"Unfortunately," apologizes Eyler "all are taken this year. But as of Jan. 1, 1982, residents can sign up for next season." Plots costs $10 for either 20-by-30 or 30-by-30 square feet. Alexandria

In Alexandria, explains horticulture extension agent Bruce White, the Recreation Department and Blessed Sacrament Church administer the gardening plots, while the extension service supplies the community gardeners with newsletters and year-long gardening suggestions. The Alexandria office is at 901 Wythe St. (Rt. 1) and can be reached by calling 838-4333, Monday-Friday, 8:30 a.m.-5 p.m.

White says that in addition to gardening workshops on soil improvement, vegetable growing, insects and disease, the Alexandria service offers a course on intensive cropping -- getting the maximum number of crops for a minimal amount of space.

White, who works alone in the horticulture division, says "I get a lot of help from volunteers who have taken the Master Gardeners program. They help on the newsletters. This summer three or four of them will join me in regular evening and Saturday visits to urban gardening sites, where we'll speak with the gardeners, identifying insects and diseases for them, etc." White says they're still setting up the schedule.

Another program being initiated in Alexandria is Master Food Preservers. "It will operate like Master Gardeners, but will be run by the home economics division of the extension service," says White.