Free horticultural advice is available by telephone. If you prefer, you may bring your ailing plant to your county extension office. Be sure to call first and ask if an appointment is necessary. Should they be unable to help, they'll send a sample of your plant to a university for no-cost analysis and diagnosis. Free clinics and classes are held most of the year.

Alexandria Extension Office 838-4333. Mon.-Fri., 8 a.m.-5 p.m.

Arlington County Extension Office Hort Line 558-2475. Mon.-Fri., 8:30 a.m.-12:30 p.m.; 1-5 p.m.

D.C. Hort Line 282-7400. Mon.-Fri. 9 a.m.-noon.

Fairfax County's Green Spring Farm Park 642-5174. Tues.-Sat., 9 a.m.-5 p.m., Sun., noon-5 p.m. Walk-in help available.

Howard County Extension Office (301) 992-2030. Mon.-Fri., 8:30 a.m.-4:30 p.m.

Montgomery County/Brookside Gardens, Wheaton. 949-8227. Help and program information available Tues.-Thurs., 9:30 a.m.-noon.

National Diagnostic Houseplant Laboratory, 257 Midland Ave., Lexington, Ky. 40502. Request questionnaire and plastic bag for leaf samples. Return them with $6.85. Three-page diagnosis and advice on reviving plant sent in 72 hours.

"Plant Talk" 10 a.m. Tuesday, WGTS (91.9 FM). Interview/call-in show hosted by Terry Pogue. Will cover tropical foliage for offices, homes, and balconies as well as care and feeding of gift plants (today and Feb. 26).

Prince George's Extension Office 952-3226, Mon. & Wed., 9 a.m.-noon; Tues., Thurs., & Fri., 1-4 p.m.

U.S. Botanic Gardens 225-8333, Mon.-Fri., 9 a.m.-5 p.m.

U.S. National Arboretum 475-4829. Mon.-Fri., 8 a.m.-4:30. Marc Cathey, director. Cathey hosts call-in talk show on WNTR (1050 AM) 9-11 a.m. Saturdays.