Spread your picnic blanket on the grounds of Woodlawn Plantation Sunday and enjoy a late summer concert sponsored by the National Trust for Historic Preservation.

Starting at 6:45 p.m., Potomac Brass of the City of Fairfax Band will play a medley of tunes varying from light classical to marching band. In addition, a barbershop quartet will perform. Beer, wine and refreshments will be sold throughout the concert, which ends at 9 p.m.

Woodlawn Plantation is a historic house and museum at Rtes. 235 and 1 in Mount Vernon. Follow signs from I-95.

Admission is $5 for adults and $2.50 for students in grades 1 through 12. Children 6 and under are free. For more information, call Woodlawn Plantation at 780-4000.

Register with Fairfax County public schools to train for employment as a geriatric nursing assistant before classes start Tuesday.

Geriatric nursing assistants address the social, emotional and physical needs of patients in nursing homes. Training focuses on bedside care, charting, taking vital signs and observing and reporting patient progress, among other skills. Attendance at 23 sessions is required to become certified. Classes will be conducted from 3:30 to 6:30 p.m. on Tuesdays and Thursdays until Nov. 12 at Walnut Hill Center, Fairfax. After that, classes will be held from 8 a.m. to 1 p.m. on Tuesdays and Thursdays from Nov. 17 to Dec. 10 at the Fairfax Nursing Center.

There is a comprehensive class fee of $158. Those interested may sign up at the Woodson Adult Center, 9525 Main St., Fairfax. For additional information, contact Frances Moore at 698-0400.

Auditions for the Northern Virginia Jewish Community's production of "The Diary of Anne Frank" will be held at 7:30 p.m. Sunday and Monday at the center.

The cast comprises five women and five men, ages 13 to 60. Those interested should read the script before trying out.

The curtain for "Anne Frank" will go up on Dec. 10, 12 and 13 at Beth El Hebrew Congregation in Alexandria. Cast hopefuls and volunteers should contact the community center at 323-0880. The center is located at 8822 Little River Turnpike, Fairfax.

In celebration of the opening of the Smithsonian Institution's Arthur M. Sackler Gallery, a demonstration of ikebana, the Japanese art of flower arrangement, will take place on Tuesday at the Thomas Jefferson Community Auditorium in Arlington. Also, ikebana workshops will be conducted on Sept. 24 at Westminster Presbyterian Church in Alexandria.

Akihiro Kasuya, headmaster of Tokyo's Ichiyo School of Ikebana, will conduct the demonstration and workshops. Kasuya's floral creations will decorate the entrance pavilion and main lobby of the new museum.

Choice reserved seats for the demonstration on Tuesday cost $15; general admission costs $8. At 10 a.m., supplies for creating floral arrangements will be sold, and the demonstration will begin at 11. The Thomas Jefferson Community Auditorium is located at 3501 Second St. South, Arlington. For ticket reservations and more information, contact Mrs. R. Klementz at 978-3961.

On Sept. 24, workshops will be held from 10 a.m. to noon and from 1 to 3 p.m. for $15 each. A box lunch will be provided from noon to 1 p.m. for $5. Please bring containers, scissors and needle frogs, devices for spacing flowers in an arrangement. Westminster Presbyterian Church is located at 2701 Cameron Mills Rd., Alexandria. For more information, call Mrs. R. Gottfried at 892-8862.