Nature

Audubon Naturalist Society

Woodend Sanctuary, 8940 Jones Mill Road, Chevy Chase. 301/652-9188 or www.audubonnaturalist.org

• The largest and oldest independent environmental organization in the region.

Hillwood Museum and Gardens

4155 Linnean Ave. NW. 10 a.m.-5 p.m. Tuesday-Saturday. Closed January and national holidays. $5-$12. 202/686-8500; information and advance reservations 202/686-5807 or reservations@hillwoodmuseum.org.

• Spring garden tours. Docent-led tours explore the history of the gardens and identify the scores of plants, including lilacs; irises; Japanese pieris; daffodils; forsythia and spring-flowering shrubs and trees; azaleas; crabapple, dogwood and cherry trees; tulips; and rhododendron. 10:30 a.m., 12:30 p.m. Tuesdays-Saturdays; 2:30 p.m. April 13 and 27. April 8-June 22. Admission included in estate donation.

• Symposium: “Paris on the Potomac.” Cynthia R. Field and Isabelle Gournay, authors of the new book “Paris on the Potomac: The French Influence on the Architecture and Art of Washington, D.C.,” join Hillwood senior curator Liana Paredes and Cynthia Mills of the Smithsonian American Art Museum in seminars examining interior decoration, city planning, architecture and sculpture. Book signing and mansion tour conclude the day. 9:30 a.m.-4 p.m. April 11. $15-$20. Fee includes boxed lunch.

National Aquarium in Baltimore

501 E. Pratt St., Baltimore, at the Inner Harbor. 10 a.m.-4 p.m. Monday-Thursday; 10 a.m.-8 p.m. Friday; 10 a.m.-5 p.m. Saturday, Sunday. Admission $12.95-$21.95, with a range of packages at $14.95-$28.95. 410/576-3800, 410-659-4278, www.aqua.org. Tickets through the Web site or ticketmaster.com, both with service charges.

• Hundreds of exhibits with more than 16,500 animals. Popular exhibits include “Animal Planet Australia: Wild Extremes,” “Frogs! A Chorus of Colors,” “Play! The Dolphin Show” and the new 4-D Immersion Theater. See the Web site for details.

National Aquarium in Washington, D.C.

U.S. Department of Commerce building, 1401 Constitution Ave. NW. 9 a.m.-5 p.m. daily; last admission 4:30 p.m. Closed Christmas and Thanksgiving. Admission $2.50-$5. 202/482-2825, www.nationalaquarium.com

• Animal keeper talks and animal feedings 2 p.m. daily: sharks Monday, Wednesday, Saturday; piranhas Tuesday, Thursday, Sunday; alligators Friday.

National Zoological Park

3001 Connecticut Ave. NW. Grounds open 6 a.m.-8 p.m. daily, buildings 10 a.m.-6 p.m. daily through Oct. 31. Free. 202/633-4800, nationalzoo.si.edu

• Kids’ Farm. New 2-acre exhibit helps children understand where food comes from. Cows, donkeys, goats, vegetable garden. Opportunities to groom the goats and donkeys. Near the zoo’s Rock Creek Park entrance, at the bottom of Olmsted Walk. 10 a.m.-6 p.m. daily through Oct. 31. Free.

Planetarium: David M. Brown Planetarium

1426 N. Quincy St., Arlington. Admission $2, $3. No reservations needed. Doors open 15 minutes before the show. 703/228-6070, www.apsva.us/planetarium

• “Just Imagine.” Exploring “what-if?” questions such as the Earth without a moon, the sun as a different kind of star and more. Ages 10 and up. 7:30 p.m. Fridays, Saturdays; 1:30 and 3 p.m. Sundays. Through April 27.

• Public multimedia programs 7:30 p.m. Friday, Saturday; 1:30 and 3 p.m. Sunday during school year. Stars Tonight program, live interactive talk with the planetarium director and a dome full of stars, 7:30 p.m. first Monday of the month (second Monday when first Monday falls on a legal holiday) during the school year.

Planetarium: The Einstein Planetarium, National Air and Space Museum

Independence Avenue and Fourth Street SW. 10 a.m.-5:30 p.m. daily. Metro: L’Enfant Plaza. 202/633-1000, www.nasm.si.edu/visit/theaters/planetarium. Imax theater schedule: 877/932-4629.

• Planetarium shows: “Cosmic Collisions,” “Infinity Express,” $6.50-$8.50; call for showtimes. “The Stars Tonight — Open Your Eyes to the Skies,” 11:30 a.m. Tuesday, Thursday, Saturday. Free.

Planetarium: Rock Creek Park

Nature Center, 5200 Glover Road NW. 9 a.m.-5 p.m. Wednesday-Sunday. Closed major holidays. 202/895-6070 or www.nps.gov/archive/rocr/planetarium

• The only planetarium in the National Park system. Planetarium shows 1 p.m. Saturday, Sunday for children 4 and older; 4 p.m. Saturday, Sunday for children 7 and older. After-school show 4 p.m. Wednesday. Outdoor evening stargazing sessions once a month April-November at adjacent Military Field, off Military Road.

Second Chance Wildlife Center

7101 Barcellona Drive, Gaithersburg. 9 a.m.-5 p.m. daily. 301/926-9453, www.scwc.org

• The only rehabilitation facility for wildlife in the metro area, offering volunteers the chance to care for orphaned and injured wildlife, especially newborns.

U.S. Botanic Garden

100 Maryland Ave. SW, adjacent to the U.S. Capitol. Conservatory 10 a.m.-5 p.m. daily; National Garden 10 a.m.-5 p.m. through May 31. Free. 202/225-1116, www.usbg.gov

• “An Alphabet Garden of Orchids.” Annual show of hundreds of orchids, including rare and endangered species, from the collections of the U.S. Botanic Garden and the Smithsonian Institution’s Horticulture Services Division. Through April 13.

• “How Plants Work: A Guide to Being Green.” The daily realities of life as a plant. East Gallery. Permanent exhibit.

U.S. National Arboretum

3501 New York Ave. NE. 8 a.m.-5 p.m. daily. Closed Christmas and federal holidays. Free. 202/245-2726 or www.usna.usda.gov

• Potomac Viewing Stone Group Exhibit. Stones, suisecki (Japanese viewing stones) and scholars rocks from members’ private collections. National Bonsai and Penjing Museum. 10 a.m.-4 p.m. Through April 6. Free.

• Full Moon Hikes. Arboretum grounds regardless of weather. 8-10 p.m. April 19 and 20 (both full) and May 19 and 20 (both full). $19. Registration required online or by mail; 202/245-4521 for information.