May is a wonderful time to get outdoors and take advantage of walks, workshops, plant sales and educational programs. For all events, call to see if pre-registration is required. If a fee is not shown, the event is free.

The District

Hillwood Estate, Museum & Gardens: 4155 Linnean Ave. NW, 202-686-5807, hillwoodmuseum.org

United States Botanic Garden: 100 Maryland Avenue SW, 202-225-1116, usbg.gov

U. S. National Arboretum: 3501 New York Avenue NE, 202-245-4521, usna.usda.gov

l Ongoing through June 12: Spring garden tours. Docent-led tours offered on a first-come, first-served basis Tuesday through Saturday, 10:30 a.m. and 12:30 p.m. Sunday, May 8 and 29 at 2:30 p.m. Tickets distributed at the visitor center upon opening each day. Donation suggested. Hillwood.

l  May 1: Renovation and Renewal in Fern Valley. Horticulturist and curator Joan Feely will guide you through the recently redesigned 50-year-old fern valley native plant collection. 4-6 p.m. $12. U.S. National Arboretum.

l  May 2, 9, 16, 23: Lunchtime tour of conservatory. Guides link the exotic plant world to everyday life. Noon-1 p.m. U.S. Botanic Garden.

l  May 4, 8: Azalea collection walking tour. Join horticulturist and curator Barbara Bullock for a tour through thousands of blooming azaleas and learn their origins. May 4, 5-7 p.m.; May 8, 10 a.m.–noon. $12. U.S. National Arboretum.

l  May 6, 7: Flower mart. The plant sale focuses on Austrian culture. May 6, 10 a.m.-6 p.m.; May 7, 10 a.m.-5 p.m. Washington National Cathedral, Wisconsin and Massachusetts avenues NW, allhallowsguild.org.

l  May 6-8: Potomac Bonsai Festival. Annual festival including demonstrations, lectures, workshops, exhibits and vendors. Potomac Bonsai Association members and visiting bonsai artists share their expertise. Rain or shine. 9 a.m.-5 p.m. Call for fee-based programs. U.S. National Arboretum.

l  May 6, 7: Garden Fest-Hillwood on the National Mall. Celebrate National Public Gardens Day on the Mall at the Smithsonian Institution’s annual Garden Fest. May 6, 11 a.m.-1 p.m.; May 7, 11 a.m.-3 p.m. Donation suggested. Hillwood.

l  May 7: Herb Day. Annual celebration by the Herb Day Coalition to enhance public awareness of the significance of these plants. 1-4 p.m. U.S. National Arboretum.

l  May 7: Annual Herb Day. Focuses on ways to use herbs safely and creatively for health, beauty and culinary enjoyment. Demonstrations and tours. 10 a.m.-4 p.m. U.S. Botanic Garden.

l  May 7, 21, 28: National Garden Tour. View trees and shrubs of the Mid-Atlantic region and learn what will grow well in your garden. Canceled in rain or severe weather. 1–2 p.m. U.S. Botanic Garden.

l  May 8: Mother’s Day tour of rose garden. Join rose expert Sharon Hanes and learn about the U.S. national flower at the National Garden. Canceled in rain or severe weather. Noon-1 p.m. U.S. Botanic Garden.

l  May 8, 29: Serene Sundays. Stroll the mansion and spring gardens. Donation suggested. 1-5 p.m. Hillwood.

l  May 10: Medicinal and poison plants. Beth Burrous, a biochemist, will point out poisonous and medicinal plants discussing famous, interesting and sometimes fatal cases of poisoning. Noon-1 p.m. U.S. Botanic Garden.

l  May 14: Shade tree walk. The walk will focus on larger shade and canopy trees growing in the landscape. Learn basic identification skills and outstanding characteristics that make trees aesthetically appealing. The walk will cover a moderate distance over hilly and uneven terrain. 9-11 a.m. U.S. National Arboretum.

l  May 14: Open house. World Bonsai Day honoring the memory of bonsai master Saburo Kato, founder of the World Bonsai Friendship Federation. Curator-led tours 11 a.m.-3 p.m.; continuous demonstrations. 10 a.m.-4 p.m. U.S. National Arboretum.

l  May 19, 26: Margaret Hagedorn Rose Garden. Join rose expert Sharon Hanes and tour this formal garden dedicated to growing “old roses” and “modern roses” without using fungicides or insecticides. May 19, noon-1 p.m.; May 26, 5:30-6:30 p.m. U.S. Botanic Garden.

Maryland

Brookside Gardens: 1800 Glenallan Avenue, Wheaton, 301-962-1400, brooksidegardens.org

l  Ongoing through September 18: Wings of Fancy live butterfly exhibit. Hundreds of North American, Costa Rican and Asian butterflies surround you as they fly around this indoor exhibit. Daily 10 a.m.-4 p.m. $6 adults; $4 children. Recorded information is available at 301-962-1453. Brookside.

l  May 1: Azalea show and sale. Sponsored by Brookside Gardens Chapter Azalea Society. 9 a.m.-4 p.m. Brookside.

l  May 6: Hanging-basket workshop. Create your own display of flowers and foliage. Instructions will cover planting tips and how to line a 14-inch wire basket with sphagnum moss. 0-11:30 a.m. and 1:30-3:30 p.m. $45. Brookside.

l  May 7: Annual garden mart. Sponsored by Silver Spring Garden Club. 9 a.m.-3 p.m. Brookside.

l  May 7, 14, 21, 28: Garden walks. Meet at the visitors-center exit at the rear of the building. 2 p.m. Brookside.

l  May 11: Butterfly container. Create a container garden that will support the entire butterfly life cycle and encourage butterflies to live in your garden. Workshop fee includes a 14- inch container, butterfly plants and instructions. 1-3 p.m. $44. Brookside.

l  May 14: Chesapeake Ecology Center garden tour. Tour a shade garden from 9-10 a.m.; seedling potting and garden care is discussed from 10 a.m. to noon. Adams Academy at Adams Park, 245 Clay Street, Annapolis, chesapeakeecologycenter.org

l  May 17, 18: Hosta-container workshop. Join Joan O’Rourke and create a container for your deck or patio out of a deer’s reach. Workshop fee includes all materials. 10-11:30 a.m. $44. Brookside.

l  May 20, 21: Conservation landscaping techniques. Learn conservation-based landscaping techniques, restore native habitats and improve the environment. Develop a site design and learn about a county rebate program. 10 a.m.-1 p.m. $10. Brookside.

l  May 25: Soil microbes. Learn how to improve your soil in order to grow healthier and more-productive vegetable gardens. 1:30-3:30 p.m. $18. Brookside.

Virginia

Green Spring Gardens Park: 4603 Green Spring Rd., Alexandria, 703-642-5173, greenspring.org

Meadowlark Botanical Gardens: 9750 Meadowlark Gardens Court, Vienna, 703-255-3631, nvrpa.org/park/meadowlark_botanical_gardens

University of Virginia, Blandy Experimental Farm, State Arboretum of Virginia, 540-837-1758, virginia.edu/blandy

l  April 30: Parkfairfax Native Plant Sale. 9 a.m.-2 p.m. 3601 Valley Drive parking lot. Alexandria. http://home.earthlink.net/~sknudsen/

l  May 1: Native American woodlands walk. Tour the Potomac Valley native plant collection with emphasis on how Native Americans used plants for survival. 2 p.m. Meadowlark.

l  May 5: Wildflower walk. A naturalist guides you through this hike at Thompson Wildlife Management Area. Includes a stop at Fox Meadow Winery for a bring-your-own picnic lunch. (Optional wine tasting $5.) 8:30 a.m.-3:30 p.m. $64. Green Spring.

l  May 7: Invasive-plant removal day. The statewide event, coordinated by the Virginia Native Plant Society and the Virginia Master Naturalists, will take place at various locations. Check online at virginiamasternaturalist.org/invasives/.

l  May 7: Native plant sale. Friends of Riverbend Park will hold its annual plant sale. 8 a.m.- noon. Great Falls Pavilion. Call 703-759-9018 for directions.

l  May 7: Edibles and ornamentals. Incorporate edibles into the ornamental landscape and enjoy having fresh fruits and vegetables outside your door. 9:30-10:30 a.m. $10. Green Spring.

l May 7, 8: Garden fair. Vendors will offer native plants, herbs, shrubs, trees, perennials and other garden items. Children’s activities, information and food. May 7, 10 a.m.-4 p.m.; May 8, noon-4 p.m. $10 per car. State Arboretum of Virginia.

l  May 14: Spring garden day plant sale. Rare and unusual plants will be available from more than 40 vendors. 9 a.m.-3 p.m. Green Spring.

l  May 21: Ornamental grasses. Master gardeners will show you how to select, plant and maintain the best ornamental grasses. 9:30-10:30 a.m. $10. Green Spring.

l  May 21: Iris show. The Chesapeake and Potomac Iris Society will present its annual exhibit in the visitor center. 1-3 p.m. Meadowlark.

l  May 22: Gardening with deer. Staff members share their best tricks for avoiding damage when Bambi and friends visit your garden. 2-3 p.m. Meadowlark.

l  May 30: Twilight hike. Join a park naturalist for an after-dark tour. Learn about the history of the property, wildlife and plant life. Bring a flashlight. 8:30-10 p.m. $5. Meadowlark.

Joel M. Lerner is president of Environmental Design in Capitol View Park, Md.