Despite what the calendar says, it isn't really spring until the annual plant sale takes place in the Regional Parks Botanic Garden at Tilden Regional Park in the Berkeley hills.

This year the sale will be from 10 a.m. to 3 p.m. April 20, rain or shine. California native plants suitable for every garden environment will be sold, including many not found at commercial nurseries. Trees, shrubs, ground-cover plants, grasses, bulbs, ferns and annuals are all part of the selection. Garden volunteers and staff will be on hand to offer advice and tips.

It's best to arrive early to ensure a wide choice. Garden gates open at 8:30 a.m., and the lines start to form then. The sale starts at 10 a.m.; all proceeds help fund garden programs. Bring cardboard boxes to carry home your purchases. The garden is at the intersection of Wildcat Canyon Road and South Park Drive. Parking and garden entry are free.

Photo lessons: Elsewhere at Tilden, there will be a wildlife photography program from 2 to 3:30 p.m. on April 13. Naturalist Trent Pearce will show how to take telephoto photographs using a hand-held camera and a spotting scope. Bring a point-and-shoot camera (non SLR) or a camera-equipped smartphone.

Bees and their sweet product will be the theme of a honey-tasting program from 2 to 3 p.m. April 14, led by interpretive student aide Morgan Rani Evans. Both programs are free. Meet at the Environmental Education Center at the north end of Tilden's Central Park Drive. Details: 510-544-2233.

Crab and sourdough: The felicitous combination of Dungeness crab and San Francisco sourdough, and how it came to be, will be one of the topics during a walk for ages 9 and older through the Eastshore State Park from 10 a.m. to 2 p.m. April 14, led by naturalist "Trail Gail" Broesder. The group will stop for a no-host lunch at the Seabreeze Market in Berkeley. Details: 510-544-2233.

EARTH DAY FUN: The East Bay Regional Park District and Alameda will celebrate Earth Day with fun activities and beach cleanup 8:30 to 10 a.m. April 20.

Students 10 and older can earn community service hours. Advance registration is required. To register, call 888-327-2757, select option 2 and refer to course 1572.

Afterward, the Earth Day celebration is 10 a.m. to 3 p.m. at Crab Cove Visitor Center, 1252 McKay Ave., Alameda. It will feature activities, giveaways, and food and beverages for sale. For details, call 510-544-3187. Crab Cove is also holding a two-session docent-training for ages 18 and up on how to help the naturalists with programs on Bay and redwood forest ecology. Classes are 10 a.m. to 4 p.m. April 21 and 28. Lunch is provided.

Hikes for Tykes: That series of 1-mile hikes for small children accompanied by a parent continues with a walk from 10:30 to 11:30 a.m. April 16 at Redwood Regional Park in Oakland, led by naturalist Francis Mendoza. Meet at the Trudeau Training Center at 11500 Skyline Blvd. near the intersection with Joaquin Miller Road. Bring a snack for your young one. For details, call 510-544-3187.

Email Ned MacKay at nedmackay@comcast.net.

wild, wildflowers: Two upcoming programs will take advantage of the wildflower displays at Sunol Regional Wilderness, which are usually among the best in the East Bay.

The first is "Walking With Wildflowers, from 9:30 a.m. to 12:30 p.m. April 20. It's a 2½-miler with moderate hills, designed for ages 7 and older and led by naturalist Cat Taylor. The second is a hilly, 2-to-3-mile hike to see how geology and flowers interact. It's led by naturalist Katie Colbert from 1:30 to 4 p.m. April 21. Both hikes are free but require registration. Call 888-327-2757, and select option 2. For Cat's hike, refer to program 1654. For Katie's, the number is 1657.

ANTIOCH: At Black Diamond Mines Regional Preserve in Antioch, naturalist Bob Kanagaki will lead a walk from 9:30 to 11:30 a.m. Saturday to explore how plant distribution depends on sun, water, soil and bedrock. The hike is for ages 7 and older. Rain cancels. Meet at Black Diamond Mines' uppermost parking lot at the end of Somersville Road, 5 miles south of Highway 4. For information, call 888-327-2757, ext. 2750.

Email Ned MacKay at nedmackay@comcast.net.