Unusual tropical food plants: Workshop focuses on natural growing methods for small farmers and gardeners, 9:30 a.m. to 4:30 p.m. Saturday and Sunday in Kona. Includes tour of a developing agroforestry farm. Costs $60. Call Kim Wilkinson at 324-4427, Big Island.

Yo-yo demonstration and contest: State champ Alex Garcia performs basic and advanced maneuvers, noon Saturday, Salt Lake Shopping Center. The yo-yo contest this day will decide who enters the state semi-finals July 7 at Ala Moana Center. Call 942-8799.

Israeli dance workshop: With David Barzilay from Israel, 7 to 10 p.m. Saturday, UH-Manoa's Studio 2. Costs $8. Call 623-3603.

Sierra Club trail building: Help work on the Maunawili Falls access trail, Sunday, June 22, 23 and 30. Bring backpack, lunch, two liters of water, shoes and rain gear. Call 538-6616.

Kaipapau Gulch hike: Encounter a dirt road, stream crossings and slippery rocks on the way to a scenic waterfall and plunge pool, with Grant Oka of the Hawaiian Trail and Mountain Club, 8 a.m. Sunday. Eight miles in Hau'ula. Costs $2. Call 521-1300.

Learn to swim: The American Red Cross has free classes for children on Saturday mornings and adults on Monday, Wednesday and Thursday evenings at Ala Moana Beach. Call 734-2101 ext. 123 or 124.

Tai chi at Honolulu Zoo: Practice of Chinese martial art begins 8 a.m. on the first and third Wednesdays of each month. Costs $6 general, $4 kama'aina, $2 with Yum Yum Tree senior card, $1 children, and free for kids 5 and younger. Call 971-7174.