Arbor Day Tree Planting, Dawsonville. 2 p.m. Friday, Rock Creek Park, 445 Martin Road, Dawsonville.Arbor Day, Gainesville. 10 a.m. Friday, Northeast Georgia History Center, 322 Academy St., Gainesville. 770-297-5900.
Winter Botany, Helen. Plant identification without using leaves. 1-4 p.m. Saturday, Smithgall Woods Conservation Park, 61 Tsalaki Trail, Helen. Preregistration required. $5; $5 parking. 800-573-9659 ext. 305.
Bike ride, Gainesville. Chicken City Cyclists. Moderate ride, more than 40 miles. 10 a.m. Saturday, Dewberry Church, intersection of Clarks Bridge Road and Glade Farm Road, Cleveland. firstname.lastname@example.org.
Polar Bear Plunge, Buford. Swim in the icy waters of Lake Lanier. Benefits Special Olympics Georgia. Food, music, plunger costume contest. Gates open at 11 a.m.; plunge at 1 p.m. Saturday, Lake Lanier Islands Beach and Waterpark, 6950 Holiday Road, Buford. $50 minimum in pledges (or personal donation) required for participation. 770-414-9390, ext. 115.
Stars Over Elachee at Chicopee Lake, Gainesville. For adults and kids age 8 and older. View the night sky and learn to use a telescope. Bring a flashlight and pencil. 5:45-7:45 p.m. Saturday, Elachee Nature Science Center, 2125 Elachee Drive, Gainesville. $10 adults, $5 children age 11 and younger, free for Elachee members. 770-535-1976.
Bike ride, Gainesville. Chicken City Cyclists. More than 30 miles; hilly. 10 a.m. Feb. 27, Bolling Mill Park, off Cool Springs Road, Gainesville. email@example.com.
Smithgall Volunteer Orientation and Training, Helen. Seeking volunteers to help plan and carry out park projects. 9-11 a.m. Feb. 27, Smithgall Woods-Dukes Creek Conservation Area, 61 Tsalaki Trail, Helen. Preregister. 706-878-3087.
18th Annual 5K and 1-Mile Fun Run/Walk, Gainesville. Benefits Challenged Child and Friends. Registration, 1 p.m.; fun run, 2 p.m.; 5K, 2:30 p.m.; Tiny Tot Trot and Roll, 3:30 p.m. Feb. 28, Riverside Military Academy, 2001 Riverside Drive, Gainesville. 770-535-8372, ext. 309.
Triathlon Club, Gainesville. No experience necessary. Meets 7 p.m. second Tuesdays, Fit 2 Tri Store, 1292 Thompson Bridge Road, Gainesville. 770-712-9129 or firstname.lastname@example.org.
ISI Cycling ride, Gainesville. 35-45 mile ride. No ride in rain or temperature less than 36 degrees. 1 p.m. Sundays, Kroger Shopping Center, 3630 Thompson Bridge Road, Gainesville. 678-231-0417.