Introduce your child to farm, forest and other ecological landscapes with "Farm and Forest Explorers" at Land’s Sake Farm, 90 Wellesley St., Weston, taking place Sept. 15 to Nov. 5 on Tuesdays and Thursdays, 3-5pm. Participants witness the effect of the changing season on the farm landscape and learn about natural life cycles. They will also harvest pumpkins and cherry tomatoes, pick fall raspberries, and spend time with the chickens as they start laying eggs.   Cost is $250 for the eight-week program for non-members, $220 for members.  Meanwhile, the Green Power After School program allows participants to further their farm education by engaging with the land beyond the summer months. During the fall, students join the end-of-season harvest, gain experience with fall crops, and learn how to prepare the earth for winter.  Dates are Sept. 10 to Nov. 2 on Mondays and Thursdays, 3-5pm at Green Power Field on Merriam Street.   Cost is $220 for eight-week session for members, $250 for non-members.