GARDENING Events This Week FALL PLANTING OF TREES AND SHRUBS. Pima County Cooperative Extension. 4210 N. Campbell Ave. Free gardening demonstrations take place on Wednesday, September 25 at 9 a.m. and repeated at 1 p.m. (Wilmot Library). Call 626-5161 for information. IRRIGATION WORKSHOPS. Tohono Chul Park. 7366 N. Paseo del Norte. 742-6455. On Saturday, September 21 from 9 a.m. to noon, learn to build a drip irrigation system; from 1 to 3 p.m., learn why irrigation timers are useful and discuss different types of timers and then build your own. Workshops are free. Call to register at 622-7701. Upcoming ROSES FOR FALL PLANTING. Pima County Cooperative Extension. 4210 N. Campbell Ave. Free gardening demonstrations offer tips on planting and care on Wednesday, October 2 at 9 a.m. (repeated at 1 p.m. at Wilmot Library). Call 626-5161 for details. Announcements COMMUNITY GARDENS OF TUCSON. Start Fall gardening in a plot to suit your needs and a location near you and share seeds, plants and experience with other gardeners. $10 a month covers water costs. Call 795-8823 to reserve a plot.