Preview 8 a.m.; plant and book sale, how-to garden demonstrations 9 a.m.-noon at AgriLife Extension Office, 3033 Bear Creek Drive; 281-855-5600, hcmga.tamu.edu. With Jason McKenzie. 10 a.m. at the Arbor Gate, 15635 FM 2920, Tomball; 281-351-8851; arborgate.com. Texas gardening with fall flowers clinic: 10:15 a.m. at Cornelius Nursery, 1200 N. Dairy Ashford and 2233 S. Voss; calloways.com/clinics. Build your own rain barrel workshop: 1-3:15 p.m. or 3:30-5:45 p.m. at the Houston Arboretum and Nature Center, 4501 Woodway; 713-681-8433; register at houstonarboretum.org. $80 members, $95 nonmembers. Fall festival with plant societies, local artists specializing in garden art, children’s activities. 8 a.m. to 4 p.m. at Mercer Arboretum and Botanic Gardens, 22305 Aldine-Westfield, Humble; 281-443-8731; hcp4.net/mercer. Organic Horticulture Benefits Alliance-Texas AgriLife event. 7:30 a.m.-3:30 p.m. at Texas Agri- Life Extension, 3033 Bear Creek Drive.