Arboretum open daily dawn-dusk; gates at the north and south end of Arboretum Drive E. are closed during non-open hours. Visitor center open daily 9-5; closed most major holidays. Free 60- to 90-minute guided walks depart from the visitor center Sun. at 1, Jan.-Nov. Tram tours are offered the first Thurs. of the month at 11; reservations are required. Allow 1 hour, 30 minutes minimum.