You don’t need a greenhouse to grow orchids. Achieve success on your own windowsills. Lyman Estate horticulturist Lynn Ackerman teaches the essentials of growing orchids: media, light, water, temperature, fertilization, selection, on Saturday, November 10 from 10 – noon at the Lyman Estate Greenhouses, 185 Lyman Street in Waltham. Registration is required at www.historicnewengland.org, or by calling 781-891-1985.  $25 fee.