Celebrate the arrival of spring with a visit to the annual herb sale at the Lyman Estate Greenhouses in Waltham, from Thursday, April 29 – Sunday, May 2, and again on Saturday and Sunday, May 8 and 9, from 10 – 4.  Thousands of naturally grown culinary, medicinal, and ornamental herbs will be on sale.  Scented geraniums, herbal topiaries, pottery, and garden gifts are also available, and the horticultural staff will be on hand to offer expert advice.  Free admission.  Call 781-891-1985, or log on to www.historicnewengland.org for directions and more information.