by Connie Oswald Stofko It’s the sale that gardeners wait all year for— Mischler’s 49-cent perennial sale. Since it comes around only once a year, you should do a little preparation so you can make the most of it. The sale will be held Friday, April 24 to Sunday, May 3 at Mischler’s Florist and Greenhouses, 118 South Forest Rd., Williamsville. (Please note that it starts this Friday; I had the starting date wrong last week.) Sale hours are 8 a.m. to 5 p.m. Monday…