Q: I have read that when starting perennials from seed in winter, you should put the flats outdoors. But isn’t it best to keep them under lights indoors? — Sophie Smith, Charleston, S.C.
A: A number of perennials won’t sprout until the seed has experienced a spell of low temperatures. You can make this happen — through a process called stratification — by setting containers of soil mix planted with seeds in a refrigerator or other cool spot (35º to 45ºF) for six to eight weeks, and then moving them someplace warmer (60º to 70ºF); if they haven’t germinated in the fridge, the seeds will sprout within one to four weeks. Many gardeners prefer to skip the fuss of indoor stratification, choosing instead to put flats of seeds directly outdoors so that perennials requiring different temperatures to germinate will come up at their own pace. It’s advisable to place the starter trays outside in a cold frame or under some other cover, such as a porch roof, where heavy rain can’t wash away soil or seed. Then, providing you water the seedlings occasionally, you can let nature take its course. Transplanted into the garden, from midsummer to fall, they will be big, healthy performers during their second spring.