How do you make your beautiful hydrangeas last in a bouquet? At UNH’s Woodman Horticultural Research Farm, Becky Sideman, UNH professor of horticulture, is growing 19 varieties of cold-hardy hydrangeas that florists could use as cut flowers: arborescens, like the one she cuts here, panicle and oak leaf. She’s found that arborescens and panicle varieties “basically grow themselves,” but she steers clear of the classic blue macrophylla hydrangeas, which don’t bloom reliably in our Northern New England climate.