Louis Bauer is Wave Hill’s Director of Horticulture.
Situated off the east side of the Potting Shed, the cold frame, so named because it is not heated, sits about a foot and half below ground level, with a cover of fiberglass windows that provide a consistently cool temperature—just above freezing—for plants in the garden that would struggle to get through the wild swings that are typical of our winter weather. Usually full, or close to full, by mid-December, our cold frame is filling up later than usual, thanks to the month’s worth of unusual warmth we’ve been experiencing this year. We’ve counted only a couple of frosty nights so far. As you can see, all the plants have plenty of elbow room at this point.
Wave Hill Gardener Harnek Singh has brought in young perennials, while Assistant Gardener Coralie Thomas has added in some of the young herbs and flowering plants in the Herb & Dry Gardens that like a milder climate and fast-draining soil. Here the two are in the midst of making some additions to the frames on a recent sunny morning.
The cold frame offers an equally valuable resource for accelerating the growth of some of our flowering perennials, like foxglove and delphinium. The tall delphinium, for instance, which you will find in the Flower Garden in the early summer, are typically hard to grow without winter protection and the benefit of starting in a pot. So, Harnek will collect seeds in July or August, as soon as the plants begin to produce them. (In the crowded garden, few would manage to germinate and grow, but in pots they take off and then continue to thrive in the cold frame.) The Flower Garden also displays many species and hybrids of foxglove, which add a lot of visual spice to the look of the garden, but these types of foxglove will truly reach their full potential only if protected when our icy, wet winter arrives. The cold frame makes for a perfect home away from home for them.
Once the cold frame is in operation, we’re tending it closely, opening and closing its transparent covers manually as the temps rise and fall. It’s rather labor-intensive, but immensely satisfying as we watch the seedlings flourish and eventually find a home back outside in late spring.
In the summer, by the way, we take the doors off the cold frame and transform it into a kind of shade house, an open space we use as a holding yard for growing in the hot months.