The cold frame arrived on December 20. It is a thing of beauty, although a far cry from the traditional country cold frame, which usually consists of an old window propped up against a south wall, and a rough wooden box set directly on the soil. This one, designed and engineered by Mark Morrison and his team at Windsway (see “The Team” link above), is built from heavy aluminum framing, safety glass and hinges reminiscent of the bulk-head of a nuclear submarine. A heating pad using very little power gives a margin of safety against freezing on the coldest winter nights. Such are the demands of farming on the 35th floor, where conditions are harsh, and everything must be designed to anticipate the consequences of a Force 5 hurricane or tornado sweeping through New York harbor.
The key challenge with a traditional cold frame is to be present to prop open the lid on a sunny winter day. Even on the coldest day, the “greenhouse effect” results in temperatures high enough to damage or kill the plants growing inside. Since the Battery Rooftop Gardener is not present to perform this task, the cold frame has been designed with automatic pistons, which sense the interior temperature and then automatically lift the heavy lid to allow ventilation. As you can can see from the photograph below, this is a major piece of engineering:
Although the late delivery of the cold frame has not permitted a mid-winter crop, Melissa did sow spinach and lettuce mix on December 31. As an experiment, she watered the sowed seeds with snow instead of liquid water. As of January 6, still no germination, so Melissa re-sowed. This time we are going to be more diligent about watering, and we have adjusted the heating pad to ensure a bit more warmth on cloudy days and at night. My instructions from Annie are to water so that the soil is the consistency of “the inside of a just baked cookie.” Will report further on success — or lack of it — in germination, and would be grateful to hear from other New Yorkers experienced with roof-top cold frames.