55-70 Days to maturity. Brassica oleracea ’Subzero’. Subzero Kale Cover Crop Seeds. Non-GMO, Annual, Hybrid. This is an outstanding hybrid kale variety with excellent cold tolerance and foraging qualities for wildlife and cattle. Subzero Kale, as the name suggests, is ideal for colder seasons and regions. It thrives when planted in spring, fall, or even mild winter climates. The lush green foliage is beautiful to look at and offers vital nutrients to humans, animals, and the environment. We offer bulk options as well for all those large pastures and farms.~8,000 seeds/oz.