Heirloom / Open Pollinated Spinach is daylight sensitive, doing best in cool, mild climates. Direct sow Heirloom / Open Pollinated Spinach Seeds in very early spring or late fall, in full sun or partial shade, covering with ½” of soil. Germination usually occurs in 6-15 days when the temperature ranges from 55-70°. Thin Heirloom / Open Pollinated Radish plants to 3″ for food and seed saving.