(Image from: https://hudsonvalleyseed.com/products/abundant-bloomsdale-spinach?_pos=1&_psq=abundant%20&_ss=e&_v=1.0)
Growing Instructions for Abundant Bloomsdale Spinach:
Direct sow any time soil can be worked in the cooler months, from about 6 weeks before first fall frost until the date of your last spring frost. Broadcast seeds in a well cultivated garden patch, or seed in rows 10" apart, and thin seedlings to 6". Spinach sown in fall will come up extremely early in the spring. When full size, harvest the entire plant promptly, especially in late spring, when it tends to bolt under heat pressure. Sow in successions for a steady crop. For a good fall crop, sow spinach in August. Fall crops yield until deep winter; with a cold frame, you can eat spinach all winter long.
(from Hudson Valley Seed Company website)