When to Sow: January-March; August–September Harvest: September-February crops can remain in the ground till needed.
Germination: 4-10 days Full Sun
Spinach is a cool-season crop and is best if sown in the spring or fall. (Sowing in soils with a temperature over 85°F (30°C) risks low or erratic germination.)
It grows happily in a wide range of soils, but it needs an alkaline soil (ideal pH is 6.5-7.5). Add lime well before planting if your soil tends towards the acidic. (Soils tests for pH are cheap, easy and invaluable for getting the best out of your cropping!)
In the spring, sow as soon as the ground can be worked, or start seeds indoors for an earlier crop. For a continual crop, continue with successive plantings every one or two weeks until your area's last expected frost. Spinach needs cool temperatures for best germination, so once longer days and warmer temperatures arrive, it’s best to wait until late summer or early fall for your next plantings.
Planting Tip: Even bolt-resistant varieties such as Red Kitten aren’t fond of intense sun. Planting in partial shade will help extend the growing season, or, in the spring, plant under a perennial that hasn’t yet leafed out. That way the spinach will get full sun in the Spring, but will then have partial shade once the perennial leafs out. Other options include planting on the north side of slower, taller crops.
Starting Indoors: Start seed as early as February, 2 seeds per module. Thin to the strongest plant once seedlings are 3cm tall. Transplant outside in March once two true leaves have formed and after hardening off.
Direct Seed: In the spring, sow as soon as the ground can be worked.
Baby leaf: Sow in a 2-4" wide band, 3/4" apart, about 40 seeds/ft.
Bunch Spinach: Sow spinach in traditional rows or broadcast seed within wide rows. For bunching and/or full size spinach, sow about 10 seeds per square foot or, at closest, at 1’ intervals. Keep rows 12-18” apart. Spinach likes its room and tends to bolt if overcrowded, so give the plants their space. The baby greens you thin will be super tasty in the kitchen.
Maintenance
Keep the soil consistently moist, as spinach has shallow roots and needs steady moisture to keep from bolting. Once plants reach 4” tall add 1-2” of mulch to keep soil cool, retain moisture and reduce weeds. Spinach does not need feeding in fertile, organic soil at proper pH.
Harvesting
For baby greens, harvest when leaves are 1-2” long. For bunch spinach, harvest when it reaches full size, but hasn’t yet bolted. Cut just below root attachment for "rooted spinach," or cut higher for "clipped spinach."
Triple-rinse leaves, as spinach is notorious for carrying grit in between its stems.
Companion Planting
Spinach does well with brassicas (brussels sprouts, kale, cabbage, broccoli, etc). Also likes alliums.