When to plant spinach in Longview and Kelso, WA

Why spinach bolts

Spinach is a long-day plant: once the days get longer than about 14 hours, it starts making flowers instead of leaves. In Portland and Seattle that happens around late April, and warm weather speeds it up. That's why spring spinach has a short window, and why fall and overwintered crops are often the best ones here.

Sow as early in spring as the soil can be worked, choose slow-bolting varieties, and harvest whole plants once they start to stretch upward.

Germination and temperature

Spinach sprouts in soil as cool as 35 to 45°F, best around 70°F, and very poorly above about 85°F. For a fall crop, sow in late summer once the soil has cooled, or water and shade the seedbed to keep it cool. Established plants are very cold hardy, surviving temperatures into the teens with some cover, and fall-sown spinach often grows again in February west of the Cascades.

Soil pH matters more than for most greens

Spinach is unusually sensitive to acidic soil. Below a pH of about 6.0, seedlings tend to grow slowly and turn yellow. It grows best at a pH of 6.5 to 7.5. Many west-side soils are acidic, so if spinach has struggled before, test the soil and add lime as needed. It also likes plenty of nitrogen and steady moisture.

Pests and diseases

Downy mildew causes yellow patches on top of leaves with grayish-purple fuzz underneath, especially in cool, damp weather. Many newer varieties are bred to resist it. Leaf miners tunnel through leaves; row cover keeps the flies out. And slugs love young spinach.

Harvest and storage

Pick outer leaves once plants have five or six, or cut the whole plant an inch above the soil and let it regrow. Spinach keeps best near freezing with high humidity, bagged in the fridge, where it lasts about 10 to 14 days.