Spinach

Spinach can be one of the easiest crops to grow depending on the gardener’s choice of planting times. It is fast-growing, short-lived, heat-sensitive, and dependent on adequate fertility. By fortifying soil and avoiding high temperatures in summer, gardeners can enjoy several months of satisfying harvests.

Spinach Selections

  • Savoy spinach types have crisp, crinkly leaves and a firm texture.
  • Semi-savoy varieties are less crinkly and preferred by some for ease of cleaning.
  • Flat-leaf types have large, smooth, and more tender leaves than curly varieties.
  • Baby spinach involves harvesting immature leaves of any variety.
  • Some varieties perform differently when grown in spring or fall. Check seed packet and catalog descriptions for disease-resistant varieties, their tolerance of light frost and overwintering in mild microclimates, and any tendency to bolt, that is go to seed quickly, as spring warms up.
  • Malabar spinach is not a true spinach but shares the common name. It has leaves with a mucilaginous texture on a tropical perennial vine that grows in the warm season.
  • New Zealand spinach, of yet a different species, has fuzzy, succulent leaves, tolerates heat, and spreads in clumps. It also is not a true spinach.

Sowing and Growing

  • Amend seed bed with compost or aged manure for rich, fertile, well-drained soil.
  • Refrigerate seed one week before planting to encourage germination, particularly when planting in late summer.
  • Direct sow February-April after soil temperature reaches 50 degrees to grow during cool spring months with short days. Start seed indoors if soil is too cold or soggy from winter rains.
  • Plant again August-September as day length shortens for a fall crop. In a succession garden, some light shade from taller plants may be needed during late summer heat waves.
  • Sprinkle seed in beds over a 2-4 in. wide band, 12-15 seeds per row about ½ in. deep, and cover lightly with soil.
  • Thin to 3-4 in. apart or transplant starts when seedlings are 2 in. high. Snip thinnings at soil level to avoid disturbing roots of remaining seedlings.
  • Use loose, fast-draining potting mix at least 8 in. deep when planting in containers.
  • Repeat sowing every 2-3 weeks for a continuous harvest. Most varieties mature in 40-50 days.
  • Side dress spinach mid-season with compost, blood meal or kelp. Nitrogen-rich amendments encourage fast, tender growth.
  • Keep soil evenly moist with regular watering; spread mulch over beds to discourage weeds.

Harvesting

  • Harvest when leaves reach 4-6 in. long on plants that have developed at least 8 leaves.
  • Cut an entire plant at the base or break off outer leaves at the base of their stems in a cut-and-come-again method to allow for additional harvests.
  • Do not wait too long to harvest spinach or larger leaves will become bitter and plants may bolt.
  • Allow fall plantings to continue growing to maturity in cold weather that brings a moderate frost. Spinach can tolerate brief temperature drops to 20 degrees but benefits from a row cover in sustained lows. Growth may slow or stop before resuming when temperatures rise.  

Check for Pests

  • Check for pale-colored burrows inside thin leaves indicating leaf miners. Crush any eggs on leaf undersides and destroy severely damaged leaves.
  • Cover young seedlings with spun row covers to deter damage from birds.
  • Hand pick pests such as looper worms, slugs and snails; hose off aphids.
  • Expect fewer pests in a fall-winter garden.

Additional Information

February 2022

Source URL: https://class.ucanr.edu/site/uc-master-gardener-program-sonoma-county/spinach