All plants

Spinach

Spinacia oleracea

Chenopodiaceae · goosefoot family

Matures
40–50 days
Harvest
Over a period · Annual
Sun
4–8 hrs
Spacing
3–8 in
Botanical engraving of Spinach

Planting window

When to sow, by microclimate — foggier blocks run a different calendar than sunnier ones.

JanFebMarAprMayJun
Foggy●●●●●
Sunny●●●◐●
JulAugSepOctNovDec
Foggy●●●●◐◐
Sunny●●●●◐◐
Well-suitedMarginalNot suited

Sunlight

How well it does at each level of direct sun per day.

<2 hrsNot suited
2–4 hrsMarginal
4–6 hrsWell-suited
6–8 hrsWell-suited
8+ hrsMarginal
Well-suitedMarginalNot suited

Soil depth

Root room it needs — useful for sizing raised beds and containers.

6–10"Well-suited
10–15"Well-suited
15–18"Well-suited
18–24"Well-suited
Well-suitedMarginalNot suited

Spacing

Room each plant needs — along the row and between rows — for sizing beds.

In-row
3–8 in
Between rows
12 in

Growth habit

The shape it makes in the bed and how tall it gets — what tells you whether to give it a trellis, a stake, or just room.

Habit
Low mound
Mature height
6–12 in

Low and self-supporting — no staking needed.

How to start it

Sow it where it grows, or raise it under cover and set it out — and how far ahead to start the seedlings if it's the latter.

Usually
Direct-sow
Start indoors
4 weeks ahead
Direct-sowWell-suited
TransplantWell-suited

Sown straight into the bed it will grow in.

Well-suitedMarginalNot suited

Getting started

How it goes in the ground — how deep to sow or set it, and the soil temperature it needs to wake up. The cold-soil floor is the real limiter for direct-sowing in a foggy SF spring.

Started from
From seed
Ideal soil temp
65–75°F
Sow depth
0.5 in
Time to emerge
6–7 days

Germinates between 32–75°F; happiest around 65–75°F.

30°F110°F
IdealWorkable

Pests & diseases

What tends to trouble this crop — what it is, what you'll see, and what to do about it, least-toxic first.

Pests7

Aphids
What it is
Aphids have soft pear-shaped bodies with long legs and antennae and may be green, yellow, brown, red, or black depending on the species and the plants they feed on. A few species appear waxy or woolly due to the secretion of a waxy white or gray substance over their body surface.
What you'll see
Low to moderate numbers of leaf-feeding aphids aren't usually damaging in gardens or on trees. However, large populations can turn leaves yellow and stunt shoots; aphids can also produce large quantities of a sticky exudate known as honeydew, which often turns black with the growth of a sooty mold fungus.
What to do
Before planting vegetables, check surrounding areas for sources of aphids and remove these sources. On the other hand, these aphid-infested weeds can sometimes provide an early source of aphid natural enemies.
Source
Cutworms
What it is
Cutworms are dull brown caterpillars ranging in length from 1 to 2 inches when fully grown. They curl into a C-shape when disturbed.
What you'll see
Cutworms feed on blossoms and leaves of many ornamental plants and attack most garden crops. They clip off seedling stems near or just below the soil level.
What to do
Cutworms are pests mainly in the spring. Destroy crop residues; keep garden weed-free in winter.
Source
Earwigs
What it is
The adult earwig is readily identified by a pair of prominent appendages that resemble forceps at the tail end of its body. Used for defense, the forceps are somewhat curved in the male but straighter in the female.
What you'll see
European earwigs feed on a variety of dead and living organisms, including insects, mites, and growing shoots of plants. They are voracious feeders on soft-bodied insects such as aphids and insect eggs and can exert significant biological control under some circumstances.
What to do
Management of earwigs requires an integrated program that takes advantage of their habitat preferences. Initiate a regular trapping program.
Source
Flea Beetles
What it is
Their small size, enlarged back legs, characteristic shot-hole damage, and habit of jumping when disturbed make flea beetles easy to identify. There are numerous flea beetle species.
What you'll see
Adults feed mostly on leaves, leaving tiny pits or small holes at their feeding sites. Flea beetles feeding together can cover leaves with bleached, pitted areas or ragged holes.
What to do
Remove debris in the fall to remove any overwintering beetles. Reflective mulches applied very soon after planting and before plants become infected can be helpful.
Source
Loopers
What it is
Loopers are green caterpillars with several white stripes down their backs. They arch their backs as they crawl, this looping movement giving them their name.
What you'll see
Loopers eat irregular holes in leaves, most often older leaves. They may also bore holes in lettuce and cabbage heads or damage fruit.
What to do
Handpick. Apply Bacillus thuringiensis or spinosad; they are effective against loopers, especially when caterpillars are small.
Source
Snails and Slugs
What you'll see
Snails and slugs feed on a variety of living plants and on decaying plant matter. They create irregular holes with smooth edges on leaves and flowers by scraping with their rasp-like tongues.
What to do
It will not be possible to eliminate some shelters, such as low ledges on fences, the undersides of wooden decks, and water meter boxes, so make a regular practice of trapping and removing snails and slugs from these areas. The survivors congregate in the remaining shelters, where you can more easily locate and remove them.
Source
Vegetable Leafminers
What it is
Adult leafminers are small, active, black flies often with a prominent yellow triangle between the bases of the wings. The head behind the eyes is mostly black.
What you'll see
Leafminers attack many different vegetable and flower hosts, including cole crops, cucurbits, tomatoes, peas, beans, aster, begonia, dahlia, impatiens, lily, marigold, petunia, and verbena. Adult female leafminers puncture leaves and sometimes petals to feed on exuding sap.
What to do
Leafminers rarely require treatment in gardens. Clip off and remove older infested leaves.
Source

Diseases2

Downy Mildew on Spinach
What you'll see
Downy mildew causes light green to yellow angular spots on the upper surfaces of leaves. White fluffy growth of the fungus develops on the underside when moisture is present, but disappears soon after leaves dry.
What to do
The best way to prevent downy mildew is to avoid the environmental conditions that favor it. Use raised beds and avoid sprinkler irrigation.
Source
Spinach and Lettuce Virus Diseases
What you'll see
Beet western yellows, Curly top, Cucumber mosaic, Lettuce infectious yellows, and Lettuce mosaic Many viruses are difficult to distinguish from one another by symptom alone. In addition, for each particular disease, the symptoms will vary greatly depending on stage of plant at time of infection and other factors.
What to do
Buy and plant virus-free seed if available. Resistant varieties may be available.
Source

Sources

Every figure above is backed by these.