Types and days to harvest
| Type | Leaf | Examples named |
|---|---|---|
| Savoy | Crinkly, curly; keeps longer (CSU). Soil and sand collect in the crinkles (UMD). | Whale (Clemson) |
| Semi-savoy | A hybrid of flat and savoy types (CSU); most spinach grown in South Carolina (Clemson) | Avon, Regal (UW) |
| Smooth (flat) | Quick, high-yielding, easy to clean; usually grown for canning and freezing (CSU) | Olympia, Space (UW) |
Days to harvest: 40 (Colorado State GardenNotes #720), 28–55 from seed (UMD), 40–60 (Montana State), 37–45 (Clemson), or 40–50 in good conditions but 60–70 for very early plantings (UMass). Not true spinach: New Zealand spinach prefers hot weather and Malabar spinach is a vine for summer; "perpetual spinach" is actually a chard (UMD).
Cool-season timing
| Step | Figures given |
|---|---|
| Cold tolerance | "Hardy," growing in days as cool as 40°F (CSU #720); withstands heavy spring and fall frosts (UMD); see the disagreement table for low-temperature limits |
| Spring sowing | 2–3 weeks before the last frost (USU); 2–4 (CSU #720); about 4 (CSU FoodSmart, UW); 4–8 (Penn State); window opens 6 weeks before (Montana State); as soon as the soil can be worked (UMass, Illinois) |
| Soil temperature | Sow once soil reaches 40°F (USU) or 45°F (UMD) |
| Best weather | 50–60°F (CSU, UW, Penn State); 55–60°F (UMass); 50–63°F (Oregon State) |
| Succession | About every 2 weeks (UW); several small plantings a few days apart (UMD) |
| Fall sowing | 6–8 weeks before the first fall frost (Penn State, Montana State); about 6 weeks (UMass); mid-August in Wisconsin (UW) |
| South Carolina | Spring: Mar 15–Apr 15 Piedmont, Feb 1–Apr 1 Coastal Plain. Fall: Aug 1–Sep 30 and Aug 15–Oct 15 (Clemson) |
Look up your dates on frost dates explained; the planting calendar uses Montana State's spinach window.
Day length and bolting
Bolting means sending up a seed stem; the leaves turn bitter (Penn State, CSU). Spinach is day-length sensitive and bolts in June even in cool weather, so spring plantings usually stop producing by the end of May in Pennsylvania (Penn State). Illinois says spinach bolts quickly in long days and warm temperatures speed it up.
UMass gives about 12 hours as the optimum day length. None of the extension pages consulted gives a bolting threshold in hours. A HortScience study of one cultivar, 'Dimple', found the critical day length for bolting to be longer than 13 hours and shorter than 15 hours, and transplants raised under shorter days formed shorter flower stalks (Chun et al., 2000).
| Trigger | What sources say |
|---|---|
| Long days | Bolting occurs as days get longer (Delaware, UMD, USU, Oregon State) |
| Heat | Temperatures reaching 80°F trigger it (Penn State); above 75°F adds bitterness (USU); high temperatures accelerate it (Delaware) |
| Dry soil | Drying out triggers it (Penn State); falling soil moisture or nutrients raise the risk (Oregon State) |
| Crowding | Unthinned plants bolt early (Penn State); density raises the risk (Oregon State); close spacing can encourage it (UMD) |
| Cold on young plants | Exposing young plants to 40–60°F increases bolting (Oregon State) |
- 1. Spring sowing 2 to 8 weeks before the last frost, depending on source (USU, CSU, Penn State)
- 2. Best growth in 50–60°F weather (CSU, UW, Penn State)
- 3. Days near 12 hours are the optimum (UMass); one study put the bolting threshold between 13 and 15 hours (Chun et al., one cultivar)
- 4. Long days and heat bring bolting; Penn State names 80°F; New Zealand or Malabar spinach fill summer (UMD)
- 5. Fall sowing 6–8 weeks before the first fall frost (Penn State, Montana State); chill summer and fall seed 1–2 weeks first (Illinois)
- 6. Overwinter plants with 4–5 true leaves under heavy mulch (USU) or row cover (UMass)
Ways to hold bolting off, as the sources give them:
- Sow early so the crop matures before long days and heat (Clemson).
- For spring, choose slow-bolting, "long-standing" varieties (USU, Illinois, Delaware), such as Olympia, Tyee or Indian Summer (UW), or Bloomsdale or Whale (Clemson).
- Thin on time, to 4–6 in (Penn State), and keep the soil moist; mulch keeps it cool (Penn State, USU).
- Once temperatures reach 70°F, cover with shade cloth or floating row cover (Penn State).
- Harvest the whole crop when seed stalks begin to form (Illinois).
Sowing
- Depth. 1/2 inch; Colorado State, USU, Penn State, UW, Clemson and Illinois agree.
- Fresh seed. Germination declines quickly (Penn State); seed over a year old germinates poorly (Clemson).
- Emergence. 7–10 days (USU, Penn State); 6–14 (CSU #720).
- Late sowings. Above 80°F germination drops (USU); Illinois advises refrigerating seed 1–2 weeks before summer or fall sowings.
- Thinning. At 3–4 true leaves (USU) or about 2 in tall (Penn State, UW).
Containers and small beds
- Pot size: 1–3 gallons and 4–6 in deep (UMD), at least 2 gallons and 4–6 in deep (UW–Madison), 4–6 in deep for any variety (Montana State). See container sizes for vegetables. In beds, Penn State loosens soil 12–18 in deep for the long taproot.
- Mix: a nutrient-rich soilless mix (Penn State); commercial potting mix, filled to the top (UW–Madison).
- Light: at least 5 hours (Montana State); partial shade of 4–6 hours tolerated (UMD); container vegetables in general need at least 6 hours (UW–Madison).
| Source | In the row | Between rows / beds |
|---|---|---|
| USU | 3 in | 12 in |
| UMD | 3 in, thinned to about 6 in in early summer | Wide rows or beds |
| Colorado State | 4–6 in | — |
| Penn State | Sow 2 in, thin to 4–6 in | 12–18 in; 9 seeds per square foot |
| Illinois | Thin to 2–4 in | 12 in; 4–6 in each way in beds |
| Clemson | 2 in | 1–3 ft, or broadcast on 12-in beds |
Grid charts differ on spinach too: see square foot gardening spacing.
Water and feeding
- 1–2 inches of water a week (USU); water deeply enough to wet the top 6 in, in the morning (Clemson), at the soil rather than the leaves (Penn State).
- Soil pH 6.0–7.0; spinach is sensitive to acid soil (Clemson). Test the soil before fertilizing (USU, Clemson).
Harvest and storage
- Start: at six or more true leaves (UW) or a rosette of five or six leaves (Illinois).
- Leaf by leaf: pick outer leaves and leave the center rosette (Penn State); leaves 3–6 in long (Clemson).
- Whole plant: cut to within 2 in of the soil; it can regrow if the growing point is undamaged (USU).
- Storage: 32°F and 95% humidity for 1–2 weeks (USU) or 2–3 weeks (UMD); in a home refrigerator, use within 3–5 days (CSU FoodSmart).
Fall and winter
In South Carolina, spinach can be harvested through winter into spring (Clemson); in Maryland, protected fall crops last into December (UMD). Farther north, UMass suggests seeding in early September under floating row cover. USU overwinters plants that have 4–5 true leaves under heavy mulch, removed after the snow melts; UW cuts the leaves but leaves the roots and growing point. CSU covers immature plants with hay if the ground freezes.
Common problems
| Problem | Signs | Extension guidance |
|---|---|---|
| Leafminers | Mines inside leaves | Row covers exclude them (UMD); remove mined leaves; sprays fail once larvae are inside (UW) |
| Aphids | Curled leaves, insects underneath (USU) | They spread viruses (Clemson); strong water spray (USU, UW); more in the aphid guide |
| Slugs | Holes in leaves (USU) | Worst in very moist conditions (UW) |
| Flea beetles | Holes in seedlings (USU) | Floating row covers (USU) |
| Downy mildew, white rust | Listed by Clemson | Resistant varieties (Clemson, UW, Illinois) |
This page gives no pesticide or fertilizer rates. Follow your soil test and any product label exactly, and ask your county extension office to identify problems.
Where sources disagree
| Question | Figures given |
|---|---|
| Germination soil temperature | Min 40°F, optimum and max 70°F (CSU #720); best 55–65°F (USU); 45–68°F (Penn State); 32–60°F (UMass); 40–75°F (Montana State); optimum 70°F, inhibited above 85°F (Clemson) |
| Low-temperature limit | 25°F (CSU FoodSmart); 20°F without injury (Clemson); young plants 15–20°F (Penn State, UMass); young plants not seriously damaged down to 32°F (USU) |
| Heat limit | Best at or below 75°F, bitter above it (USU) vs bolting triggered at 80°F (Penn State) |
| Tyee leaf type | Savoy (UW) vs semi-savoy (Clemson, Delaware) |
| Mulch | Recommended (Penn State, USU) vs not around plants where slugs are a problem (UW) |
| Feeding | High nutrient needs (UMD) vs supplemental fertilizer usually unnecessary (Illinois) |
| Yield per 10-ft row | 4–6 lb (USU) vs about 2 lb (UMD) |
Small-space checklist
- Fresh, slow-bolting seed for spring; sown 1/2 in deep weeks before the last frost.
- Thin to 3–6 in and keep the soil evenly moist.
- Harvest spring spinach before long days and heat bring seed stalks.
- Re-sow 6–8 weeks before the first fall frost, with chilled seed.
- Pots of 2 gallons or more, 4–6 in deep, with at least 5 hours of sun.
More crop pages: lettuce, kale, tomatoes and peppers.
Sources
- Colorado State University Extension — Vegetable Planting Guide (CMG GardenNotes #720, reviewed 2024)
- Colorado State University Extension, FoodSmart Colorado — Colorado Spinach (reviewed 2025)
- Montana State University Extension — Can I Grow That Here? Vegetable Seed and Transplant Schedules (MontGuide)
- Utah State University Extension — How to Grow Spinach in Your Garden (Dan Drost, 2020)
- Penn State Extension — Growing Spinach, A Cool-Season Vegetable (Lew Palka, updated 2026)
- University of Maryland Extension — Growing Spinach in a Home Garden (updated 2023)
- University of Maryland Extension — Flower Stalks Form or Bolting of Vegetables (updated 2023)
- UMass Extension Vegetable Program — Spinach (fact sheet)
- University of Wisconsin–Madison, Wisconsin Master Gardener — Spinach, Spinacia oleracea (Susan Mahr, 2012, PDF)
- Oregon State University Department of Horticulture, Oregon Vegetables — Spinach (revised 2010)
- Clemson Cooperative Extension Home & Garden Information Center — Spinach (HGIC 1320, revised 2020)
- University of Illinois Extension — Spinach (Home Vegetable Gardening)
- University of Delaware Cooperative Extension, Weekly Crop Update — Bolting in Spring Planted Vegetables (Gordon Johnson, 2021)
- University of Delaware Cooperative Extension — Spinach (fact sheet)
- Chun et al. (2000), Bolting and Growth of Spinacia oleracea L. Can be Altered by Modifying the Photoperiod during Transplant Production, HortScience 35(4):624–626 (PDF)
- University of Maryland Extension — Types of Containers for Growing Vegetables
- University of Wisconsin–Madison Extension — Growing Vegetables in Containers
All sources were opened and checked in October 2026. Rules and figures change; confirm with the original before acting.
More in Crops & herbs
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Section overview: every page in this section.
- Lettuce
Spring and fall timing, succession sowing, heat and bolting, containers.
- Kale
Spring and fall timing, cold hardiness, containers, cabbage pests, row covers and trap crops.
- Radishes
Days to harvest by source, sowing temperatures, spacing, containers, flea beetles, root maggots and trap-crop use.
- Peas
Shelling, snow and snap types, early sowing and soil temperature, spacing, trellis heights, containers and the fall-crop question.
- Cilantro
Why it bolts in heat and long days, spring and fall sowing dates, re-sowing every 2–4 weeks, spacing, 1–3 gallon pots, leaf harvest and coriander seed.