Types and days to harvest
Kale is Brassica oleracea, Acephala Group, usually a biennial grown from seed (Wikipedia). Leaf types are curly (Scots, blue curled), bumpy (lacinato, also called Tuscan or dinosaur kale) and plain or flat (Red Russian, White Russian).
| Variety | Leaf | Days | Named by |
|---|---|---|---|
| Red Russian | Flat, purple | 50 | USU, NC State |
| Improved Dwarf Siberian | "Very cold tolerant" | 50 | NC State |
| Starbor | Curly, green | 55 | USU |
| Scarlet | Red leaf | 55 | USU |
| Redbor (hybrid) | Curly, red | 55 | NC State |
| Dwarf Blue Curled Vates | Low, curly, blue-green | 55 | Delaware |
| Winterbor | Curly, blue-green | 60 | Delaware |
| Toscano / Lacinato | Bumpy, blue-green; tolerates heat and cold (NC State) | 65 (NC State); 65–80 (Delaware) | NC State, Delaware |
Baby leaves are ready 20–30 days after seeding and mature leaves 50–75 days (NC State).
Spring and fall timing
| Step | Figures given |
|---|---|
| Start transplants | 4–6 weeks from seed to transplant (UNH); about 4 weeks (UMN); 5–6 weeks to reach 4–6 mature leaves (USU) |
| Spring planting | Set out 4 weeks before the last frost (UNH, NC State) or 4–5 weeks (USU); direct-sow as soon as the soil can be worked (UMN) |
| Spring harvest | Pick before hot, dry weather (UMN); kale grows best when temperatures do not exceed 75°F (USU) |
| Fall planting | Direct-seed about three months before the average fall frost, or start transplants indoors in June (UMN); plant six weeks before the first fall frost (NC State); plant early cultivars 50–75 days before the planned harvest, aimed at 2–3 weeks after the first frost (USU) |
| Fall sowing in New Hampshire | Late July through August suits many fall vegetables; first freezes come in early to mid-October in central and southern NH and mid to late September in the north (UNH) |
To count back, start from the average first fall frost and the days to maturity, which run from germination, not sowing (UNH). Find your dates on frost dates explained or the planting calendar.
- 1. Start transplants 4–6 weeks ahead (UNH); set out 4 weeks (UNH, NC State) or 4–5 weeks (USU) before the last spring frost
- 2. Imported cabbageworm adults appear in May (UNH) or mid-May (UMN); cover plants at planting
- 3. Harvest spring kale before hot, dry weather (UMN); best growth at or below 75°F (USU)
- 4. Fall crop: direct-seed about 3 months before the first frost (UMN) or plant 6 weeks before it (NC State); late July to August in New Hampshire (UNH)
- 5. Cabbage loopers fly in from mid-July, often not until mid to late August (UNH); early July to late August in Minnesota (UMN)
- 6. Frost sweetens fall kale (USU, NC State); young plants take 25°F (USU) and kale survives about 20°F (UMN)
Cold, heat and flavor
- Kale stands hard frost (UNH), keeps producing after the first fall frosts (UMN) and can stay in the garden through winter (USU).
- Frost improves the flavor of fall kale (USU, NC State).
- Heat or water stress makes leaves bitter or pungent (UMN) and tough (USU).
Containers and small beds
- Pot size: at least 3 gallons and 8 in deep, plants 6 in apart (NC State Extension Gardener Handbook). University of Maryland does not name kale, but puts cole crops in its medium class of 4–6 gallons, 8–12 in deep. See container sizes for vegetables.
- Light: full sun to part shade; light shade helps in hot weather (Delaware).
- Baby leaves: plants can stand as close as 4 in in the row (UMN).
- Grid beds: 1 plant per square foot (UF/IFAS) or 2 at 8-in spacing (NC State); compare all crops on square foot gardening spacing.
| Source | In the row | Between rows | Seed depth |
|---|---|---|---|
| UMN | Thin to 8–12 in; transplants 8 in | 18–30 in (transplants 18 in) | 1/4–1/2 in |
| USU | 12 in (summary: 12–18 in) | 2 ft | 1/4–1/2 in |
| NC State | Sow 1 in apart, thin to 1 ft; transplants 6 in | 2–3 ft | 1/2 in |
| UNH | 12–18 in | — | — |
Water, soil and harvest
- About 1 inch of water a week, more on sandy soil (UMN); 1–2 inches, deep and infrequent, with drip and mulch (USU).
- Soil pH 6.0–7.5 (UMN, NC State); test the soil first (UMN, USU). Mulch 3–4 in deep (UMN) or 2–3 in of straw (NC State).
- Pick outer leaves and let the center keep growing (NC State, USU), or cut the whole plant (UMN).
- Storage: 2–3 weeks at 32°F and 95% humidity (USU); up to one week in a home refrigerator (NC State).
Cabbage pests
| Pest | Signs | Extension guidance |
|---|---|---|
| Imported cabbageworm | Velvety green larvae; irregular holes and droppings. White "cabbage white" butterflies (UNH) | 3–4 generations a year in NH (UNH), 3–5 in MN (UMN). Kale is less susceptible than cabbage, collards or broccoli (UNH) |
| Cabbage looper | Smooth green larvae up to 2 in that move in a loop; large ragged holes (UNH) | Migrates north; does not overwinter in New England or the upper Midwest (UNH, UMN). Inspect transplants; row covers if it is a yearly pest (UNH) |
| Diamondback moth | Larvae under 1/2 in that wriggle and drop on silk; "windowpane" feeding (UNH) | Often worse in dry years; highly resistant to insecticides (UNH) |
| Flea beetles | Small holes in leaves; seedlings most at risk (UMN) | Row covers secured on all sides before beetles arrive; planting brassicas in mid to late July shortens the feeding window in Washington (WSU) |
| Cabbage maggot | Root feeding that can kill plants (UMN) | Radish trap crop (see below) |
| Swede midge | Distorted, stunted plants; favors Red Russian types (UMN) | Rotate: no cole crops in the same spot for four years (UMN) |
| Aphids, harlequin bug | Listed by USU and Delaware | Strong water spray or insecticidal soap for aphids (USU) |
- Cover at planting. Lightweight row cover over seedlings or transplants keeps moths from laying eggs; leave it until harvest (UMN). UNH buries the edges, avoids covers on summer brassicas, and does not cover unrotated ground where overwintered pests could be trapped underneath.
- Check weekly on both sides of the leaves (UMN) and hand-pick caterpillars into soapy water (UMN).
- Clean up. Destroy crop residue and mustard-family weeds such as wild mustard and shepherd's purse (UMN, UNH).
- Protect natural enemies such as parasitoid wasps (UMN), with flowering borders like sweet alyssum or buckwheat (UNH).
- If spraying. Bacillus thuringiensis (Bt) works best on small caterpillars and spares natural enemies (UMN, UNH). Follow the product label.
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.
Trap crops
A trap crop is a planting the pest prefers, set out so insects gather on it instead of the main crop.
| Trap crop | Pest | What the source reports |
|---|---|---|
| Pacific Gold mustard, Dwarf Essex rape and pac choi, mixed | Crucifer flea beetle | Protected broccoli in WSU work. Plant before the main crop, at about 10% of the crop area; may not fully protect during heavy infestations (WSU PNW640) |
| Radish, intercropped | Flea beetles, cabbage and root maggots | Draws them from cabbage-family plants (WSU Skagit County Master Gardener column) |
| Mustard, intercropped | Cabbageworms | Attracts them in cabbage (same column) |
| Collards, as a border | Diamondback moth, imported cabbageworm | Two border rows kept diamondback moth below thresholds in nine Florida cabbage fields; Massachusetts trials found 25% fewer cabbageworm larvae (UVM) |
Check trap crops often and remove the insects or infested plants, or pests keep breeding there; strong fliers can skip a border (WSU column). The collard results come from commercial fields; none of these sources measured a small bed.
Where sources disagree
| Question | Figures given |
|---|---|
| Spring set-out | 4 weeks before the last frost (UNH, NC State) vs 4–5 weeks (USU) vs as soon as the soil is workable (UMN) |
| Fall planting | About 3 months before the first frost (UMN) vs 6 weeks (NC State) vs 50–75 days before a harvest 2–3 weeks after frost (USU) |
| Cold limit | Young plants 25°F (USU) vs about 20°F (UMN) |
| Days to maturity | 40–65 (UMN fall table); 55–70 (UNH fall chart); 50–75 (NC State) |
| Plant spacing | 8–12 in (UMN) vs 12–18 in (UNH, USU summary) vs 1 ft (NC State); 6 in in containers (NC State handbook) |
| Square foot count | 1 per square (UF/IFAS) vs 2 (NC State) |
| Row cover in summer | Leave on until harvest (UMN) vs not on summer brassicas (UNH) |
Small-space checklist
- Set out transplants about 4 weeks before the last spring frost; harvest before summer heat.
- Sow or transplant the fall crop in midsummer, counted back from the first fall frost.
- Pots of 3 gallons or more and 8 in deep, plants 6 in apart; 1–2 per square foot in grid beds.
- Row cover at planting, edges buried; check both leaf sides weekly.
- Leave fall kale through frost for sweeter leaves.
More crop pages: spinach, lettuce, tomatoes and peppers.
Sources
- University of New Hampshire Extension — Growing Vegetables: When to Plant Your Vegetable Garden (fact sheet)
- University of New Hampshire Extension — Fall Vegetable Gardening (Yard and Garden Infoline, 2020)
- University of New Hampshire Extension — Cool Season Vegetables (Will Lowenthal, 2019)
- University of New Hampshire Extension — Caterpillar Pests of Brassica Crops in New Hampshire (2025)
- University of New Hampshire Extension — Cabbage Looper (fact sheet, 2018)
- University of Minnesota Extension — Growing collards and kale in home gardens
- University of Minnesota Extension — Planting vegetables in midsummer for fall harvest
- University of Minnesota Extension — Caterpillars on cole crops (Schuh, Hahn and Wold-Burkness, reviewed 2022)
- Utah State University Extension — How to Grow Kale in Your Garden (Drost and Johnson, 2020)
- NC State Extension — Kale
- NC State Extension Gardener Handbook — Chapter 18, Plants Grown in Containers (Table 18-1)
- University of Delaware Cooperative Extension — Kale (fact sheet, 2024)
- Washington State University Extension — Organic Management of Flea Beetles (PNW640, Parker, Miles, Murray and Snyder, 2012)
- Washington State University Extension — Trap Cropping (PDF)
- University of Vermont Extension — Perimeter Trap Cropping: A Novel Approach to Insect Pest Control (Vern Grubinger, 2004)
- University of Maryland Extension — Types of Containers for Growing Vegetables
- UF/IFAS Gardening Solutions — Square Foot Gardening
- NC State Plants for Human Health Institute — Square Foot Seeds (PDF)
- Wikipedia — Kale (secondary source)
All sources were opened and checked in October 2026. Rules and figures change; confirm with the original before acting.