Where broccoli and cauliflower reward you with a narrow, urgent harvest window, summer cabbage is far more forgiving -- both in the ground and, unusually for a brassica, after you've cut it. A solid head keeps for weeks in cool storage rather than days, and cabbage is one of the very few vegetables that turns into a genuinely long-life, no-refrigeration-needed food through fermentation. That combination -- reliable yield, real storage life, and a preservation method that needs nothing but salt -- makes it one of the more useful brassicas for a household planning past a single season.
Water need
Consistency matters more than total volume -- a dry spell followed by heavy rain or watering once heads are near full size is the classic cause of split heads.
Calories at a glance
250 kcal/kg -- low compared to calorie staples like potatoes or dried beans (scale is log-based across all 55 crops in the calculator, staples included, so vegetables don't all bunch at the bottom).
Temperature Range by Month
Month on the bottom, temperature up the side. The pale green background is what the plant can survive at all -- fatal above or below it, labelled directly on the chart where that applies to your zone. The coral band is its ideal range, and only fades in during the months this zone would actually have the crop in the ground -- reusing the exact same sowing/harvesting data as the calendar further down the page. The blue line is real monthly climate data (not a modelled estimate) for a representative rural/agricultural location in this zone -- a small farming town or agricultural research station rather than a major city, to avoid the warmer bias city weather stations have. For the actual verdict on how well this crop does in your zone, see the badge at the top of the page -- that's based on the site's own researched yield figures, not this chart.
Quick Start: Sowing to Harvest
- Sow. Sow Feb-Apr for a summer harvest, though exact timing varies significantly by zone -- check the calendar below. Cabbage germinates readily in cool soil.
- Transplant & space. Move seedlings out once well-rooted, giving plants about 45cm (18in) of space. Protect young transplants from slugs, which find them especially attractive.
- Tend through the season. Keep moisture level and consistent, especially as the head fills out -- a dry spell followed by heavy watering or rain is the classic cause of split heads once they're near full size.
- Harvest. Cut when the head feels solid and dense under a light squeeze, not spongy -- typically 10-16 weeks after sowing depending on variety and climate. If you can't harvest right away, a partial twist of a mature head can slow water uptake and buy a little time before it splits.
Sowing & Harvesting Calendar
Pick your zone under "Temperature Range by Month" above and this updates too. The Sow row: green is the normal safe sowing window, amber is pushing the season by roughly a month either side with basic outdoor protection (cold frame, fleece, cloche), blue is starting seed indoors or under glass for an even earlier transplant. The Harvest row shows the head-forming window -- like broccoli and cauliflower, summer cabbage is a one-shot harvest per plant with no extended "still pickable" tail in the ground; its real staying power shows up after harvest instead (see Storage & Preservation below).
Calories & Yield
Cabbage is a nutrition and storage crop, not a calorie staple -- about 250 kcal per kg, similar to cauliflower and well below true calorie staples. Grow it for variety, vitamin C, and its unusual ability to actually keep once cut.
| Climate Zone | Yield per plant | Calories per plant | Viability |
|---|---|---|---|
| Tropical / Humid | 0.8 kg | 200 kcal | Viable |
| Subtropical | 1.0 kg | 250 kcal | Viable |
| Mediterranean | 1.0 kg | 250 kcal | Viable |
| Temperate Maritime | 1.0 kg | 250 kcal | Viable |
| Temperate Continental | 1.0 kg | 250 kcal | Viable |
| Cool / Boreal | 0.6 kg | 150 kcal | Viable |
| Arid / Semi-Arid | 0.18 kg | 45 kcal | Viable -- challenging (60% yield) |
| Highland / Alpine | 0.5 kg | 125 kcal | Viable |
Figures per plant sown, from the site's own crop database. Arid-zone figures already include the 60% yield penalty the calculator applies to "challenging" growing seasons there. Subtropical, Mediterranean, Maritime and Continental all tie for the highest yield -- the crop database calls summer cabbage "very reliable" generally rather than singling out one zone.
Varieties Worth Knowing
Summer cabbage varieties mainly differ in speed to maturity and head shape. All the varieties below are open-pollinated (OP), meaning seed saved from them breeds true and is worth keeping under this site's seed-saving approach; none are F1 hybrids.
Seed Saving -- Quick Guide
Summer cabbage crosses freely with kale, broccoli, cauliflower, Brussels sprouts, kohlrabi and other cabbages -- all one species (Brassica oleracea). It's biennial, so saving true seed takes a two-year cycle.
SERVINGS, NOT DAILY CALORIES This works out plate-sized servings of summer cabbage from your seed during its fresh harvest window only, not your group's full daily calorie needs. For that, use the main calculator.
BIENNIAL Summer cabbage is a biennial, not an annual -- it doesn't produce seed in its first year. Plants grow through year one, a few overwintered plants flower and set seed in year two, and that seed is only ready to sow in year three. If you're starting from scratch with no ongoing seed supply, that means having enough seed on hand for both year one's and year two's sowing up front. Plan for roughly double the seed quantity below if that's your situation.
Estimated for your selected zone above, using this site's own germination, loss and yield figures for summer cabbage -- a helping is roughly what you'd put on a plate as part of a meal with other veg. Treat it as a planning estimate, not a promise.
Storage & Preservation
Cabbage is notably more forgiving after harvest than its brassica relatives -- a solid head keeps about 3-4 weeks in cool conditions (a cellar, unheated garage, or fridge), far better than broccoli or cauliflower, which barely keep at all.
For real long-term preservation, cabbage has a standout option most brassicas don't: fermentation. Sauerkraut needs nothing but shredded cabbage, salt, and time, and once properly fermented it keeps for months without refrigeration -- a genuinely useful, low-input, long-shelf-life food. It can also be blanched and frozen, though the texture suffers more than fermenting or pickling does.
Growing Cabbage Without Bought Inputs
Cabbage shares the same pest profile as the rest of the brassica family -- cabbage white caterpillars, flea beetle, aphids -- and exactly which one causes trouble depends heavily on where you are. What works almost everywhere instead:
Floating row covers or fine insect netting are the single most effective input-free defence -- they physically exclude the large majority of common brassica pests regardless of which one is active locally, with no identification needed.
Companion planting helps too: aromatic herbs like dill, oregano or thyme interplanted nearby mask the scent brassica pests use to find their host, and nasturtiums nearby often draw pests away as a sacrificial trap crop.
Crop rotation matters as much as pest defence -- avoid growing cabbage, or any brassica, in the same bed two years running. This breaks the life cycle of soil-borne problems like clubroot, which can persist in soil for years without a host to reset the clock.
Slug defence for young transplants is cabbage's biggest zero-input concern specifically -- beer traps, a barrier of crushed eggshell or grit around each plant, or simply hand-checking at dusk when slugs are most active can save a whole tray of seedlings.
Frequently Asked Questions
Do I need to do anything special to get a cabbage head to flower for seed?
Yes -- a tight cabbage head is often too dense for the flower stalk to push through on its own the following spring. Cut a shallow cross into the top of the head (an inch or two deep) before it overwinters, which gives the stalk a route out without killing the plant.
Can I save cabbage seed if I'm also growing broccoli or kale?
Only carefully. Cabbage can cross-pollinate with kale (oleracea-type), broccoli, cauliflower, winter/Savoy cabbage, Brussels sprouts, kohlrabi and purple sprouting broccoli if more than one is left to flower nearby at the same time. Keep varieties about half a mile (800m) apart for home use, or only let one flower per season.
How much heat and cold can summer cabbage survive?
Roughly -4°C to 27°C (25°F to 80°F), but summer varieties are bred for faster maturity in warmer conditions and are notably less cold-hardy than winter or Savoy types -- don't assume the same frost tolerance across every cabbage in the garden.
Why did my cabbage head split?
Almost always a moisture swing -- a dry spell followed by heavy rain or a big watering once the head is near full size causes it to take up water faster than the outer leaves can stretch to accommodate, and it splits. Keeping moisture level and consistent as heads near maturity is the main defence.
How long does cabbage keep after picking?
About 3-4 weeks in cool conditions (a cellar, unheated garage, or fridge) -- notably better than broccoli or cauliflower, which barely keep at all. For much longer storage without refrigeration, ferment it into sauerkraut.
Is cabbage a good calorie crop for self-sufficiency?
No -- cabbage provides about 250 kcal per kg, similar to cauliflower and well below calorie staples like potatoes or dried beans. Grow it for variety, vitamin C, and its unusually good storage and fermentation potential, not calories.
How long does cabbage seed stay viable?
Around 4-5 years if kept cool, dark and dry, similar to other Brassica oleracea seed, though germination rates decline gradually each year even within that window. Test old seed before relying on it for a full planting.
Do I need pesticides to grow cabbage?
No. Floating row covers or fine insect netting physically exclude most common brassica pests without needing to identify which one you're dealing with, and companion planting, crop rotation and hand-picking cover the rest for a home-scale planting.