Mature size & growth rate

How big does Red Cabbage (Brassica oleracea var. capitata f. rubra 'Red Drumhead') get?

Also called red cabbage, purple cabbage.

More about red cabbage

About Red Cabbage

Brassica oleracea var. capitata f. rubra 'Red Drumhead' · also called red cabbage, purple cabbage · edible

Red cabbage is a firm-headed cabbage with dense, deep-purple, anthocyanin-rich leaves storing well after harvest. It needs a long season in full sun and firm, fertile, alkaline-leaning soil with steady moisture. Net against cabbage pests, feed generously, and harvest the solid heads in autumn; many keep for weeks in cool storage.

Mature size: 30-45 cm tall and wide; heads 15-25 cm across, 1-2.5 kg

Watch for — Clubroot: Swollen, galled roots stunt plants in acidic, waterlogged soil. Lime to raise pH, improve drainage, rotate widely, and dispose of infected roots away from the compost heap.

Indoor size vs how big it gets in the wild

Red Cabbage reaches its full size within one growing season — there is no "long-term" size, just how big it gets before you harvest or it dies back. Indoors and in a pot, expect 30-45 cm tall and wide. In the ground with no restriction it is a completely different plant — heads 15-25 cm across, 1-2.5 kg — which is why the pot, the light and the pruning matter so much for the size you actually end up with.

It sizes up fast and once, racing from seedling to full size in a single season; after cropping it is finished, so size is a within-season question.

Growth rate and years to mature

Red Cabbage is a fast grower. Realistically, expect a single growing season — it reaches full size in one year, then is done. Its feeding profile backs this up: a heavy feeder over a long season. base-dress with compost or balanced fertiliser and side-dress with nitrogen once or twice during leafy growth. reduce nitrogen as heads firm to keep them dense and storable rather than soft.

Want this turned into the right next pot at the right moment? The pot size calculator and the red cabbage repotting guide cover when and how much to size up — pot size is one of the biggest levers on how fast red cabbage grows.

How to keep red cabbage smaller

You are not stuck with the maximum size. For red cabbage specifically, these are the levers, in order of impact:

Choose a compact or dwarf variety of red cabbage from the start — that is the most reliable size control for an annual.
Grow it in a smaller container to naturally limit how large it gets.
For some crops, pinching or pruning the growing tips keeps the plant shorter and bushier.
Sow a little later or space plants closer if you specifically want smaller individual plants.

How to grow red cabbage bigger or faster

If you want it to fill the space sooner, push the conditions rather than hoping — for red cabbage the accelerators are:

Full sun, warm soil and steady water are what drive a crop to full size fastest.
Sow at the right time for your zone so it gets the whole season to size up.
Feed appropriately for the crop and never let it check (stall) from drought or cold.

Light is almost always the ceiling. The red cabbage light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When red cabbage outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for red cabbage:

It sprawls beyond its bed or container before harvest — usually a spacing or support issue.
It flops or needs staking once it hits full height.
Once it has fruited or bolted, it is at its final size for good — the next plant is a new sowing.

If it is the pot rather than the room, it is a repotting job, not a goodbye — see the red cabbage repotting guide. If you want more of this plant instead of a bigger one, the red cabbage propagation guide turns prunings into new plants.

Red Cabbage size — frequently asked questions

How big does red cabbage get?

Red Cabbage reaches 30-45 cm tall and wide when grown indoors, and far larger where it grows unrestricted (heads 15-25 cm across, 1-2.5 kg). It sizes up fast and once, racing from seedling to full size in a single season; after cropping it is finished, so size is a within-season question.

Is red cabbage slow or fast growing?

Red Cabbage is a fast grower. Expect a single growing season — it reaches full size in one year, then is done. Red Cabbage reaches its full size within one growing season — there is no "long-term" size, just how big it gets before you harvest or it dies back.

How long does red cabbage take to reach full size?

Roughly a single growing season — it reaches full size in one year, then is done. Light, pot size and feeding move that timeline more than anything else.

How do I keep red cabbage smaller?

Choose a compact or dwarf variety of red cabbage from the start — that is the most reliable size control for an annual. Grow it in a smaller container to naturally limit how large it gets. For some crops, pinching or pruning the growing tips keeps the plant shorter and bushier. Sow a little later or space plants closer if you specifically want smaller individual plants.

How can I make red cabbage grow bigger or faster?

Full sun, warm soil and steady water are what drive a crop to full size fastest. Sow at the right time for your zone so it gets the whole season to size up. Feed appropriately for the crop and never let it check (stall) from drought or cold.