Mature size & growth rate

How big does Mizuna 'Red Kingdom' (Brassica rapa var. nipposinica 'Red Kingdom') get?

Also called Red mizuna, purple mizuna.

More about mizuna 'red kingdom'

About Mizuna 'Red Kingdom'

Brassica rapa var. nipposinica 'Red Kingdom' · also called Red mizuna, purple mizuna · edible

'Red Kingdom' is an F1 red mizuna with deeply serrated purple-red leaves on slim stems, adding colour and a mild mustard bite to salad mixes. Vigorous and slow to bolt, it holds its rich pigment best in cool weather and bright light, regrows well after cutting, and tolerates light frost, making it a standout baby-leaf and stir-fry green.

Mature size: About 20-30 cm (8-12 inches) tall and wide; harvested far smaller as baby leaf for salads.

Watch for — Slugs and snails: Shelter in the dense rosette and graze new growth in wet weather. Use barriers or traps and harvest in dry spells for clean leaves.

Indoor size vs how big it gets in the wild

Mizuna 'Red Kingdom' 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 about 20-30 cm (8-12 inches) tall and wide. In the ground with no restriction it is a completely different plant — harvested far smaller as baby leaf for salads. — 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

Mizuna 'Red Kingdom' 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: light feeder for fast leaves. compost-enriched soil plus a dilute balanced or nitrogen-leaning liquid feed every couple of weeks sustains vigorous, well-coloured regrowth.

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

How to keep mizuna 'red kingdom' smaller

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

Choose a compact or dwarf variety of mizuna 'red kingdom' 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 mizuna 'red kingdom' bigger or faster

If you want it to fill the space sooner, push the conditions rather than hoping — for mizuna 'red kingdom' 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 mizuna 'red kingdom' light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When mizuna 'red kingdom' outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for mizuna 'red kingdom':

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 mizuna 'red kingdom' repotting guide. If you want more of this plant instead of a bigger one, the mizuna 'red kingdom' propagation guide turns prunings into new plants.

Mizuna 'Red Kingdom' size — frequently asked questions

How big does mizuna 'red kingdom' get?

Mizuna 'Red Kingdom' reaches about 20-30 cm (8-12 inches) tall and wide when grown indoors, and far larger where it grows unrestricted (harvested far smaller as baby leaf for salads.). 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 mizuna 'red kingdom' slow or fast growing?

Mizuna 'Red Kingdom' is a fast grower. Expect a single growing season — it reaches full size in one year, then is done. Mizuna 'Red Kingdom' 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 mizuna 'red kingdom' 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 mizuna 'red kingdom' smaller?

Choose a compact or dwarf variety of mizuna 'red kingdom' 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 mizuna 'red kingdom' 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.