Mature size & growth rate

How big does Purple Basil (Ocimum basilicum 'Purpurascens') get?

Also called purple basil, dark opal basil.

More about purple basil

About Purple Basil

Ocimum basilicum 'Purpurascens' · also called purple basil, dark opal basil · herb

Purple basil is a striking deep-burgundy-leaved selection of sweet basil grown for both kitchen use and ornament, with a slightly spicier, clove-tinged flavour. A tender warm-season annual, it loves heat, sun and rich, moist soil, and rewards frequent pinching with bushy growth. Cold, wet conditions and the first frost will finish it off.

Mature size: 30-50 cm tall and 25-30 cm wide (12-20 in tall, 10-12 in wide)

Indoor size vs how big it gets in the wild

Purple Basil 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 30-50 cm tall and 25-30 cm wide (12-20 in tall, 10-12 in wide). A pot, your light levels and a little pruning are what set the final size in a home, far more than the plant's theoretical potential.

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

Purple Basil 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 modest feeder. in rich soil it may need nothing; otherwise feed every 3-4 weeks with a balanced or slightly nitrogen-leaning liquid feed at half strength to keep leaves coming. over-feeding dilutes the aromatic oils and the purple colour.

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

How to keep purple basil smaller

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

Choose a compact or dwarf variety of purple basil 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 purple basil bigger or faster

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

When purple basil outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for purple basil:

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 purple basil repotting guide. If you want more of this plant instead of a bigger one, the purple basil propagation guide turns prunings into new plants.

Purple Basil size — frequently asked questions

How big does purple basil get?

Purple Basil reaches 30-50 cm tall and 25-30 cm wide (12-20 in tall, 10-12 in wide) when grown indoors. 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 purple basil slow or fast growing?

Purple Basil is a fast grower. Expect a single growing season — it reaches full size in one year, then is done. Purple Basil 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 purple basil 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 purple basil smaller?

Choose a compact or dwarf variety of purple basil 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 purple basil 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.