Mature size & growth rate

How big does Thunbergia erecta (Thunbergia erecta) get?

Also called Bush clock vine, King's mantle.

More about thunbergia erecta

About Thunbergia erecta

Thunbergia erecta · also called Bush clock vine, King's mantle · tropical

Thunbergia erecta, the bush clock vine or King's mantle, is an evergreen West African shrub grown for its near-continuous trumpet-shaped purple-blue flowers with golden throats. Unlike its climbing relatives it forms a tidy, self-supporting bush. It thrives in warm, frost-free gardens and makes a free-flowering container or conservatory plant in cooler climates.

Mature size: Typically 1-2 m tall and wide; reaches up to 2 m in ideal frost-free conditions, easily kept smaller in containers.

Indoor size vs how big it gets in the wild

Thunbergia erecta stays fairly low but widens over time — it spreads into a bigger clump by offsets, runners or rhizomes rather than shooting upward. Indoors and in a pot, expect typically 1-2 m tall and wide. In the ground with no restriction it is a completely different plant — reaches up to 2 m in ideal frost-free conditions, easily kept smaller in containers. — which is why the pot, the light and the pruning matter so much for the size you actually end up with.

Size here is about width, not height: the plant builds an ever-wider clump or sends out plantlets and runners while staying relatively short.

Growth rate and years to mature

Thunbergia erecta is a moderate grower. Realistically, expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Its feeding profile backs this up: feed every 2-4 weeks through spring and summer with a balanced or slightly phosphorus-rich liquid fertiliser to sustain bloom. ease off in autumn and stop in winter when growth slows.

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

How to keep thunbergia erecta smaller

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

Divide the clump every year or two — splitting thunbergia erecta is the main way to control its spread and refresh it.
Remove runners, plantlets or offsets as they appear if you want it to stay a single tight clump.
Keep it slightly pot-bound; a snug pot naturally limits how wide the clump can get.

The keep-it-smaller method, step by step

Lift the whole plant. Slide thunbergia erecta out of its pot in spring when the clump has filled it.
Split the clump. Tease or cut the rootball into two or more sections, each with healthy roots and growth.
Repot one division. Put a single division back in the original pot to reset it to a smaller size; pot or give away the rest.
Remove offsets as they form. Through the year, detach new runners or pups to stop it spreading again.

How to grow thunbergia erecta bigger or faster

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

Give it a wider pot and let the clump fill it — width is exactly how this plant gets bigger.
Good light plus regular feeding maximises offset and runner production.
Leave plantlets and offsets attached and feed through the growing season for the fastest spread.

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

When thunbergia erecta outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for thunbergia erecta:

The clump bulging over the pot rim or splitting the pot — the cue to divide, not to find a bigger room.
A dense centre that goes bare or tired while the edges keep spreading.
Runners or offsets escaping across the shelf or into neighbouring pots.

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

Thunbergia erecta size — frequently asked questions

How big does thunbergia erecta get?

Thunbergia erecta reaches typically 1-2 m tall and wide when grown indoors, and far larger where it grows unrestricted (reaches up to 2 m in ideal frost-free conditions, easily kept smaller in containers.). Size here is about width, not height: the plant builds an ever-wider clump or sends out plantlets and runners while staying relatively short.

Is thunbergia erecta slow or fast growing?

Thunbergia erecta is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Thunbergia erecta stays fairly low but widens over time — it spreads into a bigger clump by offsets, runners or rhizomes rather than shooting upward.

How long does thunbergia erecta take to reach full size?

Roughly three to six years to reach mature indoor size, gaining a steady amount each growing season. Light, pot size and feeding move that timeline more than anything else.

How do I keep thunbergia erecta smaller?

Divide the clump every year or two — splitting thunbergia erecta is the main way to control its spread and refresh it. Remove runners, plantlets or offsets as they appear if you want it to stay a single tight clump. Keep it slightly pot-bound; a snug pot naturally limits how wide the clump can get.

How can I make thunbergia erecta grow bigger or faster?

Give it a wider pot and let the clump fill it — width is exactly how this plant gets bigger. Good light plus regular feeding maximises offset and runner production. Leave plantlets and offsets attached and feed through the growing season for the fastest spread.