Mature size & growth rate

How big does Agapanthus 'Navy Blue' (Agapanthus 'Navy Blue') get?

Also called Navy Blue agapanthus, dark blue lily-of-the-Nile.

More about agapanthus 'navy blue'

About Agapanthus 'Navy Blue'

Agapanthus 'Navy Blue' · also called Navy Blue agapanthus, dark blue lily-of-the-Nile · flowering

Agapanthus 'Navy Blue', often sold as 'Midnight Star', is a compact deciduous cultivar prized for its deep, almost violet-blue trumpet flowers in dense rounded umbels through mid to late summer. Its shorter stature suits containers and small borders. Like other hardy agapanthus it flowers most freely in full sun and sharp drainage with congested roots.

Mature size: 60-80 cm tall in flower and around 45 cm wide, more restrained than tall border types and ideal for pots.

Indoor size vs how big it gets in the wild

Agapanthus 'Navy Blue' 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 60-80 cm tall in flower and around 45 cm wide, more restrained than tall border types and ideal for pots.. 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.

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

Agapanthus 'Navy Blue' 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: from spring to flowering apply a high-potash liquid feed such as tomato food every 2-3 weeks to deepen colour and lift bloom count; cease after flowering and avoid nitrogen-heavy feeds that push leaf growth.

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

How to keep agapanthus 'navy blue' smaller

You are not stuck with the maximum size. For agapanthus 'navy blue' specifically, these are the levers, in order of impact:

Divide the clump every year or two — splitting agapanthus 'navy blue' 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 agapanthus 'navy blue' 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 agapanthus 'navy blue' bigger or faster

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

When agapanthus 'navy blue' outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for agapanthus 'navy blue':

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 agapanthus 'navy blue' repotting guide. If you want more of this plant instead of a bigger one, the agapanthus 'navy blue' propagation guide turns prunings into new plants.

Agapanthus 'Navy Blue' size — frequently asked questions

How big does agapanthus 'navy blue' get?

Agapanthus 'Navy Blue' reaches 60-80 cm tall in flower and around 45 cm wide, more restrained than tall border types and ideal for pots. when grown indoors. 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 agapanthus 'navy blue' slow or fast growing?

Agapanthus 'Navy Blue' is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Agapanthus 'Navy Blue' 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 agapanthus 'navy blue' 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 agapanthus 'navy blue' smaller?

Divide the clump every year or two — splitting agapanthus 'navy blue' 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 agapanthus 'navy blue' 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.