Mature size & growth rate

How big does Aromatic Aster (Symphyotrichum oblongifolium) get?

Also called aromatic aster, shale aster, oblong-leaved aster.

More about aromatic aster

About Aromatic Aster

Symphyotrichum oblongifolium · also called aromatic aster, shale aster · flowering

Aromatic aster is a compact, exceptionally tough native perennial forming dense mounds of aromatic foliage topped by violet-blue daisies in late autumn. Among the last asters to bloom, it thrives in hot, dry, lean soils and full sun, resists mildew well, and rarely needs staking. Its balsam-scented leaves and very late flowers make it a pollinator standout.

Mature size: 60-90 cm (2-3 ft) tall and 90-120 cm (3-4 ft) wide, often wider than tall.

Watch for — Floppy growth in shade or rich soil: Too much shade or fertility opens up the normally tight mound. Grow in full sun and poor soil for its characteristic dense, self-supporting habit.

Indoor size vs how big it gets in the wild

Aromatic Aster 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 60-90 cm (2-3 ft) tall and 90-120 cm (3-4 ft) wide, often wider than tall.. 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

Aromatic Aster 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: best grown lean and unfed; fertiliser undermines its naturally compact, self-supporting habit and reduces drought toughness. do not fertilise in reasonable soil. container plants need at most one very light spring feeding.

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

How to keep aromatic aster smaller

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

Divide the clump every year or two — splitting aromatic aster 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 aromatic aster 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 aromatic aster bigger or faster

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

When aromatic aster outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for aromatic aster:

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

Aromatic Aster size — frequently asked questions

How big does aromatic aster get?

Aromatic Aster reaches 60-90 cm (2-3 ft) tall and 90-120 cm (3-4 ft) wide, often wider than tall. 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 aromatic aster slow or fast growing?

Aromatic Aster is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Aromatic Aster 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 aromatic aster 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 aromatic aster smaller?

Divide the clump every year or two — splitting aromatic aster 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 aromatic aster 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.