Mature size & growth rate

How big does Scarlet Giant Hyssop (Agastache coccinea) get?

Also called Scarlet Giant Hyssop, Red Giant Hyssop.

More about scarlet giant hyssop

About Scarlet Giant Hyssop

Agastache coccinea · also called Scarlet Giant Hyssop, Red Giant Hyssop · flowering

Scarlet Giant Hyssop is a striking North American perennial bearing vivid scarlet to orange tubular flower spikes from midsummer into autumn, irresistible to hummingbirds and long-tongued pollinators. More heat- and drought-tolerant than many Agastache species, it suits sunny, well-drained borders and xeriscape gardens. Often treated as a short-lived perennial or annual in cooler climates.

Mature size: 60–100 cm tall, 40–60 cm wide

Indoor size vs how big it gets in the wild

Scarlet Giant Hyssop 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 60–100 cm tall, 40–60 cm 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.

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

Scarlet Giant Hyssop 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: apply a low-nitrogen, balanced fertiliser once in spring. excess nitrogen promotes leafy growth at the expense of flowers. in poor, sandy soils, a top-dressing of compost in spring is sufficient. no supplemental feeding needed in average garden soils.

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

How to keep scarlet giant hyssop smaller

You are not stuck with the maximum size. For scarlet giant hyssop specifically, these are the levers, in order of impact:

Divide the clump every year or two — splitting scarlet giant hyssop 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 scarlet giant hyssop 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 scarlet giant hyssop bigger or faster

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

When scarlet giant hyssop outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for scarlet giant hyssop:

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

Scarlet Giant Hyssop size — frequently asked questions

How big does scarlet giant hyssop get?

Scarlet Giant Hyssop reaches 60–100 cm tall, 40–60 cm wide 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 scarlet giant hyssop slow or fast growing?

Scarlet Giant Hyssop is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Scarlet Giant Hyssop 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 scarlet giant hyssop 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 scarlet giant hyssop smaller?

Divide the clump every year or two — splitting scarlet giant hyssop 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 scarlet giant hyssop 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.