Mature size & growth rate

How big does Giant Arrowhead (Sagittaria montevidensis) get?

Also called Giant Arrowhead, Aztec Arrowhead, California Arrowhead, Giant Duck Potato.

More about giant arrowhead

About Giant Arrowhead

Sagittaria montevidensis · also called Giant Arrowhead, Aztec Arrowhead · flowering

Sagittaria montevidensis is a robust emergent aquatic perennial native to South America (Uruguay, Argentina, southern Brazil) and naturalised in parts of the southern United States and California. It produces very large, arrow-shaped leaves and impressive white three-petalled flowers with dark maroon basal spots on tall racemes throughout summer and into autumn. As the tallest and most dramatic Sagittaria species in cultivation, its most important care requirement is adequate depth — plant in water 10–15 cm (4–6 in) deep with full sun for maximum size and flower production. Sagittaria species are considered non-toxic to cats and dogs.

Mature size: Foliage 90–120 cm (36–48 in) tall; flower spikes to 150 cm (60 in); clump spread 45–60 cm (18–24 in) in a season.

Indoor size vs how big it gets in the wild

Giant Arrowhead 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 foliage 90–120 cm (36–48 in) tall. In the ground with no restriction it is a completely different plant — flower spikes to 150 cm (60 in); clump spread 45–60 cm (18–24 in) in a season. — 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

Giant Arrowhead 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: push 2–3 aquatic fertiliser tablets into the compost at the start of the growing season; reapply every 6–8 weeks through summer to maintain the high nutrient demand of this large, fast-growing species.

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

How to keep giant arrowhead smaller

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

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

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

When giant arrowhead outgrows the room (or the pot)

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

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

Giant Arrowhead size — frequently asked questions

How big does giant arrowhead get?

Giant Arrowhead reaches foliage 90–120 cm (36–48 in) tall when grown indoors, and far larger where it grows unrestricted (flower spikes to 150 cm (60 in); clump spread 45–60 cm (18–24 in) in a season.). 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 giant arrowhead slow or fast growing?

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

Divide the clump every year or two — splitting giant arrowhead 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 giant arrowhead 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.