Mature size & growth rate

How big does Water Forget-me-not (Myosotis scorpioides) get?

Also called Water Forget-me-not, True Water Forget-me-not, Scorpion Grass.

More about water forget-me-not

About Water Forget-me-not

Myosotis scorpioides · also called Water Forget-me-not, True Water Forget-me-not · flowering

Water Forget-me-not is a delightful native European perennial producing a long succession of tiny, sky-blue flowers with yellow eyes from May to September along stream banks, pond margins, and in boggy ground — one of the longest-flowering native marginal aquatics. Its creeping stems root at the nodes, forming a mat of soft, hairy, lance-shaped leaves that spread across the water surface. A magnet for bees and hoverflies and an excellent wildlife pond plant. Not listed as toxic to cats or dogs by the ASPCA.

Mature size: 15–30 cm tall; spreading mat 30–60 cm or more across in good conditions

Watch for — Powdery mildew in late summer: The most common problem: white powdery coating on leaves appears in warm, humid, still conditions from August onwards. Cut plants back hard after the main flush of flowering in late summer; they typically regenerate a flush of clean new growth. Good air circulation reduces recurrence.

Indoor size vs how big it gets in the wild

Water Forget-me-not does not get tall — it gets long. Size here is about stem length and how you train or cut it, not how much floor it claims. Indoors and in a pot, expect 15–30 cm tall. In the ground with no restriction it is a completely different plant — spreading mat 30–60 cm or more across in good conditions — which is why the pot, the light and the pruning matter so much for the size you actually end up with.

Growth shows up as lengthening stems that trail down or climb up a support; the plant can be kept tiny or grown metres long from the exact same root system.

Growth rate and years to mature

Water Forget-me-not 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: little or no feeding required. in aquatic baskets, one slow-release fertiliser tablet in spring provides enough nutrition for the season. over-feeding promotes lush, soft growth susceptible to powdery mildew and reduces the long flowering period.

Want this turned into the right next pot at the right moment? The pot size calculator and the water forget-me-not repotting guide cover when and how much to size up — pot size is one of the biggest levers on how fast water forget-me-not grows.

How to keep water forget-me-not smaller

You are not stuck with the maximum size. For water forget-me-not specifically, these are the levers, in order of impact:

Trim the longest vines back to the length you want — water forget-me-not takes hard cutting well and bushes out from the cut.
Cut just above a leaf node; each trimmed stem usually branches into two, so pruning makes it fuller, not sparser.
The cuttings root easily in water or mix, so "keeping it smaller" doubles as free new plants.
A trim once or twice a season is usually enough to hold its length.

The keep-it-smaller method, step by step

Decide the length you want. Pick the point each vine of water forget-me-not should stop — you can be aggressive; it regrows readily.
Cut just above a node. Snip about 0.5 cm above a leaf node so the stem branches there instead of dying back.
Root the cuttings. Drop the trimmed pieces in water or mix — they root in 2-4 weeks and can fill the same pot for a bushier look.
Repeat as it runs. Re-trim whenever it overshoots; regular light pruning keeps it both smaller and fuller.

How to grow water forget-me-not bigger or faster

If you want it to fill the space sooner, push the conditions rather than hoping — for water forget-me-not the accelerators are:

Good light plus a moss pole or trellis triggers the longest, fastest, largest-leaved growth.
Give it something to climb — many vines grow far faster and bigger up a support than trailing.
Feed through spring and summer and keep it consistently watered while it is actively running.

Light is almost always the ceiling. The water forget-me-not light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When water forget-me-not outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for water forget-me-not:

Vines pooling on the floor or wrapping past where you want them — purely a trimming cue, not a repot one.
Bare, leggy stems with leaves only at the tips (usually a light problem, not a size one).
A tangled mass that has outrun its support and needs cutting back and re-training.

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

Water Forget-me-not size — frequently asked questions

How big does water forget-me-not get?

Water Forget-me-not reaches 15–30 cm tall when grown indoors, and far larger where it grows unrestricted (spreading mat 30–60 cm or more across in good conditions). Growth shows up as lengthening stems that trail down or climb up a support; the plant can be kept tiny or grown metres long from the exact same root system.

Is water forget-me-not slow or fast growing?

Water Forget-me-not is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Water Forget-me-not does not get tall — it gets long. Size here is about stem length and how you train or cut it, not how much floor it claims.

How long does water forget-me-not 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 water forget-me-not smaller?

Trim the longest vines back to the length you want — water forget-me-not takes hard cutting well and bushes out from the cut. Cut just above a leaf node; each trimmed stem usually branches into two, so pruning makes it fuller, not sparser. The cuttings root easily in water or mix, so "keeping it smaller" doubles as free new plants. A trim once or twice a season is usually enough to hold its length.

How can I make water forget-me-not grow bigger or faster?

Good light plus a moss pole or trellis triggers the longest, fastest, largest-leaved growth. Give it something to climb — many vines grow far faster and bigger up a support than trailing. Feed through spring and summer and keep it consistently watered while it is actively running.