Repotting guide

When & how to repot Water Forget-me-not (Myosotis scorpioides)

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

How to tell water forget-me-not needs repotting

Repotting on a calendar is less reliable than reading the plant. For water forget-me-not, watch for these signs:

Roots spiralling thickly out of the drainage holes or pushing the whole plant up out of the pot.
The pot is so packed that water runs straight through in seconds and barely wets the soil.
It has split a plastic pot, or the rootball is a solid mass with almost no soil left when you slide it out.
Growth and (for water forget-me-not) flowering have clearly stalled despite good light and feeding — but remember this plant likes being snug, so a little crowding alone is not a reason to repot.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot water forget-me-not

Only every 2–4 years, when genuinely crowded. Water Forget-me-not is one of the plants that genuinely prefers a snug pot — it grows and flowers better with its roots a little restricted, so resist the urge to repot it on schedule. Low, spreading, semi-aquatic perennial with creeping stems that root at nodes; soft, hairy, lance-shaped leaves; small, five-petalled, sky-blue flowers with yellow eye produced in curling cymes (typical scorpioid cyme of the Boraginaceae family).

What size pot to step water forget-me-not up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. Water Forget-me-not positively prefers a snug pot: it flowers and grows better when the roots are a little restricted. The single biggest repotting mistake here is over-potting — dropping water forget-me-not into a pot two or three sizes up. All that surplus soil holds water the small root system cannot use, stays cold and wet, and rots the roots within weeks. When in doubt, choose the smaller pot.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot water forget-me-not

Early spring, just as new growth restarts, is the ideal window for water forget-me-not. The plant is moving into its strongest growth phase and re-roots into fresh soil quickly. Avoid repotting in winter dormancy or, for flowering plants, while it is in bud or bloom — recovery is slowest then and you risk dropping the flowers.

Step-by-step: repotting water forget-me-not

Confirm it actually needs it. Slide water forget-me-not out and check the roots. Only continue if it is genuinely packed — this plant prefers a snug pot, so if there is still soil and room, put it straight back.
Pick a pot only one size up. Choose a pot just 2–3 cm wider with good drainage. Resist anything bigger; over-potting is the main killer here.
Ease it out gently. Water lightly the day before, then tip water forget-me-not out, supporting the base. Tease the outer roots free only enough to stop them circling.
Repot at the same depth. Add a layer of fresh moist to wet loam or clay; aquatic basket compost in containers, set the plant so the soil line sits exactly where it did before, and backfill around the sides, firming lightly.
Settle it in. Water once to settle the soil, then let it sit. Hold off on more water until the top of the soil dries — fresh soil around a small root system stays wet for a while.

Aftercare

Because the new soil holds more water than the old crammed rootball did, ease right back on watering — let the top of the soil dry before you water water forget-me-not again, or you will rot the roots in the very pot you just moved it to. Keep it out of harsh direct sun for a fortnight. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for water forget-me-not

Water Forget-me-not wants moist to wet loam or clay; aquatic basket compost in containers. Grows in a wide range of wet substrates from light loam to heavy clay, provided they remain permanently moist or saturated. Ordinary garden soil kept wet suits it perfectly. In containers, use aquatic basket compost or loam-based compost weighted with gravel to prevent the mix floating free. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting water forget-me-not — frequently asked questions

How often should you repot water forget-me-not?

Only every 2–4 years, when genuinely crowded for water forget-me-not. Only repot water forget-me-not every 2–4 years, and only when it is genuinely root-bound — it flowers and grows best slightly crowded. Step up just one pot size in spring using moist to wet loam or clay; aquatic basket compost in containers. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does water forget-me-not need?

When is the best time of year to repot water forget-me-not?

Does water forget-me-not like to be root-bound?

Yes — water forget-me-not genuinely flowers and grows best when slightly pot-bound, so do not rush to repot it. The mistake to avoid is over-potting into a much larger pot: the excess soil stays wet, the roots cannot use it, and the plant rots. Only repot every few years and only one snug size up.

Should you fertilise water forget-me-not after repotting?

Not immediately. Wait about 4 weeks after repotting water forget-me-not. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.