Repotting guide

When & how to repot Moonflower (Ipomoea alba)

Also called Moonflower, Moon vine, Tropical white morning glory.

More about moonflower

About Moonflower

Ipomoea alba · also called Moonflower, Moon vine · flowering

Moonflower is a fast-growing night-blooming vine producing large, intensely fragrant white flowers up to 6 inches across that open at dusk. Grow in full sun on a sturdy support. Treat as an annual in temperate climates; seeds require nicking before sowing. Keep away from pets — seeds contain hallucinogenic indole alkaloids.

Mature size: 3–6 m (10–20 ft) in a single season as an annual; up to 20 m (70 ft) as a perennial in tropical climates

Watch for — Root rot: Overwatering or heavy, poorly drained soil causes wilting and stem collapse at the base. Ensure sharp drainage and allow the soil surface to dry slightly between waterings.

How to tell moonflower needs repotting

Repotting on a calendar is less reliable than reading the plant. For moonflower, 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 moonflower) 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 moonflower

Only every 2–4 years, when genuinely crowded. Moonflower 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. Vigorous twining vine.

What size pot to step moonflower up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. Moonflower 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 moonflower 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 moonflower

Early spring, just as new growth restarts, is the ideal window for moonflower. 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 moonflower

Confirm it actually needs it. Slide moonflower 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 moonflower 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 well-draining loamy or sandy soil, 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 moonflower 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 moonflower

Moonflower wants well-draining loamy or sandy soil. Prefers moderately fertile, well-drained soil. Overly rich soil promotes leafy growth at the expense of flowers. Heavy clay must be amended with grit or coarse perlite. pH 6.0–7.5. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting moonflower — frequently asked questions

How often should you repot moonflower?

Only every 2–4 years, when genuinely crowded for moonflower. Only repot moonflower 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 well-draining loamy or sandy soil. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does moonflower need?

When is the best time of year to repot moonflower?

Does moonflower like to be root-bound?

Yes — moonflower 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 moonflower after repotting?

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