Repotting and Dividing Water Lilies and Aquatic Plants: When, How, and Mistakes to Avoid

A pond planted for several years eventually always starts to look like a jungle: water lilies with leaves standing out of the water, irises overflowing from their baskets, roots breaking through the sides and clinging everywhere. Dividing and repotting aquatic plants is like pruning a fruit tree: a routine operation that restores their vigor and flowering. Here is how to do it successfully, plant by plant.

Signs that it is time to repot

• The water lily leaves stand upright out of the water instead of spreading flat.
• Flowering decreases year after year despite good sunlight.
• The roots grow out of the basket and anchor themselves in the bottom or on the liner.
• The basket becomes misshapen or splits under the pressure of the rhizome.
• The center of the clump becomes sparse in marginal plants (irises, rushes, sedges), with vigor remaining only around the edges.

The right time

Spring is ideal: between April and early June, when the water warms up and the first shoots appear. The plant enters full growth and heals quickly. You can still intervene until July on marginal plants, but avoid late summer and autumn: the divisions would not have time to establish before winter.

Dividing a water lily, step by step

1. Take the basket out of the pond. It is heavy: an established water lily in a basket saturated with water can quickly weigh 15 to 25 kg. Slide a board or tarp underneath.
2. Cut open the basket if the roots have invaded it, rather than forcing them: you would damage the rhizome.
3. Rinse the rhizome with a hose to see its structure. It is a kind of thick, creeping stem with buds and “eyes.”
4. Cut 10 to 15 cm sections with a clean, sharp knife, each bearing a terminal bud and a few young leaves. Remove old woody, hollow, or soft sections.
5. Clean the roots and shorten the longest ones.
6. Replant each section horizontally, with the bud slightly raised and level with the soil, against the edge of the basket so it grows toward the center.
7. Cover with 2 to 3 cm of washed gravel, without covering the bud, to prevent fish from digging.
8. Lower gradually: first place the basket at a shallow depth on bricks, then lower it to its final depth over the following weeks as the leaves lengthen.

Don't keep every piece: one vigorous section per basket produces a better-looking plant than three pieces competing for space. Give the others away or plant them in another pond.

Dividing marginal plants

Irises, rushes, sedges, pontederia, and arrowheads are divided like garden perennials. Remove the root ball, cut it into quarters with a spade or knife, keep the most vigorous outer sections, and discard the exhausted center. Cut the leaves back by half to limit evaporation while they re-establish, then replant.

The right substrate and the right basket

Garden soil is too light and too rich: it floats, clouds the water, and releases nutrients that feed algae. Aquatic soil is designed to stay in place and nourish the plant at root level.

Read also

How do you plant water lilies?

READ THE ARTICLE

Frequently asked questions

— Can a water lily be transplanted in midsummer?

It is possible but delicate: the plant is in full bloom and recovers less well. If it is essential, do it early in the morning, keep the rhizome moist, and cut off the large leaves.

— How often should a water lily be repotted?

Generally every three to four years, more often for very vigorous varieties. The signs are unmistakable: upright leaves, reduced flowering, roots growing out of the basket.

— Can plant roots damage the liner?

Some plants with pointed rhizomes, such as reeds and water bamboo, can puncture a thin liner. This is why it is best to keep them in baskets and repot them before their roots grow out.

— Should fertilizer be added when repotting?

Yes, in the form of tablets or slow-release granules placed at the bottom of the basket, never in the water. New aquatic soil is often sufficient for the first season, then topped up each spring.

In summary

• Every 3 to 4 years, in spring.
• One vigorous section with a bud per basket, for water lilies.
• Perforated basket, burlap, heavy aquatic soil, gravel.
• Gradually lower it to the final depth.

Last updated: September 28, 2026.