Can plant roots puncture a pond liner? The real risks and solutions

The water level drops by a few centimeters per week, with no visible leak at the filter or waterfall, and a worrying thought takes hold: what if the plant roots had pierced the liner? The concern is not unreasonable, but it is often misplaced. The fine roots of aquatic plants do not pierce an intact liner; the risk mainly comes from a few species with pointed, spreading rhizomes, and from trees or bamboo planted too close to the pond.

How a root could pierce a membrane

A growing root exerts pressure at its tip. Against a smooth, continuous surface such as a liner, a thin, flexible root simply follows it: this is why, when dismantling an old pond, you often find a mat of roots pressed against the membrane without a single hole. The problem arises when two conditions combine: a hard, pointed organ and a weak spot in the membrane, such as a fold, an area thinned by aging, or a stone pressing against it from underneath.

Species to monitor

This ranking reflects the field experience of pond builders, who avoid planting species with penetrating rhizomes directly against the liner. It is not a percentage risk assessment, but a hierarchy of caution.

EPDM or PVC: not all materials are equal

The membrane's thickness and elasticity matter. A good-thickness EPDM liner, flexible and elastic, deforms under a sharp point rather than giving way, and it ages slowly. A thin PVC liner, especially after several years of UV exposure on the banks, becomes more rigid and fragile. A sharp rhizome lodged in a fold of the liner is the worst-case scenario: the membrane is stretched, doubled over, and unable to deform. Taking care during installation and limiting folds therefore also reduces this risk.

Preventive measures, from construction to maintenance

During construction. Lay geotextile fabric beneath the entire liner: it protects against stones and roots coming from the soil. In planting areas where you plan to add substrate directly on the ground, add a second layer of geotextile over the membrane. Also keep trees and bamboo at a distance; for an already established running bamboo, a vertical rhizome barrier between it and the pond is essential.

When choosing plants. Ban common reed from lined ponds and grow vigorous species, such as cattails, in containers. A basket or tub confines the rhizomes, makes division easier, and prevents them from exploring the folds of the membrane.

During maintenance. Every two or three years, lift the baskets and check that no rhizome has escaped toward the liner. Cut back any that protrude. In areas planted directly in the ground, occasionally clear around the base of the most vigorous clumps to control their spread.

The water level is dropping: are the roots to blame?

Before blaming the plants, eliminate the more common causes. First, evaporation, which can amount to several millimetres per day in midsummer depending on sunlight and wind, as agronomic references on evapotranspiration remind us. Marginal plants themselves transpire a great deal of water. Then there are "hydraulic" leaks: fittings, waterfalls, or a collapsed liner edge allowing water to pass through the soil by capillary action. A simple test is to switch off the pump and mark the water level: if it stabilizes at a certain height, the leak is above that line.

Repairing a puncture caused by a rhizome

If you do find a hole, first remove the responsible plant or cut the rhizome, then clean and dry the area. On EPDM, use a primer and a compatible patch or sealant; on PVC, use a specific repair kit with suitable adhesive. Take the opportunity to slide a piece of geotextile under the repaired area if the soil underneath contains stones.

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Frequently asked questions

— Can water lily roots puncture an EPDM liner?

This is very unlikely. Water lilies have slow-growing rhizomes and fibrous roots that run along the liner without puncturing it, especially when grown in a basket.

— Which plants should not be put in a liner pond?

Above all, common reed, whose pointed rhizomes are known to cause punctures. Running bamboo should be kept at a distance, and cattail should be grown in a container.

— Is geotextile under the liner enough?

It protects against stones and roots from the soil. In areas planted directly in the ground, a second layer placed over the liner adds protection on the inside.

— My pond is losing water - is it necessarily a root?

No. Evaporation, transpiration from marginal plants, a connection, or a sagging liner edge are much more common causes.

In summary

• The fibrous roots of common aquatic plants do not puncture an intact liner.
• Pointed rhizomes (reed, bamboo, cattail) and nearby trees are the real risks.
• Folds and thin or aged membranes are the weak points.
• Geotextile under the liner, and on top in planted areas; vigorous species in containers.
• A drop in water level is much more often caused by evaporation or a connection than by a root.

Last updated: September 29, 2026.