Greenhouse Capillary Matting: Setting Up a Watering Bench

Illustration of staging and potted crops inside a greenhouse

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Capillary matting can supply water to suitable greenhouse pots through their drainage holes. It works only when the mat, compost and water supply maintain good contact. Set up and test the bench before relying on it, because different pots and composts can take up very different amounts of water.

Table of Contents

Choose plants that suit shared moisture

Group plants with similar watering needs. Many small pots can benefit from a steady supply, but plants needing dry intervals may become too wet. Keep those on a separate surface and water them individually.

A mat is not a sensor that gives every plant exactly what it needs. Check compost moisture and drainage, including pots at the edges and far end of the bench.

Prepare a level, waterproof surface

Use a tray or bench liner designed to contain moisture and protect the staging. Check the bench’s load rating for pots, wet compost and any reservoir together. Position water away from electrical connections and keep the path clear.

Lay suitable capillary matting flat and pre-wet it according to its instructions. Some systems use a wick down into a separate reservoir; others have a purpose-made tray and reservoir. Follow the permitted lift height and layout for the product rather than assuming a long strip will draw from any depth.

Make reliable contact with the pots

Water dry compost appropriately before placing pots on the wet mat.
Check that moist compost at drainage holes can make contact with the mat or the system’s specified wick.
Remove unnecessary gaps in the arrangement; deep recessed pot bases or a layer of crocks can interrupt contact.
Check each pot after several hours and over the following days to see whether water reaches its compost.
Adjust the grouping or change the system if some pots remain dry or saturated.

Plastic pots are commonly used. Terracotta can also work, but the RHS advises watering clay pots thoroughly first. Peat-free mixes differ in structure and wicking behaviour, so test the actual compost rather than assuming the label alone establishes suitability.

Size and monitor the reservoir

Keep the wick in contact with the water as the level falls, within the product’s permitted lift. Secure it so it cannot slip. Protect an open reservoir appropriately where children or animals could access it.

Measure how quickly the level drops under typical greenhouse conditions. Hot weather and larger plants can increase demand sharply, so a test in cool weather does not establish how many days the system will last during a heatwave. Arrange someone to check it during longer absences.

Troubleshoot moisture directly

If a pot is dry, check the reservoir, wick position, mat wetness and pot-base contact. Water the plant appropriately while correcting the fault. Leaf symptoms or pests alone do not prove that the mat has failed.

If compost stays saturated, remove the pot from the mat and allow it to drain. Reassess whether that plant suits the system; moving it to another wet part of the same mat may not solve the problem.

Keep the bench clean

Remove dead leaves and spilled compost, inspect for algae and follow the mat maker’s cleaning or replacement instructions. Shared wet surfaces can carry contamination, so keep diseased plants separate. Check fertiliser buildup and follow crop-specific feeding guidance rather than adding feed to a reservoir automatically.

Useful products for this job

The links below open Amazon UK product searches. Check the exact item, seller, current price and compatibility before buying.

Capillary matting: The primary material required to create the wicking bridge between the reservoir and the plants. Ensure the material is specifically designed for capillary action (wicking) rather than just being a moisture-retaining liner. Search Amazon for Capillary matting.
Plastic nursery pots: Compatible pot bases help moist compost contact the capillary mat. Check the drainage-hole position and base recess, then test uptake with the actual compost; plastic alone does not guarantee compatibility. Search Amazon for Plastic nursery pots.

Related garden guides

Sources and further guidance

Guidance researched in September 2026. The feature image is an AI-generated illustration. Product guidance is based on published information, not hands-on testing.