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Greenhouse Capillary Matting: A Comprehensive Overview

Greenhouse capillary matting is a highly efficient method used for watering plants, ensuring they receive the right amount of moisture for optimal growth. This technique leverages capillary action to distribute water evenly, making it a favourite among both hobbyists and commercial growers. Here’s an in-depth look at greenhouse capillary matting, its benefits, applications, and how it works.

Capillary Matting Providing Water for a Selection of Plants and Seedlings in the Greenhouse

How Capillary Matting Works

Capillary matting utilizes a simple yet effective principle of capillary action, where water moves through small pores within a mat due to surface tension. This matting is placed on the benches in the greenhouse. Pots or trays of plants are set on top of the matting, which draws water from a reservoir and distributes it evenly. The mat remains moist, allowing plant roots to absorb water as needed, creating a self-regulating watering system.

Benefits of Capillary Matting

Consistent Moisture Levels: One of the primary advantages of capillary matting is its ability to maintain consistent moisture levels. Plants receive a steady supply of water, which is crucial for their health and growth.
Water Efficiency: This method significantly reduces water wastage. By providing water directly to the plant roots and minimizing evaporation, capillary matting is an eco-friendly choice.
Labour Saving: With capillary matting, the need for frequent manual watering is eliminated, saving time and energy. This is particularly beneficial in larger scale greenhouse operations.
Improved Plant Health: Consistent watering reduces stress on plants, leading to healthier growth. It also minimizes the risk of diseases caused by overwatering or underwatering.
Better Root Growth: Because moisture is entering the growing medium from the bottom plant roots go down to the water rather than remaining near the surface where they’re vulnerable to damage.
Protects Seeds and Seedlings: Overhead watering can disturb seeds and damage seedlings. Watering from below with capillary matting avoids this problem.
Cost-Effective: Once set up, capillary matting systems require minimal maintenance and are a cost-effective solution for long-term plant watering needs.

Applications of Capillary Matting

Capillary matting is useful in a range of horticultural settings:

Propagation of Seeds and Cuttings: Ensuring consistent moisture levels is vital during the propagation phase. Capillary matting provides an ideal, consistent environment for seed germination and rooting of cuttings.
Potted Plants: For growing on plants in pots, capillary matting offers an efficient way to keep the soil consistently moist without waterlogging.

Setting Up Capillary Matting

Setting up capillary matting in a greenhouse is straightforward and simple:

Prepare the Base

Most greenhouse benches have a slatted top which isn’t suitable for capillary matting. Wooden bench tops are not suitable either as the wood will be absorbing moisture and this will promote rotting.

Their are a number of ways to overcome this situation. Large plastic gravel trays are quite inexpensive and lightweight. These provide a waterproof surface to lay the matting on. Another solution is to lay thick polythene sheets, builders DPC material is excellent, on the surface under the matting. A very low cost option is to use old compost bags.

Lay the Matting

This is simply a matter of unfolding or unrolling the matting onto the base. If the matting overlaps the sides, it can easily be cut to size with household scissors or a box cutter.

Capillary Matting Sizes

Matting is available in a range of widths, typically 53cm, 60 / 61cm and 100cm. It is usually bought by the metre cut to length, from 1 metre to 50 metres.

Install a Water Source:

Place a water reservoir or tray at one end of the matting. Ideally the water surface in the reservoir will be fairly near the level of the benching. The matting will draw water vertically for around 10cm. The reservoir will need a cover to prevent the growth of algae.

The easiest and a very effective way to connect the reservoir to the bench matting is with a strip of matting around 10 to 15cm wide. One side is in the reservoir and the other is run under the matting for 20cm or so. The water will be drawn from the reservoir and taken by the main matting.

Once set up, ensure the matting can draw water efficiently from the reservoir.

An alternative is to set up a drip line adjusted to ensure the matting remains moist.

Capillary Matting Wick Laid Under Bench Matting

Home Made Free Water Reservoir

Whilst it is possible to buy reservoirs but they can easily be made for free as I have here – from used two litre ice cream boxes. The wick for conducting the water to the matting just lies on the base of the tub and then goes up and down the side to run under the bench matting.

Capillary Matting Water Reservoir – old 2 litre ice cream container

To prevent algae growth in the water, I use the original lid from the ice cream box, which has been cut back on one side to allow the wick room.

Capillary Matting Reservoir With Lid – Note Cut Down to Allow the Wick Room

Place Plants

Arrange the seed trays, pots or trays of plants on top of the matting. Ensure good contact between the pots and the matting for optimal water uptake.

Monitor and Maintain

Regularly check the water level in the reservoir and refill as necessary. Occasionally clean the matting to prevent blockages and ensure proper water distribution. Allowing the matting to dry and brushing is usually sufficient.

Cost & Lifespan

The price will vary according to the source and the amount bought. Generally the cost ranges between £4.00 and £8.00 per square metre.

Generally good quality capillary matting (available here) will last at least two years although I’ve had four years use in my greenhouses. Once the matting becomes flattened and thin it will not transmit water so well and the contact with the pots etc. will not be so effective, reducing water uptake.

Commercial nurseries often lay perforated plastic film over the matting which increases its lifespan. However, that only makes economic sense if bulk purchasing. With home growing the cost of the perforated protective film exceeds the savings from lengthening the life of the capillary matting.

Are capillary mats reusable?

Capillary mats are reusable for an extended period of time, and reasonably easy to clean. They can be sterilized with hot water with a spot of bleach added to maintain cleanliness.

Which Side is Up?

Many mats have two surfaces, a dark side and a white side. The darker surface on top is ideal for spring and autumn as it attracts and retains heat. The lighter colour on top helps reflect heat and light which aids fruit ripening. However, the light side looks dirtier than the dark with use.

Conclusion

Greenhouse capillary matting is a practical and efficient solution for maintaining consistent moisture levels in plant cultivation. Its benefits of water efficiency, labour savings, and improved plant health make it a valuable tool for both small-scale home gardeners and commercial greenhouse operators. By understanding how to set up and maintain a capillary matting system, growers can optimize their plant care routines and enjoy the rewards of healthy, thriving plants.

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