Black mulching fabric: what it is for and how to mulch vegetable beds

Mulching with black fabric is one of the easiest ways to stop weeding and keep moisture in the soil. Here we explain what black mulching fabric is for, how it works and how to lay it and pin it down properly.

What black mulching fabric is for

Mulching (black) fabric is a non-woven material for covering the soil. It is spread over a bed, and plants are set into cuts in it. What it does:

• Weed control. The black fabric blocks light, so weeds cannot grow underneath.
• Moisture retention. The fabric reduces evaporation, the soil stays moist for longer and you need to water less often.
• Faster soil warming in spring. Black absorbs heat, so the soil under the fabric warms up earlier.
• Frost protection for roots. A layer of fabric protects plant roots from frost.
• Clean berries and fruit. Strawberries and vegetables rest on the fabric rather than on the soil, which means less rot and dirt.

Uses: strawberries, vegetables, ornamental plantings, and the spaces and paths between beds.

Black or white fabric

White fabric (garden fleece) lets light through: it is laid over plants to protect them from frost, sun and pests. Black fabric blocks light, so it is laid on the soil, under the plants. They are different tools for different jobs and are often used together.

Does black mulching fabric let water through

Yes. Mulching fabric is non-woven, so water passes through it into the soil. So why does it sometimes seem that the fabric does not let water through?

• Dry fabric. At first, water may sit on the surface in droplets until the fibres get wet.
• A heavy flow. If you pour a lot of water onto one spot, it runs off across the surface faster than it can soak in.
• Compacted soil under the fabric. Water passes through the fabric but is not absorbed by the compacted ground and forms puddles.
• Dirt. Over time, dust and clay clog the surface of the fabric.

The best solution is drip irrigation under the fabric: the tube is laid before the fabric goes down and held in place with 19 cm drip tube holders, which stop it from moving. Water goes straight to the roots and does not evaporate.

Which weight to choose

For mulching, black fabric of around 50 g/m² is used: it is strong enough to last under plants and still lets water and air through. Gartec black mulching fabric has a weight of 50 g/m² and a UV stabiliser additive. A roll is 3.2 × 100 m, i.e. 320 m².

When to lay mulching fabric

Black fabric is most often laid in spring, before planting out seedlings: the soil underneath warms up faster and the plants get off to an earlier start. For strawberries, the fabric can also be laid at the end of summer, before planting runners in autumn. The main thing is not to lay it on cold, waterlogged soil: let the ground dry out and warm up first.

How much fabric you need

A Gartec roll is 3.2 m wide and 100 m long. Work out how many running metres of fabric your plot will take, allowing for overlaps and extra for burying the edges. For example, a 10 × 3 m strawberry patch is covered by a single 3.2 m wide strip: you need about 10.5 m of fabric with extra for the edges. One roll is enough for about nine such patches.

How to lay black mulching fabric, step by step

1. Prepare the bed. Dig over the soil, pick out the roots of perennial weeds, add fertiliser and level the surface with a rake. Feeding will be harder under the fabric, so prepare the soil in advance.
2. Water. Lay the fabric on moist soil.
3. Lay the drip tube. Run the tubes along the rows and fix them with holders.
4. Spread the fabric. Unroll it along the bed. Cover large areas with several strips overlapped, usually by 10–20 cm, so weeds cannot push through the seam.
5. Pin it down with stakes. Fix the fabric with landscape fabric stakes along the edges and the joints. The edges can also be buried in soil so the wind cannot get underneath.
6. Make cuts. Mark the planting positions and make cross-shaped cuts with a knife. Fold the flaps inwards.
7. Plant. Set the seedlings into the cuts and water at the root.

How to pin down mulching fabric

Gartec stakes are 19 cm long, 30 mm wide and made of polypropylene. They are non-toxic, resistant to UV, moisture and mould, and have an unlimited shelf life. The stakes also work for geotextile, plastic film and other covering materials.

Stakes are usually placed around the edges and along the joints every 0.5 to 1 m, closer together on exposed, windy sites. The number depends on the length of the edges and joints: measure them in metres and divide by the chosen spacing.

Mulching fabric for strawberries

Strawberries are the main crop that black fabric is laid under. The berries rest on dry, clean fabric instead of wet soil, so they rot less and do not get dirty after rain. Runners do not root wherever they like, and the bed needs no weeding.

A few tips specifically for strawberries:

• shape the beds in advance and add organic fertiliser before laying the fabric, as feeding under the fabric is awkward later;
• keep the cuts small, just big enough for the crown, so that the heart of the plant stays above the fabric;
• use drip irrigation, which is especially convenient for strawberries;
• plan the spacing between plants and rows before making the cuts, as the holes cannot be moved later.

Under perennial strawberry plantings, the fabric is left for several seasons, until you renew the patch.

Mulching between rows and on paths

The spaces between beds can also be covered with black mulching fabric pinned down with stakes: no weeds, and the paths stay dry. To keep soil from the beds spilling onto the fabric, plastic edging is set along the edges of the beds.

Mulching fabric under ornamental plantings

Under shrubs, conifers and in mixed borders, black fabric also does away with weeding. Here it is often covered with decorative mulch such as bark, wood chips or pebbles. The fabric stops weeds from growing up from below, while the mulch shields it from direct sun and makes the planting look neat. The edges of such a bed are easily finished with flexible edging so the mulch does not spill onto the lawn.

Common mistakes

• laying it on unprepared soil with weed roots: perennial weeds find their way to the light through the cuts;
• not pinning the fabric down: the wind blows it away and tears it;
• seams without an overlap: weeds grow through the gaps;
• large cuts: weeds grow next to the plants;
• watering from above with a strong jet: the water runs off the fabric.

Care and storage

At the end of the season, the fabric is lifted, cleaned of soil, dried and rolled up for storage, so it can be used again. On perennial plantings such as strawberries, the fabric is left for several seasons.

Prices and ordering

Mulching fabric, stakes and holders are in the mulching and irrigation section. Prices are listed in the catalogue and drop from 10 units. Farms and shops get wholesale terms in the customer account.