What is drain matting and why is it used in raised garden bed liners?

Drain matting is a porous liner material placed at the base of a raised garden bed or container. It lets water flow out freely while stopping the growing medium from washing out with it. Think of it as a filter: water passes through, the potting mix stays put.

Why does it matter in a raised bed?

Without some kind of drainage layer, two things can go wrong. The potting mix can block drainage holes and cause water to pool at the bottom, leading to root rot. Or the mix can wash out through any gaps, wasting it and making a mess.

A good drainage solution solves both problems at once.

How Corrogarden raised beds handle this:

Our raised beds include a recycled plastic tub liner at the base. This tub has a pattern of small breather holes built into it, which serve as both the drainage layer and the liner in one. Water drains away freely, air reaches the roots from below (which is what the breather holes are specifically designed for), and the premium potting mix stays where it belongs.

This is why you do not need to add separate drainage materials such as gravel, scoria or drain matting to the bottom of a Corrogarden bed. The tub does that job, and adding a heavy layer of gravel on top of it can actually restrict root depth for no benefit.

What about other raised beds or containers?

If you are using a container without a built-in drainage layer, a piece of weed matting or geotextile fabric across the base works well. Avoid solid plastic sheeting, which traps water. And always make sure there are actual drainage holes in the container itself, because matting alone cannot fix a sealed base.

For more on setting up your Corrogarden bed correctly, see our filling guide. For why drainage matters, see our guide to drainage in raised beds.

What should I plant right now? Our free planting calendar shows what suits your postcode this month. Ready to grow? Browse our raised garden beds or build your own with the garden bed builder.

Image: CC0, via Wikimedia Commons.