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Planter Box and Raised Garden Bed Drainage: A Simple Guide

There are various ways that you can ensure that your raised garden bed or planter box has excellent drainage. We cover the easiest and most effective methods.

Raised garden beds and planter boxes have soared in popularity over recent years because they allow people everywhere to grow their own fresh produce and flowers even if they don’t have a suitable garden space.

Like all container-grown plants, good drainage is vitally important for your raised garden bed or planter box. You need to ensure that excess water can easily drain away so that the soil in your garden bed doesn’t become saturated and waterlogged.

Why good drainage is important

The roots of healthy growing plants need water, air, and nutrients easily accessible in the soil they’re growing in.

If the soil becomes waterlogged and excess water cannot drain away easily, the water will fill the tiny air spaces in the soil. This means that the roots don’t have access to the oxygen that they need and will essentially, suffocate.

Additionally, waterlogged soil can cause the roots to rot which means the end of your healthy crop of plants.

Growing in raised beds improves soil drainage

raised garden bed | Plant care

The good news is that if you’re growing in raised garden beds or planter boxes, you already have the advantage when it comes to drainage.

This is because you have complete control over the type of soil that you fill your raised beds with. Therefore, instead of having to deal with heavy clay soils that are not free-draining or very light sandy soils that don’t hold much moisture, you can select just the right type of free-draining and moisture-retaining soil.

So, choosing the perfect soil for your raised garden bed or planter box is the first step to ensuring that your garden bed has good drainage.

How you can improve the drainage in your raised garden bed

raised garden bed 2 | Plant care

There are various ways that you can ensure that your raised garden bed or planter box has excellent drainage. Here are just a few to consider.

Select a good quality sandy loam

When filling your raised garden beds, make sure that you select a good quality sandy loam that is well-draining. The soil should be open and friable and contain lots of organic matter.

It’s also a good idea to fork over the soil in between crops to aerate it and improve drainage.

Add soil amendments to an existing raised garden bed

If you already have an existing raised garden bed and you’re finding that the soil seems a little compacted and is not draining well, you can easily add some soil amendments to improve the structure and drainage of the soil.

By far the best amendment you can add is compost. Compost is full of nutritional goodness for your plants and if you fork it in well, will reward you with an amazing crop of plants that are not suffering from waterlogging.

Other products you can use include builder’s sand, composted wood chips, or even perlite.

Add some worms to your raised garden bed

Worms are excellent in breaking up the soil and creating more air spaces to assist in drainage. As they tunnel their way through the soil, they create spaces for oxygen.

Plus, their castings are excellent food for your growing plants.

Don’t line the base of your raised garden bed with rocks or gravel

It’s a common myth that putting rocks or gravel into the base of a raised garden bed or planter box assists the drainage. This is simply not the case.

Instead, it increases the water saturation of the soil as the water pools in the base of the garden bed.

A better choice for lining the base of your raised garden bed is to use high-quality landscape fabric, a thick layer of cardboard, or even hessian or canvas.

All these materials should allow the water to drain away into the soil below without the loss of soil from your garden bed.

Choose the right location for your raised garden bed

rain in garden | Plant care

Make sure that you position your raised garden bed or planter box in a spot where water is not likely to pool if you experience a lot of rain where you live.

For this, you want to have a look at your outdoor space after a bout of heavy rain and take note of where the water tends to gather. If you do have a problem with pooling water, consider creating a raised garden bed that is quite tall.

The higher your garden bed is, the more soil you’ll have and this helps to allow the water to drain down further and away from the roots of your plants.

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Annette Hird

Annette Hird is a gardening expert with many years of experience in a range of gardening related positions. She has an Associate Diploma of Applied Science in Horticulture and has worked in a variety of production nurseries, primarily as a propagator. She has also been responsible for a large homestead garden that included lawn care, fruit trees, roses and many other ornamental plants. More recently, Annette has concentrated on improving the garden landscape of the homes that she has lived in and focused a lot of energy on growing edible plants as well. She now enjoys sharing her experience and knowledge with others by writing articles about all facets of gardening and growing plants.

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