How to Improve Drainage in Raised Beds


Are you struggling with poor soil drainage in your raised bed?  If so, don’t fret – all is not lost.  There are steps you can take to solve the problem so that your raised bed will drain and your plants will grow.

So, how do you improve drainage in raised beds?  To improve drainage in a raised bed, loosen the soil, attract worms to your raised bed, and add the right soil amendments (such as compost, perlite, or vermiculite).  If you have not built your raised bed yet, be sure to choose a good site, use a good drainage system, and choose the right elevation for your raised bed.

Of course, it’s good to know why these measures work.  It’s also helpful to have a list of what types of soil amendments to use.  Let’s get into more detail about that now.

How to Improve Drainage in Raised Beds

There are some steps you can take before you build your raised bed to improve drainage – we’ll go over those first.  Then, we’ll talk about some ways you can improve drainage if your raised bed is already built.

How to Prepare a Raised Bed Site to Drain Better

Before you build your raised bed, there are a few things you can do to improve drainage and give your plants a better chance to grow well.

The first step is to choose a good site for your raised bed, so we’ll start there.

Choose a Good Site for Your Raised Bed

When choosing the ideal site for your raised bed, you will want to look at a few things:

  • the type of soil that will be under the raised bed
  • the amount of sunlight exposure in that area
  • the drainage pattern in the yard

Dig into the yard in a few places and see what type of soil you have.  If it is sandy, it may drain well without any additional work.  If it is heavy clay, it will hold moisture and will not drain as quickly.

sandy soil
Sandy soil will drain well – and carrots love to grow in it!

Choose a spot where the soil is sandy and loose, which will allow it to drain better.  Remember: for the water to drain out of the bottom of the raised bed, it has to go into the soil below!

Also, wait for a sunny day and see where the shady spots are in the yard.  You will want to avoid those shady spots.  Remember: trees that are bare in the winter will block out lots of sunlight when their leaves come out in the spring.  Think ahead before choosing a site for your raised bed – keep it away from trees that will provide too much shade!

daylight
Choose a spot without too much shade for your raised bed, and the soil will dry out faster.

Finally, take a look at your yard after a heavy rainstorm.  Are there any areas where water is pooling up?  If so, avoid those places for your raised bed!

If water is pooling up all over the yard after a storm, you might need to install a drainage system before you put in your raised bed.

Install a Drainage System for Your Raised Bed

A drainage system will help to remove water from the area where you put your raised bed.  There are two basic options: drainage pipes (above or below ground), or foundation material that drains well.

If you choose drainage pipes, don’t send the water towards your house, or towards a neighbor’s house.  Also, call before you dig to find out if there are any buried gas lines in your yard.

When choosing a material for the foundation below your raised bed, you will want something that drains well.  Remember that clay soil drains poorly, while sand drains well.  You can also use gravel as a medium to let water drain out of your raised bed faster.

clay soil
Clay soil drains poorly, so you may need to use sand or gravel under your raised bed.

Choose the Right Elevation for Your Raised Bed

A taller raised bed has more capacity to hold water from a rainstorm.  This means that your plants are less likely to suffer from over watering after summer rainstorms.  A taller raised bed is also more forgiving for beginner gardeners, who are prone to overwatering plants.

The only downside of a taller raised bed is that it will be difficult to access, especially if it is built for someone who is disabled.  One way around this problem is to build a raised platform around the raised bed (almost like steps) to make it easier to access the bed.

Use a Raised Bed Liner that Allows Drainage

Now that you have the right location and the right elevation for your raised bed, you may want to install a raised bed liner.  There are some good reasons for doing so – for more information, check out my article on raised bed liners, and what to use.

A good raised bed liner will allow water to drain away, without allowing soil to drain away.  You can use landscape fabric, canvas, or hardware cloth (metal mesh) to line your raised bed while also allowing drainage.

burlap canvas
Canvas is one possibility for a raised bed liner. It will allow water to drain through easily.

Don’t use a plastic liner that is non-permeable.  Otherwise, the water not drain, and your plants will suffer the consequences!

How to Improve Drainage in an Existing Raised Bed

If your raised bed is already built (or you now have the right location, height, and liner), it is time to take the next steps to improving drainage.  We’ll start off with

Add Soil Amendments

One of the most fun parts of gardening is playing with different soil amendments to make your plants grow better.  Some plants, like carrots, like smooth and sandy soil.  Others, like blueberries, prefer acidic soil.

You have some options when choosing soil amendments to improve drainage in your raised bed.  Here are a few options to consider.

First, you really should consider compost.  This is the granddaddy of all soil amendments.

compost bin
Compost improves drainage in heavy clay soils, and adds nutrients for your plants.

Compost is made from decomposed organic material, such as grass clippings, fallen leaves, dead plants, and kitchen scraps such as banana peels.  It is easy to make your own compost – for more information, check out my article on how to make your own compost.

You can even add manure to your compost pile!  Just make sure that it is completely decomposed before you add it to your garden.  If it is not decomposed, then the salts or nitrogen in the manure can harm young plants.

If you are considering growing carrots or other plants that prefer smooth soil, then sand might be just the thing for you.  Sand makes the soil smoother, and allows for much better drainage.

Just be careful to avoid sand that has salt in it – otherwise, you will kill your plants before they even get started!

Finally, you can consider perlite or vermiculite, which are two soil amendments that improve soil drainage.

  • Vermiculite holds more water, and so it is best for seedlings and plants that need more water.
  • Perlite holds less water and allows more aeration, so it can be used for plants with low water needs.

For more information about these two soil amendments, check out my article on perlite, vermiculite, and some alternatives.

Loosen & Aerate the Soil in Your Raised Bed

When soil is compacted, water cannot flow easily through the soil.  When you dig and move the soil around, you prevent compaction and aerate the soil at the same time.

When you aerate your soil, you create more space between particles, so that the water can move through faster.

shovel
Use a shovel or pitchfork to dig up your soil to loosen and aerate it.

Once your raised bed is built, using a rototiller to loosen the soil is out of the question (unless you use a very small and thin one!)  You will have to loosen your soil the old fashioned way – with muscle power!  Use a shovel or pitchfork to turn your soil over to loosen and aerate it.

­How to Get Worms for Your Raised Bed

As an alternative to digging, you can use worms to improve your soil structure and drainage!  Worms break down organic matter into soil, and they loosen and aerate the soil, allowing for better drainage.

You can buy worms online, at a bait shop, or at a garden center.  You can also transplant them from other areas of your yard, or from a neighbor’s yard.

earthworm
Earthworms help to loosen and aerate soil, while breaking down organic material to help plants to grow.

For more information, check out my article on how to get more worms in your garden.

Things You May Want to Avoid in Your Raised Bed

If you want to improve drainage a little more, then there are a couple of things to avoid in your raised bed.

First of all, avoid a liner that does not allow proper drainage (for instance, a prefabricated or makeshift plastic liner that does not allow water through).  This may save wood from rotting, but it will prevent proper drainage, which will eventually kill your plants!

Also, avoid mulch & other ground coverings that will retain moisture in the soil and prevent evaporation by sunlight & heat.

Conclusion

By now, you have some ideas about how you can improve the drainage in your raised beds.  You also know about some of the things to avoid so that you can prevent poor drainage in your raised beds.

I hope you found this article helpful – if so, please share it with someone who can use the information.

If you want more information, check out my article on how to make soil drain better, and my article on the signs of over watering your plants.

jonathon.david.madore

Hi, I'm Jonathon. I’m the gardening guy (not guru!) who is encouraging everyone to spend more time in the garden. I try to help solve common gardening problems so that you can get the best harvest every year!

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