How To Improve Drainage In Raised Garden Beds

Raised garden beds are a ​terrific upgrade to traditional gardening, especially if you do not have a vast area available or if you are confined to urban settings. But one issue which gardeners face often is trouble with proper drainage. It might seem a trivial matter but it is the opposite in fact. Hence, in this article ​we have provided some tips and tricks ​on how to improve drainage in raised garden beds, ​which could enhance your gardening experience overall.

Raised garden bed

​Improper drainage not only includes excess water retention, but also water seeping away too quickly​. Rapid drainage of water deprives the plants ​a chance to absorb the adequate moisture they need. In either case, improper drainage can be due to several factors. The soil quality or texture, inadequate aeration, construction of the bed, awkward elevations - all these can lead to poor drainage. Therefore, try to figure out the cause of this problem first.  

Regardless of the cause, below we have shared some simple ideas that ​could have a significant impact on the drainage in raised garden beds. Do give them a try!

1. ​suitable site

This ​tip is for those you haven't built a bed yet. Choose a good site for your garden bed as the type of soil in that ​area plays a crucial role in drainage. This is because, the water that is flow out of the bed will be traveling into the soil below eventually. Figure out what type of soil you have in your yard and ensure you have enough sunshine available. Sandy soils tend to loose water with much extra work, while heavy clay does not drain so quickly. You would want something in between - not TOO ​MUCH of either type. Also, if you have ​places in your yard where small water pools are formed after heavy rainfall - avoid those spots. If all of your yard tends to pool up, then invest on a good drainage system first before raising a bed.

Proper site

​2. ​​Drainage holes in raised beds

​There are mainly types of raised garden beds: one which doesn't have a base and in is opened to the ground and the other which has a base (like a water trough) and is not connected to the ground. ​The first type (without ​a base) uses the height ​primarily for ​drainage. That is, the water from the soil of the planter ultimately drains down​ towards the topsoil on the ground. For such beds, drainage holes might not be mandatory, given there is ample space for the roots to spread along with some extra depth beneath. However, if for some reason you feel additional drainage is necessary, you can drill some holes on the sides. ​How many? That depends on the area of the bed and how much effluence you need.

Drainage holes

​For the second type of bed (with a base), you must have holes on the bottom of the structure, no matter how deep it is. Otherwise, it'll just be a giant pot. If the beds already have hole on the, great. If not, do drill some with uniform gaps. Be wary that these holes might get clogged up over time. To avoid this, use a degrading shade cloth or bed liner to cover the outlets. This will inhibit blockage while still allowing water to seep through.

​3. ​Rocks & gravels

Drainage rocks placed at the bottom of a bed work very well. Before adding soil, spread the rocks inside the designated frame in a uniform layer (preferably 2 or 3 inches thick) using hands or rakes.

Crushed granite or something similar posses impressive drainage properties as well as being economic and easy to apply.

Other stones like pebbles or bluestone could also be used, but the top soil tends to leach into these rocks and reduce their efficacy.

Another option includes crushed rock or pea gravel, specifically for beds that are over 18 inches in height.

Rock bottom

Sand can also be used to improve drainage in raised garden beds. But not just any sand; river or washed sand performs best as they don't contain excess salt. Salt is notorious for retaining moisture and tends to disrupt the growth of vegetative crops.

​4. ​Soil amendments

Soil amendments do exactly what the name suggests. They alter the texture of the soil. The precise outcome depends on the type of amendment in use. Tilth, for instance, is a type that enhances the nutrient content and can also alter the soil's physical structure. Greensand is another option which is used when the soil is retaining too much moisture.

Compost, perhaps one that you are already familiar with, falls under the category of soil amendments. It boosts nutrients and improves drainage in heavy clay soils. Manure could also come in handy. Just ensure that it is completely decomposed, otherwise the salts or nitrogen ​from the manure can harm young plants.

​Lastly, vermiculite and perlite are two soil amendments worth mentioning. Vermiculite holds more water while perlite holds less. The latter also allows better aeration. So you can choose either accordingly.


​​5. ​Loosen & aerate

Compact and tightly set soil does not allow water to flow easily through the soil. Digging the soil and moving it around periodically loosens the soil and eradicates the excess density.

​This process aerates the soil and creates more space between the particles. Not only does this aeration enable water to seep freely, it also creates an aerobic environment, which is vital for the roots to carry out several biological processes.


​So there you have it. These are the five simplest infinitives you can start with in order to improve the drainage in your raised garden beds.

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