Best Size For Raised Garden Beds

January 10, 2022

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For homeowners that have poor soil, an uneven lawn, or can’t bend over, a raised garden bed is the perfect solution. A raised bed garden is a simple frame that is built on top of the soil to hold it above ground. There are many benefits of raised bed gardening, like easy access to plants and greater control over growing conditions. When you build a raised bed, you can amend the conditions for the plants you are growing, provide better nutrition, have less erosion, and improve yield.

About Raised Bed Gardening

A raised bed is not the same as a garden container or planter. This is a frame, typically made built of wood or other bed materials, without a bottom. This allows for better drainage into the natural, good soil and leaves enough room for plant roots to extend. Garden containers and plastic planters, in comparison, have bottoms to contain all the soil and are able to be moved. Raised beds must be disassembled and rebuilt when moved. You can build a raised garden yourself easily and can create any size out of a variety of materials, or they can be purchased. A raised bed is the best option if you don’t plan on moving your vegetable garden any time soon.

Why are raised beds better than a ground-level garden? Gardeners prefer the ability to create their own bed with the soil and compost of their choosing that their plants need, creating a new level of control (plus, it’s better on their backs!)

The advantage of the beds raised higher, above grade, keeps the soil in the bed warmer, extending the growing season for your plants that are in a raised bed, which can lead to a higher yield. The space in the raised bed is entirely devoted to plants and, because you don’t need space to walk between them, you can keep the soil loose, which is better for drainage and plant growth. The high wood sides of the bed provide protection against common garden pests and prevent grass, weeds or weed seeds from encroaching on the gardening space.

Best Size For Raised Beds

It’s best to build a raised bed out of pressure-treated wood as it’s rot-resistant. When thinking of building a raised bed, there are some things to consider size-wise:

Width

A reason for raised beds is to eliminate the need for gardeners to walk through them. Gardeners can easily be able to access the bed from all sides. To achieve this, raised beds should be 4 feet wide for children and 4 feet wide for adults. Surpassing four feet in width would make for a bed that is too deep, making the centre become unreachable. If considering wheelchair access, the raised beds should be 2 feet wide for children and 3 feet wide for adults.

Length

The length of the raised garden bed is not as critical as the width. But very long raised beds can be an annoyance to walk or workaround. While the length of raised beds will be determined on available materials, the cost of wood increases more if the length exceeds 12 feet long.

Height

The higher the bed is made, the more garden soil will be required to fill it. This will add to the cost of labour and of the garden project itself if there is that much soil. Raised planters can be built 10 inches deep, but are elevated off of the ground on legs or concrete blocks. Raised garden beds on concrete blocks are ideal for wheelchair access and save you money on imported soil, but can create unhappy shallow roots in that depth. These blocks must be strong enough to hold the weight of the soil when it is wet and allow the water to drain. This is not a favourable situation for vegetables like root vegetables that like depth.

Other considerations of hight to think about:

More garden crops require soil at leash 10 inches high from the bottom to thrive. If the raised bed height is lower than this you will have to till the soil beneath the raised bed.
Many gardeners have found that if the raised bed is on a hard surface, the recommended height of 10 inches of soil may not be deep enough for some crops.
Young children need beds that are closer to the ground.
Beds made for wheelchair access should be 24 inches tall.
A bed that is 36 inches off of the ground avoids excessive bending over.
Consider having a mix of bed heights if you want to accommodate different gardeners.

Some other things to consider about your raised garden beds:

Paths – If you desire to have multiple garden beds, they should be laid out in a pattern that allows access to a central route from one end of the garden to the other. If this collection of beds are for multiple people, a wider central path provides room for access and gathering for everyone. If the garden is large enough, multiple paths will be even more useful. If access is needed for a small vehicle, a path that is at least 10 feet wide is best. For gardeners in wheelchairs, a minimum of 12-inch paths will be needed between raised beds. If there is more space available and there are multiple gardeners working at the same time, 18 to 24-inch paths are more ideal for comfortable access. To have enough room for any sort of cart, wheelbarrow or wheelchairs, give at least 4 feet between the beds.

Orientation – the orientation of raised beds isn’t usually any kind of issue as long as there is an adequate amount of space between the beds for access. Taller crops will cast shade onto the lower crops that sit behind them if they are planted in the same bed. Taller crops will shade lower crops in nearby beds if they are planted in an east-west orientation and the beds are too close together. If it is possible, it is best to position your beds in a north-south direction.

Irrigation – nutrient-rich soil and compost are needed for your plants to thrive in your new raised beds, but the irrigation system is something to keep in mind when planning the layout of them. Drip irrigation is easier to install when your beds are in an orderly pattern, usually a straight line. Overhead sprinklers can be placed to cover your garden layout, but they work best if your raised beds are in a circular, rectangular or square pattern. For those who prefer to hand water, a layout with uniform bed spacing will make this easier as it could help with dragging a hose throughout your garden.