How Tall Should Raised Beds Be?

Finding the perfect height?

Using raised beds is a great way to grow vegetables, helping you to better control your conditions especially if you have poor quality or lack of topsoil. They are also excellent for accessibilty as you don't have to reach all the way down to the ground for harvesting and maintaining your crops. With all the benefits that raised beds provide, the question 'how tall should a raised bed be?' is one that is important to consider when you are creating or upgarding your garden. 

The most common depths of raised beds range between 15 and 60cm (6-24in), but the best answer for your situation depends on a number of factors. Generally, deeper is going to be better, but it’s worth bearing in mind that the deeper the bed, the more compost you’ll need to fill it, which can be costly.

Firstly, it’s important to consider where the bed will be placed and what the ground beneath is like. If you have good topsoil, then a raised bed with a height of 30cm (1ft) is likely to be suitable for growing most plants. If you have poor, or compacted soil, or indeed if you are growing on top of concrete, then more depth will be required and you will also need to think about drainage. The Royal Horticultural Society (RHS) recommends that raised beds on top of hard surfaces have a depth of at least 45cm (18in), but ideally 60cm (2ft), so that plants can root deeply. This will also reduce their watering needs as the extra depth allows more water to be retained through drier periods. 

Image: My raised bed garden in late June

Next, think about any needs you have. What height bed would be easiest for you to manage if, for example, you have back pain or limited mobility? Consider not only the soil height, but the eventual height of any plants that you intend to grow. If you use a wheelchair, a raised bed with space below can be useful.

You should then consider the depth requirements of your plants. In my book, Grow Food For Free,  I recommend using wood from pallets as a low-cost way of building raised beds if you need something usable as quickly as possible for as cheaply as possible. In the book I use the number of planks as a measurement for the depth of a raised bed in relation to the type of crops you can grow in that bed. For context, the width of a pallet plank varies but is usually around 10cm (4in). 

One plank can be deep enough to grow vegetables like lettuce, spinach, chard, radish and beetroot. Two planks’ depth is suitable for smaller carrots, onions, strawberries, perennial herbs, and beans. Three planks for brassicas, potatoes, carrots, leeks, rhubarb, and jerusalem artichokes. And four planks for deeper rooting shrubs such as blackberries and gooseberries. Whilst these depths aren’t the optimum recommendations, you will be able to enjoy decent harvests from surprisingly shallow raised beds.

Image: Harvesting onions from a raised bed

Angelo Eliades at Deep Green Permaculture points out that most vegetables are fairly shallow-rooted, and have 80% of their roots in the first 30cm (1ft) of soil, so they can be grown in a raised garden bed that contains 40cm (16in). Culinary herbs such as thyme, oregano, marjoram, and mint also have quite shallow roots.

Landscape Designer Darcy Larum recommends raised bed depths of 12 to 18 inches (31-46 cm) to grow arugula, broccoli, brussels sprouts, cabbage, cauliflower, celery, corn, chives, garlic, kohlrabi, lettuce, onions, radishes spinach, or strawberries. 18 to 24 inches (46-61 cm) for beans, beets, cantaloupe, carrots, cucumber, aubergine, kale, peas, peppers, squash, turnips, and potatoes. And 24 to 36 inches (61-91 cm) for deep rooted vegetables such as artichoke, asparagus, okra, parsnips, pumpkin, rhubarb, sweet potatoes, tomatoes, and watermelon.

Height & pest control

A final thing to consider is whether the height of your raised bed can help prevent pests. Carrot flies rarely fly above 50cm (20in), so higher beds can help to protect your carrot crop. A height of more than 60cm (2ft) is said to help deter rabbits, and can also help prevent damage from enthusiastic dogs! 

These 30cm (1ft) tall raised beds are tall enough to help guide ducks through your garden rather than over your garden!

On the subject of animals, you may be considering the use of ducks as natural slug control in your garden. From natural experience I have found that raised beds above 30cm (1ft) in height are enough of a barrier to put off ducks jumping up and onto beds the majority of the time. Instead, they are happier going inbetween the paths and around the garden boundaries looking for slugs rather than attempting to hop on and off raised beds. 

My thoughts

From experience creating a new garden on top of hard stone, I have been able to successfully grow most annual crops in 30cm (1ft) high raised beds which I believe is the best all-rounder if you are looking for a quick answer. I understand that this contradicts the RHS advice for bed depths on hard ground but I know as a fact 30cm is suprisingly successful. Yes, perhaps some crops may have benefitted from deeper beds, but even the raspberries are yielding well, so don’t be put off by having to choose extra deep beds because they will require a huge volume of material of food.

If you are looking for beautiful raised beds that provide plenty of rootspace for all crops, the 43cm (17in) tall vego garden raised beds are the go-to range for long-lasting beds that will help you grow an abundance of food.

Image: 43cm (17in) tall vego garden bed