7 raised bed gardening mistakes – and solutions for a healthy vegetable harvest

Raised beds are admired for their ease, which allows gardeners to grow a variety of plants, fruits, and vegetables in spaces of all sizes. However, despite their versatility (and the ability to accommodate a diverse range of greenery), some mistakes are easy to make when practicing raised garden ideas.  

As gardening guru Gardener Scott (and other experts explain), people often assume that a raised garden bed has 'magical properties,' meaning you don't need to maintain it. This couldn't be further from the truth, he says in this video. 'You still need to garden in your raised bed just like anywhere else in the landscape.' 

So what do you need to watch out for so that you boost not damage your vegetable garden ideas?

Raised bed gardening mistakes – according to experts

Whether you're new to the concept or you've already mastered kitchen garden ideas, these common mistakes can occur in any garden. Here's what you need to avoid – and what the experts do instead.

1. Using a wrong-sized bed

Whether you're learning how to grow potatoes or another crop, the size of the bed will make a big difference to your yield – and the ease of gardening in a raised bed. 

'Make it wide enough so that you can reach the entire bed,' explains Gardener Scott. If you want to make the most of a freestanding bed, make it around four feet wide, so you can walk around it and use both sides. 

On the other hand, if your bed is against a garden wall, 'don't do four feet wide' – you won't be able to reach the back, wasting half the bed. 

Height also matters, especially if you have mobility issues (or even a bad back): 'If you have mobility issues or don't like working on your knees, you're free to adjust the height to whatever works best for you,' says Scott. 

2. Skipping the planning stage 

'When you skip the planning stage, you risk placing your raised bed in the shade or facing a sub-optimal direction, reducing sunlight exposure for your plants,' warns Emma Loker from DIY Garden. Instead, knowing how to build a raised garden correctly begins with a careful planning stage. 

The expert recommends positioning your raised bed facing north-south rather than east-west to optimize sunlight exposure. 'Ensure your raised bed location isn't shaded by shrubs or trees before construction,' she adds.

3. Choosing the wrong location for your bed

This one seems simple, but Gardener Scott says many gardeners make this mistake. Garden beds are 'not magical,' he reiterates: they can't 'overcome the wrong spot. If you've put your raised bed under a tree in full shade, and your plants aren't doing so well, it's probably not because they're in a raised bed, but because they're in the wrong location.' 

All vegetables need the sun to thrive, so always choose a sheltered position in full sun for your raised garden beds. And don't forget to position them in a way accessible for your irrigation system or garden hose. 

4. Not leaving enough space between garden beds

It may be tempting to have your garden beds neat and close to each other, but this will make moving between them difficult. Scott advises to leave 'ample room to move your wheelbarrow in', or room to bring in compost and mulch. 

That doesn't mean you need six feet between beds – just a wide enough path to the side of your beds and two feet between them so that you can walk between them easily. Even watering will become 'difficult' if you 'place them too close together', warns Gardener Scott. However, with the right planning, it may be possible to still bring a raised bed into your small garden ideas. 

5.  Using weed killer 

While it may be tempting to use weed killer on (or near) your raised bed, Emma warns that these chemicals can harm your soil for years. Instead, she suggests removing weeds by hand or using a stainless steel hand weeding tool that will not cause long-lasting harm. 

6. Choosing the wrong soil type

This goes back to Gardener Scott's main point about raised garden beds – they're not magical, so 'taking poor soil' from just anywhere in the garden and filling the raised beds with it will give your poor results. 

'As a bare minimum, you need to add some kind of organic material to your soil, like compost,' says Scott, 'and if you can, get a blend that already has compost and nutrients in.' 

You'll then need to keep adding organic material 'regularly' to keep the soil nutritious. 

7. Choosing the wrong material for your bed

Scott admits that he likes wood best but does realize that 'wood will decompose and rot over time, so my raised beds will need to be replaced. Especially if you live in a damp and humid climate, 'you may want to bypass the wooden beds completely' and maybe consider galvanized steel instead. 

Brick and stone are also great solutions – 'materials I don't have to worry about decomposing.' Build your raised beds to last and enjoy a crop of homegrown vegetables yearly.

How deep should raised vegetable beds be?

Raised vegetable beds should be at least 8 to 12 inches deep, however, they can be deeper if you have mobility problems or if soil drainage is poor. In the latter case, you can back-fill the raised bed with a porous growing material. 

Should raised beds be open on the bottom?

Experts are divided on whether it is a good idea to fill the bottom of your bed. The answer often varies on a case-by-case basis. 

'I am in favor of raised beds that are open to the ground in most cases. This way, earthworms and other helpful microbes can make their way into your garden bed more easily, and the ground underneath an open raised bed has ideal natural drainage,' says Erinn Witz, Co-founder at Seeds and Spades. 

However, there are some instances where it is better to close the bottom of the bed.  For example, if you know that the ground under the bed had been heavily treated with chemicals. 'You want to keep substances like that out of your garden as much as possible, and a closed bottom helps with that,' Erinn says. 

What do I put on the bottom of a raised garden bed?

You can fill the bottom of a raised garden bed with a number of organic materials, including straw, grass clippings, wood chips, and leaves. Place cardboard – or any suitable weed barrier material – over this organic layer, weighing it down with a few bricks or pegs. This will allow the organic material to turn into rich compost, into which you can mix soil for a rich growing environment. Usually, you would aim for a mix of 30% compost, 60% topsoil, and 10% potting soil – the latter will help drainage.