Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden. More on Tony O’Neill
In previous posts, I talked about raised garden beds and their benefits. Gardens don’t always have to be ground-level, so many gardeners prefer to use the beds. I’ve gotten some feedback on the posts and a few questions, and I will address one in this post.
Raised beds don’t need a bottom, but you may need to add one depending on specific considerations. Your raised bed might need a base if you have pest problems or experience lots of water in your garden. So really, it’s an automatic yes, mainly because it helps when your raised soil mixes with the dirt on the ground, but it helps to keep your plants safe.
This post will show more on what you need to know about raised beds, their bottoms, and other options you might want to consider instead of placing a simple base.
What is A Raised Garden Bed?
A raised-bed garden is a planting area higher than the surrounding ground’s level. They keep pathway weeds from your garden soil, prevent soil compaction, provide good drainage, and serve as a barrier to pests such as slugs and snails. The sides of the beds keep your valuable garden soil from eroding or washing away during heavy rains. Raised beds seem to be the ideal choice. Some of its benefits include:
- Save time
- Soil development
- Reduces weeds
- Longer growing season
- Deterring Pests
- It is Ornamental
The main aim of building raised beds is to allow you to improve the soil by growing in a custom soil mix that is better than the one already on the ground. The soil used to make the raised bed will usually be lighter, fluffier, hold more water, and have more nutrients.
Because most flowers don’t have very deep roots coupled with a situation where there is a big difference in soil textures between the soil on the ground (hard) and raised bed soil (soft), the roots will grow thicker and denser in the raised mix and become thinner in the existing soil.
Look into which plants you plan on growing and see how well they do in the soil as deep as your raised beds.
Do Raised Beds Have A Bottom?
As mentioned, a raised bed is a box with no bottom or top—a frame. So raised beds usually have nothing on top of or below them. However, for several reasons (usually protection), you may have to put some material in either of these spots.
So, if the raised bed is sitting on the ground with ideal conditions, you do not need to place anything in the bottom of the raised bed. Allowing the existing soil to mix with the soil you add to the bed will improve the rooting of the plants that grow in the bed.
A bottom will only be required if you protect the surface below the raised bed. An example might be if you have severe gopher problems and other pests from below.
In that case, you might want to place/cut wire mesh or screen (hardware cloth) at the bottom of the bed, cutting corners to fit around corner posts to prevent them from tunneling into the bed.
Also, you don’t need to put a hard bottom in your raised beds, but many people use a weed fabric if they have severe weed issues to keep weed seeds from sprouting in the soil already on the ground.
Weed fabric will block weeds while still allowing drainage. Weeds can dig through quite a lot of soil to reach the top, especially if the soil in the raised bed is soft and light (Which is usually how it will be).
You can use almost anything to prevent weeds from making it to the top of your bed, including cardboard and old newspaper.
To guard against poor drainage, you may want to use a more deliberate hard bottom and consider using rocks. Many plants require well-draining soil, so placing stones in the bottom of a raised bed will help create additional drainage space below the ground.
Moisture stress in the soil can cause the root to rot and damage or kill delicate plants. As soil settles over time and becomes compacted, the rock at the bottom of the bed allows space for excess water to drain away from plant roots.
Crushed rock or pea gravel will work well at the bottom of a raised bed to improve drainage, particularly in beds over 18 inches tall or where the bed is in an area of the yard with poor drainage.
Once the raised bed site is prepared, place the crushed rocks or gravel into the framed space. Spread the stone by hand or with a metal rake until you get a uniform depth of 2 to 3 inches across the bed.
Add good-quality topsoil on top of the drainage rocks until it reaches just below the edge of the raised bed. If you’re putting raised bed against your house (or other structure), you may want to put some water-impermeable fabric on the bottom as a slope to direct drainage away from home.
Alternatively, you could use materials that don’t let the water dry out too quickly if you stay in an area with lots of sunlight. Some of them include dry wood, light, or chunks of paper, and these will help retain some moisture while draining the water from the beds so it doesn’t dry out too quickly.
Even with the benefits of drainage rocks and other material in the bottom of a raised bed, regulate the water you give your beds to avoid over-or under-watering.
Check the water requirements on the package included with your purchased plants and follow those instructions. If unsure, follow the rule of thumb to water the plants only when the top 1 to 2 inches of soil feel dry.
Keep in mind when placing anything at the bottom of the bed the length to which the roots of your plants may grow.
If your plants are going up to a certain point, plan the amount of soil you will put in the raised bed based on that, or you can reduce the amount of the things at the bottom so that the roots can get into the existing soil.
Alternatives to Raised Beds
If, for some reason, you don’t want to compromise your garden by putting a bottom; you can always use these other methods to plant. They all have advantages and disadvantages, so consider everything necessary before starting.
Elevated raised bed gardening.
Gardening in elevated raised beds is a hybrid gardening technique, and it’s a mix of container gardening and raised bed gardening. Think of it as a raised bed on a platform rather than ground soil.
Soil is placed in a container similar to what it would look like simply as a raised bed, and you can garden as usual. This will help you let go of such issues as gofers.
So you elevate your bed so some pests can’t get to it again or wouldn’t want to as it’s in the open.
Traditional bed gardening
Planting directly in the ground may be the easiest way to start your garden if you have a large, full-sun garden plot with rich, well-draining soil.
However, if your garden site has compacted clay or very sandy or rocky soil, you can spend the time and effort to improve it by adding a lot of organic material.
This is the same as what you do to the soil of a raised bed, which is to get the soil fit for planting in the first place. If your soil is already good, you can save time and work on it as it is.
It all depends on the area and conditions where you place your raised bed, so you may or may not need to put a bottom in your bed.
If you have severe pest problems, irrigation issues, weed issues, or other considerations, you may want to put the bottom to prevent all of them from giving you concerns and disturbing plant growth.
If it fixes your issue, it could be wire mesh or screen (hardware cloth), rocks or gravel, paper, wood, or anything else. Also, consider the plants you are growing, and make sure placing a bottom in your raised bed won’t do more damage to your plants than the other reasons you put a base.