9 Raised Bed Mistakes to Avoid this Season

Whether you’re working with a yard filled with rocky soil or looking to limit some of the reach and bending associated with tending a garden, raised beds are a great tool. The excitement makes it easy to rush to planting, but learning the right way to do things can save you hours of time and headaches.

While there’s nothing quite like learning from your own mistakes, sometimes it’s nicer to learn from someone else’s. In this article, I’ll explain nine of the common mistakes gardeners make when building and growing in raised beds.

Using the Wrong Material for the Beds

In their simplest form, raised beds are a way to make gardening more accessible. They allow you to grow plants in areas with poor soil and make weeding and harvesting less taxing on your body. But building one isn’t as simple as sticking soil in any type of container that will hold it!

One of the biggest issues gardeners face when building beds is using untreated pine lumber. While this type of wood is inexpensive and easy to find in hardware stores, it quickly breaks down with exposure to moisture and microorganisms. Untreated pine can start to crumble after a single growing season in a humid area!

If you want to use wood, rot-resistant options like cedar, cypress, and Osage orange are your best bet. While these boards will be more expensive, they’ll last at least a decade. It’s best to avoid treated lumber since some of the chemicals used to treat the wood harm human health and the environment.

You can also utilize materials other than wood. Metal beds are long-lasting and aesthetically appealing. Plus, thoughtfully designed beds make construction easy!

Choosing the Wrong Type of Soil

When you grow in the ground, the soil is already there. Sure, you may have to amend it with compost, add some fertilizer, and aerate it with a broad fork, but you aren’t starting from square one. But when you grow in a raised bed, you’re looking at a clean slate. Unfortunately, that leaves lots of room for mistakes.

One common mistake growers make is choosing the cheapest material to fill their beds. While generic fill dirt, woodchips, or heavy clay soil may be inexpensive up front, they won’t create the healthy garden they’ve dreamed of.

Another common mistake is using bagged potting soil designed for seed-starting and potted plants. These products contain excellent drainage and a loose texture that helps small seedlings thrive. However, they tend to compact over time and lack the nutrients and structure mature plants crave. Plus, potting soil is often more expensive than suitable alternatives.

The best type of soil is well-draining, water-absorbing, and nutrient-rich. Often, landscaping companies sell pre-mixed soil blends designed for raised bed growing. Another option is to mix two parts topsoil with one part finished compost.

Assuming You Must Fill the Entire Bed with Soil

If you’re using a tall raised bed and looking to save some money, remember you don’t have to fill the entire bed with soil! Adding materials like logs and sticks to the bottom of the bed fills in empty space without breaking the bank. Then, you can add nutrient-rich soil on top of the solid materials.

This practice of building in layers is called hugelkultur. If you use this method, think about what types of plants you plan to grow in the beds. Larger plants like tomatoes and broccoli develop expansive root systems, so they require at least 12 inches of soil. However, smaller plants like lettuce, radishes, and dill can get away with growing in six inches of soil.

Building Beds Too Big

While you can easily walk through an in-ground garden, you should work raised beds while standing or kneeling on the ground outside. Therefore, ensure you can easily reach all parts of your bed while standing on the surrounding ground.

In general, raised beds should be no more than three to four feet wide. Creating a bed that’s four feet wide means you’ll only have to reach two feet from either side. While two feet may not sound like a lot, remember you’ll spend lots of time reaching into the middle of your garden beds! I’ve heard many gardeners tell me they wish they made their beds narrower to make working in them more comfortable.

Another thing to keep in mind is the walkways between your beds. If you’re building multiple beds, leave at least two feet between them. While you may be able to walk through an aisle that’s only a single foot wide, this pathway won’t allow you to comfortably kneel, nor will it accommodate a wheelbarrow or wagon!

Placing the Bed in the Wrong Location

Even if you build the perfect raised bed and fill it with excellent soil, plants will have difficulty growing if the bed receives little sun or is in a low-lying area that regularly floods. If you plan on growing vegetables, herbs, and/or cut flowers, choose a location with at least eight hours of sun.

Along with thinking about the ideal growing conditions, consider convenience and water access. While you may think your design will look great in your sunny front yard, it will be difficult to water if you only have a spigot out back.

Not Smothering Problematic Weeds

While you don’t need to add a bottom to your raised bed, you should keep weeds in mind. It’s easy to think that a foot or two of soil will keep weeds from creeping in, but you may be surprised by the tenacity of plants like bindweed and Bermuda grass!

If you’re putting your beds on top of an area with rhizomatous weeds, take a moment to smother the weeds before adding the best. One option is to place a piece of greenhouse plastic or silage tarp on the area for a month or two during the summer. The plastics will smother the weeds and kill them.

Another option is to add a few layers of cardboard on top of the ground before adding your raised bed. Some weeds can grow through the cardboard as it breaks down, but this is a good option if you’re in a rush to start planting.

Planting Crops Too Close Together

It’s easy to become excited by the possibilities of gardening—especially when you erect a new raised bed in the spring. Enthusiasm isn’t a bad thing, but it can be a mistake if it leads you to crowd too many plants into a small space Rather than planting 50+ plants into a small raised bed, add a few and focus on providing them with excellent care.

Since each plant is unique, look up its mature size and space requirements before planting. You can then use this information to properly space your vegetables and flowers. Leaving enough space between plants is crucial to maintaining appropriate airflow and preventing disease. Plus, it allows each plant to access the water and nutrients it needs.

Building Beds Too Short or Too Tall

As I mentioned above, you can build almost any size raised bed. However, it doesn’t mean you should! Building the right height is just as important as keeping the width and length in mind.

It’s easy to end up building a short raised bed to cut the costs of construction materials and fill soil. While six-inch or ten-inch raised beds aren’t a problem if the native soil is loose and supportive of plant growth, this height is too short if you plan on adding beds to compacted soil or a rocky area.

On the other hand, four-foot-tall beds are often unnecessary for growing vegetables and flowers. Most plants will grow just fine in two feet of soil. So, unless you’re building a tall raised bed to limit bending, there’s no need to construct one this tall.

In general, 12-30 inches is the sweet spot. Short beds work well for most crops, but you can choose a larger bed to make working more comfortable.

Adding a Bottom

Many beginning gardeners make the mistake of putting a bottom on their raised bed to keep weeds out and soil in. The answer is no! Leaving the bottom off the bed open allows excess water to escape and also allows long roots to grow into the native soil.

Additionally, adding a bottom to the bed adds extra costs. Why spend money on unnecessary materials when you can spend it on seeds and plants?