Constructing Raised Beds

Raised beds are gaining popularity because they are easily customizable. You can determine how big to build them, what to use to make them with, and mix the filler soil to your specifications.

Determine the Raised Bed Size

Build whatever size beds work for your yard and needs, but keep it no more than four feet wide so you can easily reach the center to tend to plants. Standard heights range from six to 24 inches tall. Shallow beds are cheaper to fill, while deeper beds are easier on your back.

Decide on Construction Materials

Lumber is commonly used to build raised beds, but you can also use non-wood materials. Your choice depends on your budget and the materials available. Choose weather and rot-resistant material sturdy enough to contain the soil once you fill the bed.

Common construction materials include:

  • Western red cedar since it is naturally rot-resistant. White and yellow cedar and juniper are also good choices.
  • Pressure-treated lumber is safe if treated with ACQ. Avoid using lumber treated with other chemicals.
  • Non-wood materials like cinder blocks, bricks, or synthetic lumber.

Many people like the look of corrugated metal beds. The metal is safe, but keep in mind it does absorb energy from the sun, raising the temperature of the soil. High soil temperatures can be damaging to your plant’s root systems.

Do I Need to Remove the Grass?

Whether or not you remove the grass at the bottom of the bed is a personal choice. Removing it will help keep grass from sprouting up through your flowers, but it also adds more work.

The best ways to remove grass are to spray it with a non-selective herbicide that kills everything it contacts, or dig it up with a shovel. If you choose not to remove it, lining the bottom will help grass from growing up from the underlying soil.

Do I Need to Line the Raised Bed?

This question will get different answers depending upon whom you ask. The truth, though, is there are many more advantages to lining the bottom than disadvantages. Installing a liner between the ground and the soil you add keeps rodents from entering the beds from underneath, helping to prevent weed growth, and may insulate the bed, keeping its soil warmer.

You can line your beds with cardboard, weed block, landscape fabric, or newspaper. Remember that these materials break down over time, so they aren’t permanent fixtures.

How to Fill the Raised Bed with Soil

You can fill raised beds with topsoil, but it’s best to mix topsoil and compost or fill it with potting soil.

Filling it with topsoil is the cheapest, but you can improve fertility and drainage by amending the soil. Mixing 50% topsoil and 50% compost keeps the soil light and enhances the structure.