How to Build a Raised Garden Bed (2024)

FAQs

How to calculate amount of soil needed for raised garden bed? ›

Remove all rocks, old roots, and plant debris. Dig down a little further with the shovel (a few more inches) to just loosen up the soil. Mix the soil with organic matter such as compost. We recommend that the compost make up about 25% of your soil.

Ideally, the site will not be shaded by trees or have competition from tree roots in the soil. Remove grass in the location before adding soil to the bed. The ideal width of a raised bed is 3-4 feet so that veggies will be within arm's reach from either side.

For a 4x8-foot raised bed with a 6” height, using Mel's Mix: about 5 cubic feet each of compost, peat moss, and vermiculite is needed. It usually takes about two to three bags of purchased fertile mix (1.5 cubic feet each) to cover the bed surface to a depth of 2 inches.

Our recommended approach involves layering the bed with a foundation of coarse materials like gravel for proper drainage, a layer of garden soil and garden matter, a layer of compost or well-rotted manure, and a top layer comprising high-quality topsoil. This approach creates a fertile ground for vegetables to thrive.

To fill a 3x6 bed with 10" sides, you will need 15 cubic feet of blended soil. To create the blend, use the following quantities: 9 cubic feet of topsoil (9 20-quart bags) 4.5 cubic feet of compost (4.5 20-quart bags)

A raised bed does not always require a significant depth for it to be effective. They should have at least 8 inches of soil depth to accommodate the root systems of plants, because the majority of plant roots require 6 – 8 inches of soil for healthy root growth.

Use the Lasagna Garden Method

To start, lay down sheets of cardboard or newspaper for weed suppression and then fill the raised bed structure halfway up with alternating layers of nitrogen-rich materials (like kitchen scraps and grass clippings) and carbon-rich materials (like wood chips and dried autumn leaves).

Soil taken from your yard or a garden bed is too dense to use in a pot or raised bed. Instead, for containers, you'll want to use potting mix (also called potting soil), a lightweight and fluffy alternative. For raised beds, you'll want to use a blend of potting mix and garden soil.

To put it simply, you should put a layer of organic material at the bottom of your garden bed, which will break down and enrich the soil. This can include compost, or woody material such as logs, dry wood, branches, and leaves.

What is the best soil mix for vegetable gardens? ›

Gardening magazine's trial of the best soil mixture for raised beds found that a blend of 50% topsoil, 25% coarse sand and 25% compost was best.

The cons of raised beds

The soil mix also can be a significant, albeit one-time, expense. Raised beds need water more often since the soil is more exposed to air and dries quicker. Similar to growing in containers, the extra watering can leach nutrients out of the soil quicker than in-ground gardens.

Tomatoes should ideally be grown in a raised bed that's at least 15 to 18 inches deep. Many of my clients in Houston are successfully growing tomatoes in 12-inch deep raised garden beds, but their plants tend to be a little stunted compared to plants in deeper beds.

As a general rule, put tall veggies toward the back of the bed, mid-sized ones in the middle, and smaller plants in the front or as a border. Consider adding pollinator plants to attract beneficial insects that can not only help you get a better harvest, but will also prey on garden pests.

On average, a DIY raised bed constructed from wood will cost $25 to $50 per square foot. To have a wooden raised bed constructed and installed for you, budget for at least $100 per square foot. (Find a kitchen garden company in your area.)

They should have at least 8 inches of soil depth to accommodate the root systems of plants, because the majority of plant roots require 6 – 8 inches of soil for healthy root growth. A depth of 8 – 12 inches will suffice for most gardening situations.

It's best to use untreated wood to build your raised garden beds, preferably a type of wood that won't decay quickly, such as cedar, redwood, or hemlock. Both the type of wood that you might find for sale and its affordability will vary based on where you live.

In general, eight inches is a good minimum depth for raised garden beds. If there are issues with drainage, or the plants in the box are sensitive to excess moisture around their roots, additional depth can help by allowing water to seep naturally.