How to Create the Best Soil for Raised Beds for Healthier, More Productive Vegetables

Growing vegetables in raised beds offers many benefits. Raised beds give your garden a sense of scale and structure, limit the presence of weeds in beds, and are easier on the body as they require less bending. But unlike planting directly into the ground and amending existing soil, you'll need to fill the beds with soil yourself. Choosing the right soil will determine how successful the vegetables growing in your raised beds perform. To help guide you, we consulted gardening experts who shared their recommendations for the best soil to use in raised beds for optimal plant health. 

The Best Soil for Raised Vegetable Garden Beds

A raised garden bed allows you to provide your plants with the type of soil they prefer. And while the specifics vary depending on what you're planting, there are some general characteristics that are always desirable. "A good potting soil should do three main things: hold moisture, drain well, and provide nutrients," says gardening instructor Meg Austin.

The structure of the soil is also important. Master gardener Angela Judd likes a crumbly, well-aerated soil that drains but doesn’t dry out. "Aim for a mix that wets easily and holds moisture," she says. "Active microbes, fungi, and worms [will] cycle nutrients and build structure." She recommends aiming for moderate soil fertility. "Steady, slow-release nutrition rather than heavy, salty inputs," Judd says. "Excess manure can push salinity too high."

The best raised bed soil usually isn’t something you buy in a single bag; it’s something you build over time, Austin adds. "Start with a base of raised bed soil, then mix in compost for nutrients and structure," she says.

Useful Soil Combinations for Raised Beds

When filling raised beds, Austin recommends avoiding topsoil, as it compacts too quickly. Instead, she recommends a mix that is about 60 percent raised bed soil, 30 percent compost, and 10 percent other organic material. "Raised bed soil is usually a blend of lighter ingredients like peat moss or coconut coir for water retention, plus materials like perlite or bark to keep it airy and well-drained," she says.

Judd agrees that using only potting soil or only compost can cause problems in raised beds. "Potting mix collapses over time and can repel water; straight compost stays too wet, shrinks, and can be salty," she explains. She recommends using equal parts high-quality compost, vermiculite or perlite for aeration, and coconut coir as a more sustainable alternative to peat moss.

Tips for Creating the Best Soil for Raised Beds

By combining best practices and avoiding common mistakes, you can create the ideal soil for your raised beds. Here are a few tips to get you started:

Test Your Soil

A simple soil test will tell you the pH of your soil and the nutrients it's lacking, so you can add the right amendments. "A near-neutral pH of 6.2 to 7.2 is ideal for most vegetables," says Judd. 

Protect the Surface

Judd suggests adding a 2- to 3-inch layer of mulch, such as shredded leaves, straw, or chipped wood, over the soil to lock in moisture, help regulate the temperature, minimize evaporation, and feed microbes. "Keep living roots in the bed as much as possible, and use cover crops between plantings," she says.

Choose the Right Amendments

Creating a new bed from scratch gives you the chance to start the plants out in optimal conditions. Judd suggests considering the following amendments for your newly installed beds.

• Worm castings: A byproduct produced by worms as they break down organic materials, Judd says. Worm castings are the secret to her successful vegetable garden. She recommends adding a 1/2- to 1-inch layer on top at planting.
• Organic fertilizer: Use a gentle, balanced blend of organic fertilizer to encourage plant growth. Just recommends mixing 4 to 6 inches into your soil, depending on the label's recommendations.
• Rock dust/basalt: Basalt is an aphanitic extrusive igneous rock that is rich in iron and magnesium. A light sprinkle over your beds will add a boost of micronutrients.
• Mycorrhizae: These are fungi that benefit the roots of many plants. Judd recommends dusting mycorrhizae over transplant roots or planting holes to increase establishment.

Don't Choose Based on Price

Austin notes that one common mistake when choosing soil for raised beds is grabbing the cheapest bag on the shelf and assuming all potting soils are the same. "Some mixes are heavy on fillers like sand or bark, which dry out too fast or compact quickly." Other mixes are overloaded with synthetic fertilizers that give plants a quick boost but leave them hungry later, according to Austin. "The best soil isn’t necessarily the priciest bag either, it’s one that’s light, drains well, and has plenty of organic matter."