Raised bed gardening is different from traditional in-ground gardens. (Forgive me for stating the obvious.)
Your soil mix matters more because it’s in a contained environment, meaning plant roots can’t reach deep into the earth to extract extra nutrients.
With this in mind, let’s talk about creating a soil blend that will adequately feed your plants in your raised bed garden.
The Basic Formula
Success in raised beds starts with a simple ratio:
- one-third topsoil,
- one-third compost,
- and one-third aeration materials.
This is going to strike the right balance of nutrients, moisture retention, and drainage that plants need.
Let’s look at each of the components a little closer….
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Topsoil: The Foundation
Good topsoil forms the backbone of your mix. Look for screened topsoil that’s free from debris.
Quality topsoil should have a dark, rich color. While bagged topsoil from garden centers works fine, consider buying in bulk.
A trusted landscape supplier often provides better quality topsoil at a lower price.
Watch out for topsoil that’s heavy with clay or sand. Neither of these extremes works well in a raised bed.
Compost: The “Food”
Compost adds vital nutrients and beneficial microorganisms to your soil. You can use either homemade or store-bought compost.
Homemade compost usually offers better quality if done right. The best compost includes both “brown” materials (leaves, straw, paper) and “green” materials (grass clippings, kitchen scraps).
How can you tell if compost is ready? It should smell earthy and look dark and crumbly. If it smells bad or you can still recognize the original materials, it needs more time to decompose before you add it to your raised bed.
Aeration Materials: the Structure
The final third of your mix needs materials that keep soil loose and well-draining.
You have several options:
- Peat moss provides excellent water retention. (However, it’s slow to renew environmentally.)
- Coconut coir works similarly to peat moss. (It’s becoming more popular because it’s more environmentally friendly.)
- Vermiculite helps with both drainage and water retention. (It costs more but lasts longer.)
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Common Problems and Solutions
Watch for these signs of soil problems:
- If water pools on top of the soil’s surface, add more aeration materials.
- If water runs straight through the soil, increase organic matter.
- When soil becomes compacted, as it inevitably will throughout the season, work in additional coconut coir or vermiculite as needed.
Your plants will tell you what they need. For instance, yellow leaves often mean nutrient deficiencies.
Wilting between waterings suggests poor water retention (aka – it’s draining too quickly, so you need more organic matter).
Be a student of your garden, and it will reward your efforts!
Cost-Saving Tips
Starting multiple beds? Buy materials in bulk.
I’m all about pinching pennies, but don’t be tempted to skimp on quality topsoil and compost. Soil will make or break your gardening success.
Choose less expensive aeration materials. Pine bark fines cost less than vermiculite and work almost as well.
Check out more tips for filling raised beds cheap here.
Also, start collecting compostable materials in fall. Leaves and organic matter are free and plentiful around that time.
In fact, we have a quick video about that:
Remember: good soil is an investment in your garden’s success. Take time to create the right mix from the start!
