Setup
How to Fill a Raised Garden Bed Cheaply
Fill the lower part of a deep bed with free organic material such as logs, leaves and wood chips, and buy good soil mix only for the top 10 to 12 inches.
| Layer | Depth | What to use |
|---|---|---|
| Base | Single layer | Wet cardboard over grass, or hardware cloth if pests dig |
| Woody layer | 6 to 8 in | Logs, then branches and twigs |
| Green and brown layer | 4 to 6 in | Shredded leaves, grass clippings, straw, spent plants |
| Growing layer | 10 to 12 in | Topsoil, compost and aeration mix |
| Top dressing | 1 in | Finished compost, added at planting |
Layering a deep bed
A bed taller than about 12 inches holds more space than vegetable roots need. Lettuce barely uses the top 6 inches, and even tomatoes do most of their feeding in the top foot. So the lower half of a 24-inch bed can be cheaper material that rots slowly and holds moisture.
Start with whatever goes on the ground: cardboard over lawn, or mesh if gophers are a problem. Our bed bottoms guide compares those options.
Next, lay the largest logs flat, then fill the gaps with branches and twigs. Over the wood, pile 4 to 6 inches of soft material: shredded leaves, grass clippings, straw, or old plants from last season. Soak the bed with a hose after each layer. Dry layers create air pockets and settle unevenly later.
Finish with at least 10 to 12 inches of your growing mix, then an inch of compost on top. If you're only filling a 12-inch bed, skip the filler layers and use soil mix for the whole depth.
Free fill materials
Much of the bottom half can cost nothing if you plan a few weeks ahead.
- Fallen leaves. Shred them with a mower first so they don't mat. Bag them up each fall to use in spring.
- Logs and branches from storm cleanup or your own pruning. Hardwood lasts longest.
- Arborist wood chips. Many tree services will drop a load for free. Use them in lower layers only; raw chips mixed into the root zone tie up nitrogen.
- Grass clippings from lawns that haven't been sprayed with weed killer. Spread them in thin layers so they don't turn slimy.
- Straw, not hay. Hay carries grass and weed seeds.
- Sod you dug out for the bed. Flip it upside down in the bottom layer.
- Municipal compost. Some towns give it away at the transfer station.
- Spent potting soil from last year's containers, which can go into the middle layers.
Ask where any manure, clippings or hay came from. Some broadleaf herbicides survive composting and will damage tomatoes and beans for a year or more. To save on the frame too, browse these low-cost bed ideas.
How much to buy
Work out the full volume first, then subtract what you'll fill for free. A 4x8 bed that's 24 inches deep holds 64 cubic feet. If the lower 12 inches is logs and leaves, you only buy 32 cubic feet of growing mix, about 1.2 cubic yards instead of 2.4.
For the growing layer itself, a common mix is 60% topsoil, 30% compost and 10% bark fines or perlite. The soil mix page lists bag counts for common sizes.
Order about 10% extra if you're buying bulk. Loose soil compacts when it's watered, and a little left over is handy for topping up. Above roughly one cubic yard, delivered bulk soil almost always costs less than bags.
What not to fill a raised bed with
- Plain native clay. It packs down and stays waterlogged inside a frame.
- Only bagged potting soil. It's light, pricey, dries out fast and shrinks a lot.
- Rocks, gravel or broken pots "for drainage." They hold water in the soil above.
- Treated or painted wood scraps, pallets of unknown origin and old railroad ties.
- Black walnut branches, leaves or hulls.
- Plastic, bottles, foam or other trash used to take up space.
- Fresh manure in the root zone. It can burn roots and may carry pathogens.
- Diseased plants or weeds that have set seed or spread by roots.
- Fill dirt from construction sites. It's usually subsoil with no organic matter and may contain debris.
- Pet or human waste and meat scraps.
Letting it settle
A layered bed shrinks as the organic layers break down. Plan for the surface to drop several inches in the first season, and more in a deep bed full of wood. A bed filled with soil mix alone typically settles 2 to 3 inches.
You can speed up settling before planting. Soak the bed thoroughly, let it drain for a day or two, then add more mix to bring the level back up. Doing this twice before you plant makes a big difference.
Fill an inch or two above the rim at first if you like; it will come down. After the first year, a yearly layer of compost usually replaces what the bed loses. If the surface sinks more than 3 or 4 inches, add soil mix in the fall so it can settle over winter.
How to choose
Bed 12 inches or shallower
Skip layering. Fill the whole depth with a good soil mix.
Bed 18 to 24 inches deep
Use logs and leaves in the lower half and soil mix in the top 10 to 12 inches.
Tight budget, lots of trees
Collect leaves and branches in fall and build in spring, buying only the top layer.
Planting this weekend
Use soil mix for the full depth now. Layered beds keep sinking for months after you build them.
Related guides
What is the cheapest way to fill a raised bed?
Use free logs, branches, leaves and wood chips in the bottom half, and buy only the top 10 to 12 inches of soil mix. Bulk soil costs less per yard than bags.
Can you plant right after filling a layered bed?
You can, but expect sinking as the layers break down. Water it deeply and top up the soil once or twice first. Building in fall gives the layers time to settle.
How full should a raised bed be?
Once settled, the soil should sit an inch or two under the top edge. That keeps water and mulch from washing over the sides.