How to Build a Concrete Block Raised Bed Garden

 How to Build a Concrete Block Raised Bed Garden

Use concrete blocks to create a raised bed and fill it with good garden soil. It's quick, easy, and lasts forever. The 4' x 4' raised bed is large enough to grow all the produce to make fresh spaghetti sauce and freeze, or make a few jars for the winter.

Note that the blocks are 7 inches wide and 9 inches long, so the bed will not be 4 x 4 inches. The block bed is 55 inches long, which comes out to about 4 1/2 inches. The interior garden is 3 1/3 inches or about 40 inches wide on the inside. We built this to replace a wood frame raised bed, the concrete bed is a little short on space.

How to Fill the Raised Bed

If you have some time to turn the bed on before you plan to use it, follow these instructions.

First, cover the ground with layers of newspaper to kill any weeds and discourage weed seeds. This newspaper layer can also be recycled into office paper or cardboard. Use what you have. We also added rotted boards from the raised bed that was replaced. The key is to overlay everything, so make sure the content overlaps. If you are using paper, make sure there are several layers.
Water under the paper.
Next, apply a layer of the brown and green material as you would when building a compost pile. Add more "brown" carbon-rich material than green. To use a nitrogen-rich “green” material, apply thin layers of wet food and cover with dry material.

Alternate Method: Mixing and Dumping

If all those crazy layers are like making lasagna and taking up too much of your valuable time, mix everything up in your wheelbarrow and toss it on the raised bed. Use the thicker material on the bottom. Cover the plants with prime soil to give them a good start.

Green and Brown Compost Explained

Carbon-rich "brown" materials are shredded leaves, wood ash, straw, sawdust, shredded newspaper, and wood chips.

“Green” nitrogenous materials are fresh or green materials, such as kitchen scraps, coffee grounds, watermelon rinds, and corn husks. Add apple peels, egg shells, vegetable peels, and that creepy green thing to the back of the crisp drawer.

How to Collect These Materials

Grass clippings contain as much nitrogen as fertilizer. The bed is manufactured a year before it is used. Start in late summer and fall, when there is an abundance of vegetable clippings, grass and leaves.
Keep a covered container in the kitchen for food scraps during canning and preserving season. Ask cafes for basics. Discard hairbrushes, dryer lint, paper towels, and egg cartons when cleaning. Also keep the nut shells.

What if I want to use the bed right away?

If you're making a bed for immediate use, start with thick layers of paper, cardboard, and shredded office paper, then water. I replace the bed with good garden soil. That soil will go back into the new concrete block layer. I also include compost and shredded leaves

Starting from scratch, use about 40% peat or pulp. The pulp contains fewer nutrients, holds more water, and is less acidic. Add moist Canadian sphagnum moss or mulch to the raised bed. Add a mixture of packed soil, animal manure, sand, perlite and vermiculite.
If you use some garden soil, sterilize it first. This will prevent you from transferring weed seeds, insects, and soil-borne diseases to your new raised garden. Bake the dough on cookie sheets at 200°F for 20 minutes, stirring once about halfway through.
Cover the bed with the best enriched gardening soil for planting.
Enrich your “new soil” with a slow-release fertilizer. Or add (N) "nitrogen", (P) "phosphorus" or (K) "potassium", by adding (N) blood meal, (P) bone meal, and (K) green sand.

Other Additions to Nourish Your Raised Bed

Potting Mix Items: Materials commonly used to make potting mix can also be added to a raised bed. Soil additives include peat moss, vermiculite, sand, perlite, pulp or compost.

Soil Supplements: Soil supplements are used to retain moisture, making water available to plants. These materials are able to lighten and aerate the soil. Clay soil can benefit most from materials that retain moisture and loosen the growing medium.

Coir: Coir is sold as a peat substitute and soil amendment. It will also loosen garden soil in raised beds or containers. Like peat, it retains moisture in the soil and improves drainage. Coconut is a renewable resource. Peat comes from bogs that took millions of years to form and are disappearing quickly.

Scraps and Other Organic Matter: Bury food scraps, shredded paper, dust bunnies, and dryer lint when making beds. Be creative, do something new. Suitable organic matter includes the sad green matter found in brittle, old cotton socks.

What to Plant in the 5" Square Border Containers

The nasturtium, the “sun cup,” is located at the edge of the raised bed in the photo above. Flowers in the garden attract pollinators and provide soil cover to prevent weeds.
I think the 5 inch square borders in the concrete blocks are a bonus. Will the smaller 5 inch squares be warmer or cooler than the raised bed? I'm going to try a raised bed of herbs.

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