How to Make a Flower Bed on a Cement Floor

It's possible to grow a flower garden even if your only gardening space is covered in concrete. Consider constructing a raised flowerbed over the concrete floor of your patio, driveway or balcony. Providing enough soil and the right cultural conditions without damaging the concrete results in a colorful and productive flowerbed.

Bed Construction

A simple raised bed allows you to contain the flowerbed soil on top the cement floor. Create the sides of the bed from wood planks or bricks. A wood frame requires minimal effort to move if it is ever necessary. Make the frame 10 to 12 inches deep providing enough soil for the flower roots. Although you can place the soil directly on the cement floor, drainage is poor and the plants may suffer from soggy soil conditions. Placing a sheet of wire mesh across the frame’s bottom and then lining it with landscaping fabric holds the soil in place while allowing moisture drainage. Elevate the bed 2 to 3 inches so the moisture freely drains out the bottom.

Soil Needs

Using a loose, well-draining soil in raised beds prevents compaction. Mixtures containing compost, peat, and vermiculite or perlite work well. A bed constructed over concrete is fully dependent on outside fertilization for supplying nutrients to the plants. Initial fertilization with a slow-release fertilizer supplies nutrients to the flowers for the first two to three months after planting. Afterward, monthly applications of a soluble fertilizer replenish the nutrients.

Care

Flowers grown in a raised bed over concrete require similar as those in traditional beds. Keep the soil moist by watering it regularly, but avoid overwatering. Weeds are a lesser a concern on a concrete base, but pull any weeds that do appear. Avoid walking or kneeling on the soil, as this compacts the soil. Rinsing off any concrete surrounding the bed with water regularly helps keep the concrete clean and prevents heavy soil or dirt buildup.

Concerns

Water draining from the bed can accumulate on the concrete surface, creating an aesthetic problem and possibly damaging the concrete. Setting the bed frame on short legs and using a tray, such as a water heater tray, beneath the bed collecting the water helps eliminate these issues. Fertilizer salts leave a white residue on concrete. Using a tray beneath the bed prevents fertilizer and water runoff or rinsing off the concrete around the bed after fertilizer applications minimizes white marks.

References

• University of Missouri Extension: Raised Bed Gardening
• Iowa State University Extension: Creating Raised Bed Planters