How to Counteract the Effects of Concrete in a Garden

Offsetting Temperature

• When exposed to sunlight, concrete surfaces dry out and heat up more quickly compared to bare soil or garden beds covered in mulch or vegetation. Shading concrete is the easiest way to prevent excessive heat buildup of air and soil in a landscape. Shade trees, hedges, awnings and leafy vines all act to block the sun's rays across the day, slowing or preventing the buildup of heat in the concrete. The negative effects of higher temperatures are notable year-round. In winter, the concrete's warmth causes faster melting of snow or the appearance of new plant growth. In summer, hotter temperatures require more watering of plants to prevent wilting.

Amplified Light

• Light-colored concrete reflects sunlight -- both visible light and infrared radiation. Bounced sun rays off of white concrete driveways and walls can increase air temperature, fading of materials and scalding of vegetation. Painting the concrete, roughing the surface and shading the concrete all diminish the amount of sun energy reflected in the garden.

Water Runoff

• A large expanse of concrete, such as a driveway or patio, is impermeable to rain and leads to lots of runoff. If the concrete area is not graded properly, drainage of the water from the area can cause flooded areas or soggy soils that lead to plant decline or other undesirable effects such as soft soil or habitats for mosquitoes. If wet soil areas arise on the edges of large concrete areas, create a French drain or a trench filled with coarse gravel to capture the runoff without causing soft, muddy pockets. Alternatively, plant wet-soil-tolerant vegetation in the runoff zone where soils remain mucky. More elaborate and expensive drainage systems may also be added to the landscape to shed water more efficiently.

Soil pH

• The runoff and long-term leaching of the salts in concrete causes adjacent soils in the garden to increase in pH. Not all plants tolerate alkaline soils; those less able to grow in alkaline conditions quickly develop yellowing leaves and stunted growth because of a lack of nutrients. Iron and magnesium are two nutrients that are less available to plants in high-pH soil. Offset the issues of higher pH in the garden by planting alkaline-tolerant plants adjacent to the concrete and plants that prosper in neutral and acidic soils farther away. Lower the soil pH next to the concrete with the use of acid-forming mulches and additives containing sulfur, ammonium or aluminum. Large-scale changing of soil pH is expensive and a long-term endeavor.