Black Slime Mold on Soil

Molds love shade.

When Aprils showers bring May's flowers they also deliver perfect conditions for slime molds, also spelled mould, to form on soil, grass and plants. Slime molds are fungus organisms. They thrive in damp, shady places like the surface soil of lawns, and organic compost and mulch. According to the Dirt Doctor, slim mold is mostly an aesthetic issue. There a few simple and environmentally friendly things you can do if this pesky spring visitor plagues your yard.

Identifying slime mold

Splotches of color

Recognizing slime mold is relatively easy. It appears in a range of colors from black-brown, to off white or salmon, brick red, mustardy yellow or orange. Some appear in the spring and look like white-ish bubbles of clay or plaster on lawns and plants.

Significance

Spring showers

As mold spreads, it generates white, and purple-ish-gray patches in the lawn. These are generally more noticeable in the morning. Later in their life progression they cause gray or black crusty powder balls to collect on the grass looking like cigarette-ash on the blades.

Geography

Managing mold.

Molds occur mostly during the spring in warm, wet conditions and may crop up in the same location each year. During episodes of extended rainfall and high humidity slime molds can form on and then thrive in your more shaded grassy areas, potted plants and low hanging vegetation. Because slime mold grows only over the surface, it generally causes no damage to the grass itself. However, if left on grass for a long time it may eventually do harm. If the area is consistently in the shade, the lack of light may weaken the grass, cause it to yellow and become more vulnerable to other molds and diseases.

Prevention/Solution

Use your broom.

Sweep slime mold off with a broom. If it's real stubborn, use a rake. Other than the plethora of chemical treatments found at your local gardening store, often baking soda spray, potassium bicarbonate will eradicate it--so will sprinkling cornmeal. To avoid mold in your more shaded areas, water in the morning and allow lawn to dry over the course of the day. Water less often, and for a longer time instead of watering daily. If the mold continues to appear you can also make a mixture of vinegar as a fungal treatment and spray it on top of the soil a few times before you water.

Benefits

There is a benefit of molds: they facilitate the break down of branches, fallen leaves and other types of dead plants that you add to your compost pile.

References

• USDA: Soil Management
• Dirt Doctor: Organic Remedies for Mold
• UBC Botanical Gardens

Resources

• Clemson University Extension: Plant Problems