Spanish Moss, Lichens & Slime Molds

Revised and images added by Joey Williamson, HGIC Horticulture Extension Agent, Clemson University, 11/13. Originally prepared by Nancy Doubrava, HGIC Information Specialist, and Bob Polomski, Extension Consumer Horticulturist, Clemson University. New 05/99. Images added 05/08.

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Spanish Moss

Spanish moss (Tillandsia usneoides) is one of the most misunderstood plants found throughout the Deep South. To native South Carolinians, these gray strands draping from the branches of live oaks and other trees are a natural part of the scenery, while many newcomers fear that it may be killing their trees.

Spanish moss on live oak
Spanish moss on live oak
Karen Russ, ©2008 HGIC, Clemson Extension

Contrary to popular belief, Spanish moss causes little to no detrimental effect on a host tree. It may appear to have roots growing within the host tree, but it is an epiphyte. Epiphytes grow on other plants without taking any water or nutrients from them, and use the host plant for support and protection.

Spanish moss can be seen hanging from many different types of hosts, including pecans, oaks, pines, and even telephone lines. Spanish moss is most evident in trees that are declining due to some other reason. Heavy infestations can lead to further decline by shading out the lower leaves of the tree. It is far too often that homeowners waste a lot of time and energy trying to remove it from their trees, since it is actually causing no harm.

Treatment: Spanish moss is too often blamed for problems that are caused by other reasons. Increasing tree vigor by proper watering and fertilization is one way to restrict the growth of Spanish moss. There are no chemical treatments available for its control. This small native plant should be appreciated as a part of South Carolina 's natural heritage and not blamed as the cause of other plants' problems.

Lichens

A lichen is an unusual plant composed of a fungus and an alga living together in the same body. Lichens often appear as green to gray-green leafy or crusty growths on the trunks or branches of plants. They are not harmful to the plant, and are merely using the plant as a place to anchor.

Two types of lichens growing on a branch
Two types of lichens growing on a branch.
Karen Russ, ©2008 HGIC, Clemson Extension

Typically, they occur in abundance on plants that are declining in health or vigor. They are in no way responsible for the poor health of the plant. Less vigorous plants tend to be more open, increasing sunlight penetration and subsequent lichen growth.

Treatment: Controls are not necessary, since lichens are not harming the plant. Lichens will gradually disappear if plant health is restored. Remember they will probably reappear if you do not correct the true cause of the plant's decline.

Slime Molds

Slime molds are fungus-like organisms (Myxomycetes) and live in cool, shady damp places such as the soil surface of lawns, on organic mulches, or on rotting logs. Slime molds feed on decaying organic matter, bacteria and fungi in the soil. They do not feed on green plants. Because slime molds grow on dead organic matter, they do not pose a direct threat to any plants in the garden.

Slime molds come in a variety of colors, including brown, salmon, off-white, yellow, orange or brick red. Some appear in the spring and look like white-yellow globs of plaster on mulch in landscape beds, such as the dog vomit slime mold (Fuligo septica). These occur mostly during the spring during warm, wet conditions and may appear in the same location each year.

Dog vomit slime mold fuligo septica on hardwood
“Dog vomit” slime mold (Fuligo septica) on hardwood mulch.
© Thomas F. Lytle

In lawns, slime molds produce white, gray or purple patches in the lawn that are usually visible in the morning. They are especially noticeable later in their life cycle when they form grayish or black crust-like powdery balls on blades of grass.

Although they may look alarming, slime molds generally pose no harm to lawn grasses. However, prolonged and excessive shading may cause a temporary yellowing of turfgrass blades. A very heavy covering of slime mold may temporarily make an undesirable appearance in the lawn.

Gray slime mold (Physarum cinereum) on white clover and grass in lawn.
Gray slime mold (Physarum cinereum) on white clover and grass in lawn.
Joey Williamson, ©2012 HGIC, Clemson Extension

Treatment: Control of slime molds is not necessary, since they do not pose a threat to any plants in the garden. The slime molds will disappear in dry weather. The fungal mass can be removed by spraying the turfgrass leaves with a strong stream of water or by mowing when weather conditions are dry. In wet or humid weather, remove slime mold with a rake or broom, since spraying with water will spread the mold to other areas. In hardwood bark mulch, the slime mold along with the colonized mulch can be removed by pitchfork. If left alone, the slime molds will turn black and disintegrate within a few days.

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