Cotula is a plant genus that is part of the Asteraceae family. It contains about 55 species of annual and perennial plants, most of which are native to Australia and Africa. The plants feature button-shaped flowers and silvery foliage. Generally, plants of this category are grown between paving stones or in rock gardens. Most are susceptible to fungal diseases such as root rot.
The name of this genus is derived from the Greek word kotile, which translates to "small cup." It is believed to describe the shape of the flower. The common name for these plants is bachelor's button, which also describes the shape of the flower, or carrot weed, which describes the carrot-like leaves. Several species have variations of the common name. For example, Cotula australis is called the southern waterbutton, and Cotula coronopifolia is known as brass button.
Cotula species are located throughout the world. C. coronopifolia and C. turbinata are native to South Africa, while C. australis populates Australia and New Zealand. C. mexicana is grown in California and Mexico.
C. hispida, also called silver cotula, generally grows 4 inches (10 cm) in height and spreads 12 inches (30 cm). This mat-forming plant is an evergreen perennial that features soft, silky leaves. The silvery-gray foliage provides a nice contrast when planted with other perennials. Each stem is leafless and has one button-shaped, yellow flower atop it. The flower isn't fragrant nor does it attract butterflies.
In order for silver cotula to grow well, it is recommended to grow the plant in well-draining, fertile soil. This plant is adaptable to different soil conditions. It can tolerate loamy or sandy soil with a pH that is either acidic or alkaline. It can't thrive in wet conditions during the winter, so a layer of mulch is typically added to the soil to reduce soggy soil conditions. An area that is exposed to direct sunlight throughout the day is ideal for this plant.
A common problem with silver cotula is root rot. Root rot is a fungal disease in which fungal spores attack the roots of the plant. The leaves of the plant usually exhibit the first signs of disease. They generally appear faded or wilted and eventually drop. Root rot essentially deprives the plant of nutrients; the roots are damaged to the point where they can no longer absorb nutrients from the soil.