Callirhoe is a flowering plant in the Malvaceae family, commonly known as the mallow or poppy mallow. It's species is a small group of plants native to the prairies of North America. Most varieties of Callirhoe are herbaceous perennial plants with cup shaped flowers that demonstrate nastic movement. Callirhoe plants have a tap root, which makes them well adapted to dry weather conditions.
Callirhoe is a mat-forming plant. It grows approximately 12 inches (about 30 cm) tall and spread to two or three feet (about 60-70 cm). Callirhoes are grown easily from seed, but are difficult to transplant. Callirhoe is an herbaceous plant — i.e., a plant with growth that dies back to the ground each year — with a soft, green stem. As such, it rarely survives temperatures below 38 degrees Fahrenheit (about 3.33 degrees Celsius).
The leaves of the Callirhoe are generally a gray green color, and the stems have what appear to be fine, white hairs. The flowers of the Callirhoe have five petals. The flowers all have a white center and can be pink, purple, or a reddish violet color.
The flowers of the Callirhoe open in the morning in the presence of sunshine and close again at night. This is known as nastic movement, specifically a photonastic response. It is believed that by closing at night, the flowers conserve valuable pollen. These movements occur very slowly and are not evident to the eye. As a result, the response is best viewed through time lapse photography.
Callirhoe has a tap root system. A tap root is a somewhat enlarged, straight and narrow root that grows downward. Carrots, turnips, and radishes are good examples of a plant with a tap root.
In contrast to a fibrous root system, in which thinner roots spread outward, a tap root grows vertically into the soil. In this way, the tap root can draw water from deeper in the soil. This makes the Callirhoe more resistant to drought and, as such, is a good plant for dry areas with unpredictable rainfall.
Mallow grows well in rocky conditions and poor soil. Because it has a tap root, it is difficult to remove once it becomes established in an area. Poppy mallow grows as a wild flower in many parts of the southwestern United States.
Poppy mallow is becoming increasing popular as a garden plant. It grows well on slopes, in rock gardens, and can be trained to cascade over retaining walls. Callirhoe will grow successfully in south or west facing flower beds that heat up during the summer. It can thrive in a wide variety of soil types and requires very little water once established.