Silphium laciniatum (compass plant) flowers are reminiscent of yellow sunflowers and are borne on flowering stalks up to 10 feet in height. It can be one of the most prominent plants in the garden.
This Asteraceae is native to North America from Ontario through eastern and central United States and as far west as New Mexico. Plants are known to be long-lived, partly due to their long, deep tap root that can be up to 3 inches in diameter and grow to 20 feet deep.
Silphium laciniatum “pushes” its flowers high because, as a foundation plant of tallgrass prairies, the plant needs to present its flowers to pollinators at a height well above the surrounding tall grasses that dominate these natural areas.
In gardens, we are able to take advantage of this evolutionary adaptation to create a strong vertical structure that adds the feeling of height to a planting area.
In addition to the tall flowering stalks, the leaves of compass plant are quite interesting. The deeply cut, rigid, sandpaper-textured leaves are held vertically toward the base of the plant and will orient their blades in an east-west orientation–hence the common name compass plant.
This phototropic response is one mechanism used by S. laciniatum to minimize exposure to solar radiation as a means to control water loss (i.e., transpiration). Compass plant is a great plant choice for attracting pollinators and for providing a winter food source for birds.
|Botanical Name||Silphium laciniatum|
|Common Name||compass plant|
|USDA Zone||3 thru 8|
|Light Requirement||Full Sun|
|Season(s) of interest||summer, fall, winter|
|Height and Spread||5-9ft x 1-3ft (1.5-2.7m x 0.3-0.9m)|
|Attracts Wildlife||Provides Food for Birds, Attracts Pollinators, Rarely Browsed by Mammalian Herbivores|
|Additional Information||Native to Chicago Region. Native range: Quebec, west to Montana, south to Arizona, east to Louisiana and Florida.|
|Location in Lurie Garden||West Meadow, East Meadow|