Compass Plant, Silphium laciniatum L., Native Minnesota Wildflower plant, Eloise Butler Wildflower Garden

	Plants of the Eloise Butler Wildflower Garden
	Common Name	Scientific Name	Plant Family	Garden Location	Prime Season
	Compass Plant	Silphium laciniatum L.	Aster (Composite)	Upland	Late Summer to early Autumn
Other names and notes	A tall plant of the Upland Garden, reaching 6 - 8 feet. Stems and the deeply lobed alternate leaves are rough with hair. The ray flowers are yellow, 2 1/2 to 4" wide with usually 17 - 25 rays. the central disk can be 3/4 to 1 1/4" wide. Flowers appear in several heads in long branched clusters. The common name comes from the tendency of lower leaves to be somewhat upright with the edges aligned in a north-south direction. These leaves are very deeply pinnately-divided. It is sometimes listed in references as Rosinweed, but that is a different species. S. laciniatum is one of four Silphiums in the Garden.


Blooms of late July.

Notes: This plant was listed on Martha Crone's 1951 inventory of plants in the Garden at that time. The plant is native to Minnesota in the SE quarter from Ramsey county south and also across the southern tier of counties to the Dakota border. For more detail on this plant and the other Silphiums, see the article "The Four Silphiums".

Eloise Butler wrote of this plant: "The interesting Rosin, or Compass Plant of the prairie (Silphium laciniatum L.) is of the same genus as the cup plant. Its leaves are cut edgewise and point due north and south. Persons lost on a trackless, uninhabited prairie might find their bearings by this vegetable compass. An army officer stationed on the western plains, the first observer of the plant, thought the leaves must have the properties of the magnetic needle. Failing to prove this theory by experiments, he forwarded specimens of the Silphium to Dr. Asa Gray, the American Darwin, who suggested that the peculiar position of the leaves was for the purpose of avoiding the direct rays of the sun in order to check too great a loss of water by transpiration. Since that time “polarity” has been observed in the leaves of many other plants growing in drought regions or in exposed situations, as the eucalyptus trees of Australia. Such trees, of course, afford no shade. The habit may be noted in the roadside weed prickly lettuce, and in some degree even in the garden lettuce." Published in the Minneapolis Sunday Tribune, July, 16, 1911.

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References: Plant characteristics are generally from sources 15, 16, 30, 31, 33, W2 & W3. Distribution principally from W2 and also 31, 34 and W1. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.

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