Compass Plant

CHARACTERISTICS
Plant Height 6 to 12 ft.
Botanical Name Silphium laciniatum
Life Cycle Perennial
Environment Full Sun
Preferred Sites Upland/Grassland - Disturbed
Bloom Period July-September
Flower Color Yellow
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Description

A mature specimen of this native perennial plant is charactarized by a central stem that is thick, light to medium green, and has conspicuous white hairs. There is some branching into flowering stems in the upper part of the plant. The basal leaves are 12-24" long and about half as wide. They are covered in fine white hairs, broadly lanceolate in overall shape, but deeply lobed or pinnatifid. The leaves become much smaller as they ascend up the stem. The inflorescence is very tall and elongated, with yellow composite flowers about 3-4" across. They resemble wild sunflowers in overall size, shape, and structure. However, like other Silphium spp., the small tubular disk florets are sterile, while the ray florets are fertile. There is little floral scent. A mature Compass Plant has 6-24 of these composite flowers that bloom during mid-summer for about 1½ months. The seeds are large-sized, but flat and light, and can be carried several feet by the wind. A large central taproot can extend 15 ft. into the ground. A resinous substance is produced by the upper stem when the plant is blooming. This plant can live up to 100 years.

CULTIVATION: The preference is full sun and moist to slightly dry conditions. A deep loamy soil is preferred for the central taproot. It takes several years for a seedling to develop into a full-sized mature plant. Mature plants are easy to maintain, resist drought, and can handle competition from other plants. If planted on a slope, there is a tendency to flop over, particularly while blooming.

RANGE & HABITAT: This is a typical plant of black soil prairies in the tallgrass region. It often co-occurs with Andropogon gerardii (Big Bluestem). Other habitats include sand prairies, savannas, glades, and areas along railroads. Compass Plant is fairly common throughout most of Illinois, except in the SE and scattered Western counties, where it is uncommon or absent. This plant recovers from occasional fires readily. The common name is derived from the belief by pioneers that the leaves of Compass Plant pointed in a North-South direction. While this is probably true more often than not, it is not always reliable. The resin was used by Indian children as a chewing gum. With its imposing heighth, interesting leaves, and abundant yellow flowers, Compass Plant is an extraordinary plant. No tallgrass prairie is complete without a sizeable population of them.

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