compass plant

not listed

NNR - Unranked

SNR - Unranked

not listed

Compass plant is an erect, perennial forb that rises on usually a single stem from a deep, woody taproot that can extend 15′ into the soil. It can be 3′ to 6½′ in height, but is usually no more than 8′ tall. It is a long-lived plant, sometimes surviving up to 100 years.

The stem is erect, stout, light green or medium green, round in cross section, and unbranched below the inflorescence. It is moderately covered with relatively long, white hairs and also with minute, usually gland-tipped hairs.

Basal leaves are egg-shaped in outline, 12″ to 24″ long, and 6″ to 12″ wide. They are rough to the touch, thick, and leathery. They are deeply cut almost to the midrib into 3 to 15 primary lobes (pinnatifid) which are sometimes again lobed (bipinnatifid). The primary and secondary lobes are oblong to oblong triangular. They taper to a sharp point at the tip and are broadly attached at the base. The upper and lower surfaces are sparsely to moderately covered with spreading hairs and are dotted with scattered, stalkless or impressed glands. The margins are untoothed or may have a few teeth. The axis of the leaf is oriented north and south so that the blade faces east or west, thus avoiding the hot midday sun. Basal leaves are present at flowering time.

Stem leaves are alternate, short-stalked or stalkless, and otherwise similar to basal leaves. They become progressively smaller as they ascend the stem. Upper stem leaves 1½″ to 6″ long, short-stalked, and once pinnatifid.

The inflorescence is an elongated, usually branched cluster (panicle) of 6 to 30 flower heads at the end of the stem. The flower heads are short-stalked or nearly stalkless.

The flower heads are 2½″ to 4″ in diameter. The whorl of modified leaves (bracts) at the base of the flower head (involucre) is bell-shaped to hemispheric and ⅜″ to 13 ⁄16″ in diameter. It is composed of 25 to 45 bracts (phyllaries) in 2 or 3 overlapping series. The phyllaries are egg-shaped, sharply pointed at the tip, ¾″ to 19 ⁄16″ long, and often spreading or bent backward at the tip. They are sparsely to densely hairy and are usually also dotted with glands.

There are 27 to 38 ray florets and 100 to 275 disk florets. The ray florets are yellow, ¾″ to 2″ long, and fertile. The disk florets are yellow and infertile.

The fruit is a dry, one-seeded seed capsule (cypsela). The cypsela is black to brown, egg-shaped, flattened, ⅜″ to 11 ⁄16″ long, and ¼″ to ½″ wide. It is broadly winged and has a deep notch at the tip. There is no tuft of hairs attached to the end.

36″ to 80″

Yellow ray florets, yellow disk florets

Dry to moderate moisture. Prairies, railroads, disturbed areas. Full sun.

June to September

Sources

2, 3, 4, 5, 7, 28, 29, 30.

Native

Common

USDA PLANTS recognizes two varieties of Silphium laciniatum. Of these, only the nominate variety, var. laciniatum, occurs in Minnesota. Most other sources do not recognize any varieties.

Plant

Flower Head

Leaves

Leaves in Early Spring

Infructescence