Compass Plant
Silphium laciniatum
“What a thousand acres of Silphiums looked like when they tickled the bellies of the buffalo is a question never again to be answered, and perhaps not even asked."
— Aldo Leopold, A Sand County Almanac
Rooted for Generations
Compass plant is one of the signature broadleaf plants of the tallgrass prairie, a landscape that once covered much of Iowa and the Midwest. Its height, deeply cut leaves, bright yellow blooms, and deep roots made it conspicuous to Indigenous communities, settlers, naturalists, and prairie travelers.
Today, compass plant can serve as both a garden focal point and a reminder of the depth and complexity of prairie ecosystems. Its long lifespan, deep root system, floral resources for insects, seeds for wildlife, and structural value in grassland habitat make it an especially fitting choice for prairie reconstructions, sunny native gardens, and larger restoration plantings.
Compass Plant At a Glance
Plant Description
Compass plant is a tall, long-lived native perennial in the aster family, typically growing 5–9 feet tall. It has large, rough, deeply lobed basal leaves that can reach 12–24 inches long, along with stout, hairy flowering stems. In mid- to late summer, it produces several large yellow, sunflower-like flower heads near the top of each stem.
Each flower head has narrow yellow ray florets surrounding a center of smaller yellow disk florets. After flowering, the plant forms flattened seeds that provide food for wildlife into fall.
Compass plant gets its common name from its large lower leaves, which often orient along a rough north–south axis. This leaf position may help reduce exposure to intense midday sun, but it is not a precise or dependable navigational tool, despite its name.
Habitat and Range
Compass plant is native to Iowa and is associated with open, sunny prairie habitats. It can be found in upland, dry-mesic, and mesic prairies, as well as prairie remnants, roadsides, railroad corridors, and other open sites with deep soils.
Prairies vary with their position and soil moisture. Upland prairies grow
on higher ground; dry-mesic prairies are somewhat dry, while mesic prairies
have moderate moisture and well-drained soil.
In a home landscape, compass plant is most at home in a sunny native planting, prairie garden, or larger restoration area. It does best where it has abundant sunlight, well-drained soil, and enough space to develop its long taproot. Because mature plants become tall and broad, they are generally best placed toward the back or middle of a planting rather than along a narrow path or directly in front of shorter species.
Wildlife Value
Compass plant is more than a dramatic prairie flower. Its blooms provide nectar and pollen for native bees, including bumble bees, mining bees, and leafcutter bees, while butterflies and hoverflies also visit the flowers. Its seeds feed birds and small mammals, and its tall stems can give prairie songbirds, including eastern kingbirds, a place to perch while hunting insects.
Compass plant also supports specialized prairie insects that use its stems, flower heads, and underground tissues during different stages of their life cycles. Leave stalks standing through winter when possible to preserve food, cover, and shelter for wildlife and overwintering insects.
"They came up promptly, but after five years of waiting, the seedlings are still juvenile
and have not yet borne a flower stalk. Perhaps it takes a decade for a Silphium
to reach flowering age; how old, then, was my pet plant in the cemetery? It may have been older than the oldest tombstone, which is dated 1850. Perhaps it watched the fugitive
Black Hawk retreat from the Madison lakes to the Wisconsin River; it stood on the route
of that famous march. Certainly it saw the successive funerals of the local pioneers
as they retired, one by one, to their repose beneath the bluestem."
— Aldo Leopold, A Sand County Almanac
Planting Seeds
Compass plant seeds benefit from a cold, moist period called stratification before spring sowing. This winter-like treatment helps break dormancy and improve germination. Each method can help prepare compass plant seeds for germination:
🍂 Fall Planting
After the first hard frost, sow seeds outdoors in a prepared, weed-free site. Press the seeds firmly against the soil and cover them very lightly with soil or sand. Winter weather will provide the cold, moist conditions the seeds need. Water gently if the soil is dry.
❄️ Winter Sowing
Sow seeds in outdoor containers with drainage holes, or scatter them over a prepared planting area. Keep the seeds in contact with the soil and cover them only lightly. Winter’s changing temperatures and moisture will help prepare the seeds to germinate in spring.
🌤️ Spring Planting
Mix seeds with a barely moist medium, such as damp vermiculite, sand, or a paper towel, and seal them in a labeled container or bag. Refrigerate for about 60 days. Check periodically to ensure the medium remains moist but not soggy or moldy. Before sowing, you may carefully nick the seed coat with a sharp knife, though this step is optional. Sow seeds in a prepared site, press them into the soil, cover lightly, and water gently.
First-year seedlings may remain small as young plants devote much of their energy to developing deep roots. Flowering may begin in two to three years, though plants in prairie settings or less-than-ideal conditions can take longer—sometimes four or five growing seasons—to bloom.
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"Why does Silphium disappear from grazed areas? I once saw a farmer turn his cows into a virgin prairie meadow previously used only sporadically for mowing wild hay. The cows cropped the Silphium to the ground before any other plant was visibly eaten at all. One can imagine that the buffalo once had the same preference for Silphium, but he brooked no fences to confine his nibblings all summer long to one meadow. In short, the buffalo’s pasturing was discontinuous, and therefore tolerable to Silphium."
— Aldo Leopold, A Sand County Almanac
Care Tips
☀️ Light
Compass plant needs full sun. Choose a site with at least six hours of direct sunlight each day; more sun is generally better. Plants grown in too much shade may stretch, lean, or produce fewer flowers.
🪨 Soil
Compass plant tolerates a range of well-drained soils, including loams and prairie soils. It performs best in deep soil with access to moisture below the surface. Once established, it can grow in dry to medium conditions, but it is not well suited to shallow, compacted sites where its long taproot cannot develop.
💧 Water
Water regularly during the first growing season so seedlings and new transplants can establish strong roots. Once established, compass plant is drought tolerant because of its extensive taproot. Avoid prolonged soggy conditions, especially in compacted soil.
🌱 Fertilizer
Compass plant is adapted to prairie conditions, so fertilizer is generally unnecessary. Mature plants can become large and top-heavy, especially in rich garden conditions, so avoid over-enriching the planting area.
✂️ Pruning
Do not cut back compass plant during the growing season unless a stem has broken or needs support. Staking may be helpful in some garden settings.
After flowering, leave the stems and seed heads standing through fall and winter whenever possible. The seeds provide food for wildlife, while the standing stems add structure to the winter garden and may shelter native insects. Cut the stems back in early spring, before new growth emerges. If space allows, place the cut stems in a brush pile or natural area rather than removing them immediately, giving any insects sheltering inside more time to emerge.
🌾 Placement and Companions
Plant compass plant where it can remain for many years. Its deep taproot makes established plants difficult to transplant or divide, and mature plants need plenty of room. Place it among sturdy, sun-loving prairie species rather than beside low-growing plants that its large basal leaves may shade.
For a natural prairie planting with flowers across the growing season, consider pairing it with prairie dropseed, big bluestem, Indiangrass, prairie blazing star, purple coneflower, wild bergamot, cup plant, rattlesnake master, and prairie dock.
"Silphium first became a personality to me when I tried to dig one up to move to my farm.
It was like digging an oak sapling. After half an hour of hot, grimy labor,
the root was still enlarging, like a great vertical sweet potato. As far as I know,
that Silphium root went clear through to bedrock."
— Aldo Leopold, A Sand County Almanac
Plant Sources
