Compass plant

Sun

Full sun; shade encourages leaning and fewer flowers.

Water

Water regularly during establishment. Established plants tolerate drought, though prolonged dry weather can shorten flowering.

Soil

Deep, well-drained soil, including loam, clay loam and sandy loam; tolerates relatively poor soil but not persistent waterlogging.

Height

5-9 ft (1.5-2.7 m)

Spread

2-3 ft (0.6-0.9 m)

Flowers

Yellow sunflower-like flowers from midsummer into early autumn.

Foliage

Large, rough, deeply lobed green leaves, mostly near the base, with smaller leaves up the flowering stems; dies back in winter.

Growth

Slow to establish, then moderate; develops a substantial taproot before producing its full flowering height.

Care needed

Low

• Pollinators
• Drought tolerant
• Cold hardy
• Heat tolerant
• Wildlife
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   2.5 ft (0.76 m)

3. After 2 years

   4 ft (1.2 m)

4. After 3 years

   6 ft (1.7 m)

5. After 5 years

   7 ft (2.1 m)

   full size

About 4 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

the US and Canada

Growth rate

Slow

• Choose a permanent position with deep soil; established taproots are difficult to move.
• Water deeply during the first growing season, letting the surface soil dry between waterings.
• Avoid routine feeding and rich manure, which can encourage weak, leaning stems.
• Apply a light organic mulch around young plants, keeping it clear of the crown.
• Support stems early if the site is exposed or the soil is unusually fertile; plants in full sun usually stand without staking.

Pruning. Leave stems and seedheads standing through winter for birds and structure. In late winter or early spring, cut old stems to about 4-6 in (10-15 cm) above ground before new growth develops.

Autumn

Sow fresh seed outdoors in a prepared seedbed or deep pots for natural winter chilling.

Late winter

Cut back old stems before new basal leaves emerge.

Spring

Plant young plants in their permanent positions and water them in thoroughly.

Late spring

Weed around young rosettes and add discreet supports where needed.

Summer

Water first-year plants during dry spells; check crowded foliage for mildew.

Early autumn

Collect ripe seed if wanted, leaving some seedheads for birds.

• Place at the back of a sunny border for tall yellow flowers above lower perennials.
• Combine with big bluestem and prairie dropseed in a prairie-style planting.
• Plant in loose groups with coneflowers and blazing stars for a long-season pollinator border.
• Retain winter stems as vertical accents in a large naturalistic garden.

Garden styles it suits: Midwest prairie, Native meadow, New perennial (prairie), Wildlife garden, Pollinator garden and Winter interest.

Plant it with: Big bluestem, Prairie dropseed, Purple coneflower, Rattlesnake master, Prairie blazing star and Wild bergamot.

Wildlife: Flowers attract native bees and other pollinating insects. Seedheads provide food for seed-eating birds, including goldfinches in its native range, and standing stems offer overwintering habitat for insects.

• Leaning or floppy stems: provide full sun, avoid high-nitrogen feeding and support stems early if necessary.
• Powdery mildew: allow good spacing and airflow; avoid crowding and water the soil rather than the foliage.
• Rust or fungal leaf spots: remove badly affected leaves and clear infected fallen foliage; minor damage rarely needs treatment.
• Crown or root rot in wet ground: improve drainage or choose a better-drained planting site; avoid winter-saturated soil.

Not known to be toxic to people, cats, dogs or horses. Species-specific safety information is limited, so do not treat any part as edible or encourage pets to chew it.

• Prairie dock (Silphium terebinthinaceum)

  Has very large, mostly unlobed basal leaves and comparatively bare flowering stems; compass plant has deeply cut leaves.

• Cup plant (Silphium perfoliatum)

  Has broad, opposite leaves joined around the stem to form water-holding cups; compass plant lacks these cups and has deeply lobed leaves.

• Rosinweed (Silphium integrifolium)

  Has mostly opposite, unlobed leaves along the stems and is generally shorter; compass plant has large, deeply divided basal leaves.

The common name refers to the tendency of its basal leaf blades to align north–south, with their broad surfaces facing east and west, while laciniatum means deeply cut.

Propagation. Grow from seed sown outdoors in autumn, or give seed about 60 days of moist chilling before spring sowing. Use deep pots and plant seedlings out while young; division and transplanting established plants are difficult because of the taproot.

Accepted botanical name

Silphium laciniatum

In the US and Canada

Native in Canada and the lower 48 states.

Native range

Alabama, Arkansas, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Michigan, Minnesota, Mississippi and Missouri.

Measured

Average height 161 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.