Coreopsis tripteris

August in my garden consists of a lot of yellow, and a lot of tall plants. Coreopsis tripteris (tall tickseed) is one of the newer additions to my yard and is no exception to this. It doesn’t reach the lofty heights of Agastache nepetoides (yellow giant hyssop) or Silphium perfoliatum (cup plant), but it easily tops 6’ in only its second year (and this was a very dry year here). Its leaves, too, are much more delicate than some of the other garden giants and thus it provides a very airy elegance in the flower bed. It can be a bit aggressive given adequate moisture, but if you have the room, it is a lovely plant as a backdrop. (Plant Description and In the Garden sections, below, courtesy of Shaun Booth from In Our Nature.)

Common Name: Tall Tickseed

Scientific Name: Coreopsis tripteris

Family: Asteraceae (Aster Family)

Alternate Common Names: Tall Coreopsis

Plant description: Tall Tickseed features slender, smooth, cylindrical stems that are unbranched except for along the upper half of the plant. Opposite leaves are found along the full length of the stems. These leaves are odd-pinnate with 3-5 leaflets, each measuring up to 12.7 cm long and 2 cm wide. Leaflets have smooth margins, a linear-elliptic shape, a pointed tip and a wedge-shaped base. Lateral leaflets have no leaf stalk while the end leaflets do have a leaf stalk. Leaflets are further characterized by smooth upper leaf surfaces and finely hairy undersides. The uppermost stems are topped with solitary flowers that collectively form open, loosely flat-topped flower clusters. Each flower is borne on a flower stalk that is up to 25cm long. These flower stalks may have a couple leafy bracts along them. Individual flowers measure up to 5cm across and feature 8 widely spreading ray florets (petals) surrounding a dense cluster of brown disk florets. Flowers give way to small (4-5mm), oblong, brown seeds with winged sides.

In the Garden: Tall tickseed is a stately plant with radiant yellow flowers that reach for the sky. It is valued as a dependable structural plant with noteworthy winter interest.

Skill level: beginner

Lifespan: perennial

Exposure: part shade to full sun

Soil Type: well drained

Moisture: moist to mesic (to dry) – will tolerate some drought

Height: 60-240 cm

Spread: 60-240 cm

Bloom Period: Jul, Aug, Sep, Oct

Colour: yellow

Fragrant (Y/N): N

Showy Fruit (Y/N): N

Cut Flower (Y/N): Y

Pests: no significant pests

Natural Habitat: dry to wet prairies and meadows, marshes, oak forests (especially borders and clearings), fields, roadsides and railroad rights of way

Wildlife value: flowers are visited by frequented by butterflies, skippers and native bees, and birds are known to feed on the seeds

Butterfly Larva Host Plant For: Southern Dogface butterfly (Zerene cesonia) – though this species rarely visits Ontario

USDA Hardiness Zone: 3-9

Propagation: [C(60), L; D] Easily propagated by surface sown seeds (requires light for germination) in late fall. The seeds will germinate in a week or two and overwinter as a small cluster of leaves. If planting in the spring, the germination will benefit from 60 days of cold moist stratification before direct sowing. This coreopsis is also readily propagated by dividing the root clump in early spring or after it has finished flowering in the fall.

Additional Info: If grown in light shade, tall coreopsis tends to be open and leggy with a tendency to lean toward the sun. Grown in full sun, plants tend to be sturdier and have many more blooms. As with other coreopsis, deadheading will extend the bloom period and prevent unwanted seedlings, especially in smaller gardens where this plant can be aggressive especially if there is adequate moisture.

Native range: