by Carolyn Singer, Foothill Cottage Gardens
Fine Gardening, July/August 1993
When late frosts in May remind me that summer has not yet arrived in my Sierra Nevada foothill garden, the first golden flowers of coreopsis have already emerged—a gentle prelude to the symphony of color that will fill my flower borders until late fall.
Coreopsis, commonly called tickseed, are compact, long-flowering plants. Their drifts of daisy-like flowers light up the garden with bright splashes of gold, rust and even pink.
I first discovered Coreopsis, which are tough North American natives, when I sowed a wildflower mix in my garden a decade ago. Only the Coreopsis survived to bloom again in my rocky, clay soil and dry climate. Since then, I've owned my own nursery for 12 years, and in the nursery and in my garden, the many kinds of Coreopsis have amply rewarded me with a wide range of delicate foliage, flower forms and colors.
Coreopsis are companionable plants that combine well with many perennials. The earliest-blooming Coreopsis provide a rich touch of gold that is particularly lovely next to perennial alyssums. Later in the season, Coreopsis flowers combine beautifully with the rust-reds and oranges of rudbeckias and blanket flower, and the scarlet, orange or soft yellow flowers of Geum quellyon. A Coreopsis with pale yellow flowers seems to glow against flowers with deeper hues, while the delicate, rosy pink flowers of a species coreopsis are lovely next to the bright blooms of the purple coneflower.
The delicate, thread-like foliage of some Coreopsis is beautiful in contrast to the bolder green leaves of many perennials, and it's especially lovely against the variegated leaves of Chrysanthemum pacificum and the silver leaves of lamb's-ears and artemisias.
The annual and perennial species of Coreopsis are as easy to grow as they are durable. Most thrive in dry soils. A few prefer moist growing conditions, expanding the landscape uses for these flowers. After a dozen years of experimenting with various Coreopsis species and cultivars, I have chosen seven that I will happily share with you.
Favorite coreopsis
An annual coreopsis—Sometimes called dyer's coreopsis, Coreopsis tinctoria is named for the rusty red and bronze dyes that can be made from its flowers. The petals are predominantly golden yellow and contrast strikingly with wine-red centers. Slender stems and delicate foliage enhance this rugged annual, a Southwestern native that tolerates poor soil (and even smog). It makes a handsome display in both sunny and semi-shady gardens. I sow seed of C. tinctoria in drifts outdoors in spring, allowing the long-stemmed, 18-inch to 4-foot tall plants to grow as close together as 6 inches for support. Plants will sow seeds for new generations if you wait until late summer to cut them back. Seeds are available for both tall forms and dwarf forms.
Big flowers—Perennial coreopsis provide season-long color in rock gardens, perennial borders and naturalized, drought-prone areas. Two of my favorites are C. grandiflora, which means large-flowered coreopsis, and C. lanceolata, or lance-leaved coreopsis. Both of them are hardy to USDA Hardiness Zone 4 (-30 degrees F).
I love the species C. grandiflora for its bright yellow, daisy-like flowers with yellow centers. It has a sprawling habit and flower stalks that reach 3 feet in height, so I give it lots of room to spread, or I place it next to plants that have strong stems to hold it up. C. grandiflora is lovely next to the pale orange and yellow flowers of Peruvian lily (Alstroemeria) and the airy, white flowers of feverfew (Chrysanthemum parthenium). Removing faded flowers will keep the plant blooming into August. By then, I am usually frustrated with its sprawling habit and cut it to the ground. The foliage quickly regrows, adding a handsome, neat green plant to my late summer and fall border. C. grandiflora is easily grown from seed.
‘Sunray’, a cultivar of C. grandiflora, is so special that it won the European Fleuroselect Award (in 1980), the first perennial ever to take this honor. ‘Sunray’ literally bursts into bloom in late spring and early summer, when the compact plant covers itself with double, golden, 2-inch diameter flowers. The 24-inch tall plants have long stems suitable for cutting. Happiest in full sun or half-day sun, ‘Sunray’ and the similar-looking, double-flowered cultivar ‘Early Sunrise’ bloom all summer with frequent deadheading and adequate moisture. They are easily grown from seed, sometimes even blooming the first season.
Long bloom—There are few perennials that will endure morning shade followed by afternoon sun and temperatures above 90degrees F, but C. lanceolata is one that will. Light shade or full sun suits it best. It blooms as early as March in warm areas of California, but in my garden the show begins in late April or early May and lasts until November. ‘Baby Sun’, ‘Baby Gold’, ‘Goldfink’ and ‘Brown Eyes’ are compact cultivars of C. lanceolata, ranging from 10 inches to 16 inches in height. All have golden yellow, single flowers. ‘Brown Eyes’ has rust-red markings at the base of each petal. C. lanceolata and its cultivars are excellent in the rock garden, in containers and as edgings. Their bright green foliage is attractive. and their short stems produce flowers that can be cut and then used in small bouquets.
Quick spread—Threadleaf coreopsis (C. verticillata) is hardy to Zone 3 (-40 degrees F). A native of the south. it spreads quickly in enriched soil, establishing strong plants that look good in the perennial border or rock garden. (Verticillata means whorled leaves.)
My favorite cultivar is ‘Golden Showers’, which has outstanding foliage before and after it blooms Delicate, l-inch, golden flowers on slender but sturdy, 2-foot stalks cover the foliage for several weeks from mid- to late summer. Plants placed 18 inches apart will quickly fill in to create a drift of gold. ‘Golden Showers’ is a strong grower, but it's not invasive in my garden, and it performs beautifully in full sun or morning-to-mid-day sun. Propagate it by division or seed.
Another good cultivar of threadleaf coreopsis, ‘Zagreb’, grows to 2 feet in height, but spreads little from year to year in my garden—my oldest plan is only 19 inches wide after six years. The foliage and flowers of ‘Zagreb’ resemble those of ‘Golden Showers’. Its growth habit is delicate and compact, and the plants tend to have a mounding shape. I've paired it with the robust leave and orange-gold flowers of the perennial Rudbeckia fulgida ‘Goldsturm’.
I find the most uses for C. verticillata ‘Moonbeam’, a cultivar that has tiny leaves, a spreading habit an delicate, pale yellow flowers from mid summer through fall. In the rock garden its 6-inch to 12-inch wide mounding shape looks refined, leaving accent rocks exposed. Tumbling lightly over a garden wall, ‘Moonbeam' is striking against the creeping, pink-flowered perennial soapwort (Saponaria ocymoides). In the perennial border, its pale yellow blossoms form pleasing combinations with flowers and foliage in cool shades—blue, pink, purple and gray---or with warm golds, reds and oranges. Of all the coreopsis, ‘Moonbeam’ is the most drought-tolerant. I propagate it by both division and cuttings.
Pink flowers—The unique beauty of C. rosea, which is hardy to Zone 3(-40 degrees F), lies in its color. The only pink coreopsis. it has light rosy-pink flowers with yellow centers that appear from mid- to late summer. The 2-foot tall foliage, which is a delicate, dark green, makes it valuable for edging. C. rosea prefers moist soil; it even tolerates being planted at water's edge. It spreads easily in good garden soil and can be divided
For part sun—A native of the midwest and southeast, eared coreopsis (C. auriculata), which is hardy to Zone 5 (-20 degrees F), prefers morning sun. This Coreopsis produces single, wide, golden yellow flowers over a long season beginning in late April in cooler regions. But where summers are hot, it does not perform as well as other species. The 12-inch tall plants spread easily by stolons in moist soil. The dwarf C. auriculata 'Nana', at 6 inches to 12 inches in height, makes an excellent perennial addition to the rock garden.
Promoting healthy plants
Pests seldom bother coreopsis, with the exception of browsing deer, which only occasionally nibble the flowers. Deer seem particularly fond of C. rosea, but they don't eat enough of mine to spoil its lovely display of pink flowers.
Healthy plants are rarely affected by disease. Mildew may be a problem on the larger-leaved coreopsis, but it doesn't usually appear until after the first flowering. I cut back affected foliage even if it means cutting back the entire plant. The renewed growth is strong. If cut back by mid-summer, a coreopsis will produce a second bloom.
Good soil will promote healthy plants and discourage pests. I mix compost generously into my clay soil. Here in the Sierra foothills I must also add organic phosphorus and oyster shell to the acid soil to bring the pH closer to the range of 6.5 to 7.5 that Coreopsis prefer. I apply a 2-inch thick mulch of compost and leaves to conserve moisture in the soil on hot summer days.
| Coreopsis are easy to propagate from seeds, cuttings or divisions.
The seeds need light in order to germinate, so broadcast them
over finely-raked soil when the ground warms in spring. Seeds
of most coreopsis need moist soil to germinate, but young plants
quickly adapt to dry conditions. However, seeds of named cultivars
may produce offspring that don't resemble the parent plants. Propagating
these cultivars by cuttings or divisions will ensure identical
offspring. You can root tip cuttings of C. verticillata anytime during the growing season, but divisions are best made
in fall or early spring when the plants are dormant. You can divide
clumps of Coreopsis in a couple of ways. Dig up clumps of coreopsis
and pry apart the rooted divisions, discarding the old center
crowns. You can also divide clumps in the ground, without disturbing
their roots, by gently digging into the outer edges of the clump,
separating and lifting rooted plantlets.
I enjoy Coreopsis over a long season. Early in the season, I appreciate their delicate foliage and brilliant flowers. But at season's end I especially love watching goldfinches eating coreopsis seeds. This year I intend to plant ‘Early Sunrise’ on the east-facing side of my gold-orange-red border. There, its ruffled, golden flowers will catch the first light of morning, welcoming each day and providing me with another season of Coreopsis-watching. |
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