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Coreopsis—The Preferred Name for a Preferred Plant

by Bruce Crawford, Manager of Horticulture, Morris County Park Commission

As we learn plants, the common name is invariably the name we prefer, since it is in a language that makes sense and is easier to recall. Typically, the biggest challenge with common names is the lack of consistency, as they can vary by location and some plants simply have several names. A smaller, yet still problematic challenge is the lack of sales appeal some common names embody. For example, Tickseed is the accepted common name for the genus Coreopsis. Coreopsis is a wonderful genus of garden worthy flowering plants, yet having a common name associated with a dreaded insect can make some individuals question its garden worthiness. Fortunately, there is nothing to fear, since this plant only attracts praise and not ticks!

Coreopsis is a member of the Asteraceae or Sunflower family with 75–80 species stretching from North America south into Mexico and South America. The genus name was crafted by the Swedish botanist Carl Linnaeus (1707–1778) in 1753 from the Greek Koris meaning bug and Opsis meaning like. Yes, even the botanical name references an insect! The botanical and common names stem from the loose resemblance of the seed, technically a dry fruit called an achene to that of an insect or tick.

Zoom in Coreopsis verticillata 'Zagreb'.
Picture 1: Coreopsis verticillata 'Zagreb'.

When I was first starting to learn plants, the most common species available was Coreopsis grandiflora, the Large Flowered Tickseed. The Scottish botanist and florist, Thomas Hogg (1777–1855) is credited with originally naming the plant, perhaps after he immigrated to the United States in 1820. Unfortunately, he failed to adequately describe the plant and it was the English botanist and horticulturist Robert Sweet (1783–1835) who properly described the species in 1826. The challenge I faced with this plant was not the 'buggy' name, but its relatively short lifespan. Growing from 1–2' tall, this species and its cultivars produce such copious displays of 2–2½" diameter flowers and subsequent seed set that the life span is shortened to only a few years. In fact, many species of Coreopsis have a reproductive strategy of perennializing through an abundant production of seedlings while the plants have a short lifespan of 3–5 years.

Zoom in Coreopsis verticillata 'Zagreb' in July.
Picture 2: Coreopsis verticillata 'Zagreb'.

To understand how a plant could have such a seemingly risky strategy, it is best to understand the reproductive nature for the Asteraceae family. When looking at the flower, such as Coreopsis verticillata 'Zagreb' (as seen in Picture 1), what appears as a single flower is actually 50 or so small flowers called florets that are perched on a platform called a capitulum, as seen in Picture 2. What appear to be petals are actually individual flowers called ray florets. These, in turn surround a central boss of golden yellow disc florets. In Picture 1 the outer whirl of disc florets is open. Botanically speaking, all the petals of an individual flower are collectively called the corolla and for the central disc florets the corolla is greatly reduced in size, with the individual petals fused to create a small bristly tube. The corolla of the outer ray florets produces a tongue-like extension that projects outward from the flower head, looking like a conventional petal of a flower and serving to attract pollinators. The pollen receiving stigma is split into two lobes, resembling the letter 'M' as seen more clearly in Picture 2. The dark brown center of the disc florets seen in Picture 1 is actually another tube, in this case created by the fusing of the pollen releasing anthers! The pollen at the tip of the pollen tube ripens first in a floret, before the stigma stretches upwards and splits open, partially explaining why most Coreopsis are not self-fertile. The benefit of this flower structure is its ability to produce an incredible abundance of seed. Unfortunately, production of seed also requires a lot of energy, shortening the lifespan of certain species such as Coreopsis grandiflora to a few years, especially if grown in heavier, moister soils. Prodigious seed production is also a culinary benefit to several bird species, including Goldfinches and may lead to ample and perhaps unwanted self-sowing.

Coreopsis verticillata, the Whorled Tickseed is another garden worthy species and has proven to be far longer-lived than its cousin. In fact, it actually spreads slowly via a rhizomatous root system to form a respectable groundcover. This species is predominantly found in dry open woodlands from Maryland south to Georgia, although populations have been found as far west as Oklahoma and as far north as Quebec and Ontario. The plant was once again named by Linnaeus in 1753 with the species epithet coming from the Latin Verticillus meaning whorled. The species and common name describe how the leaves, progressing from base to tip, gradually rotate around the stem such that no leaf is directly above and shading the leaf below. The plants consist of closely spaced, slender upright stems to 2–3' tall that are clothed with very narrow, oppositely arranged foliage. Each leaf is actually divided into 3 narrow leaflets, each approximately ⅛" wide by 2–3" long. The narrow leaflets give the plant a very fine textured appearance. The stems are crowned by clusters of 1–2" diameter golden yellow flowers, opening from late June through early September providing soils do not become excessively dry.

Zoom in Coreopsis 'Moonbeam'.
Picture 3: Coreopsis verticillata 'Moonbeam'.

Coreopsis 'Moonbeam', (as seen in Picture 3) is undoubtedly the most popular cultivar of Tickseed that also happens to have one of the most puzzling histories. It is a chance seedling of unknown parentage, although it is often listed as a cultivar of Coreopsis verticillata. The selection mysteriously began to appear at random nurseries during the 1950's and perhaps even earlier. A rosarian, author and gardener by the name of Léonie Bell who lived near the town of Conshohocken PA, acquired a plant around 1960 from a neighboring gardener, Mr. Howard Chidester. He, had purchased the as yet unnamed plant from a Farm Stand outside of Toms River, NJ. Léonie Bell in turn shared a division with Donald Allen of Barre Vermont, who operated a rock garden nursery named Sky-Cleft Gardens. Highly impressed, he quickly propagated enough plants to offer it in his 1965 catalogue. When he asked Léonie what it should be named, she wrote back "Oh, something with moon in it", honoring the abundant pale-yellow flower this plant produces. As a result, in 1965 the cultivar 'Moonbeam' was born! Oddly, the plant still remained relatively unknown, living in the 'horticultural shadows' so to speak. Fast forward to the 1980's. Dr. Nicholas Nickou, a physician and famed horticulturist in Branford Connecticut received a plant from Edward Alexander, a taxonomist at the NY Botanic Garden. Dr. Nickou in turn shared it with his good friend, author and nurseryman Fred McGourty of Norfolk Connecticut. Fred promoted it at his nursery, Hillside Gardens and actively distributed it to the nursery trade. From this point forward it finally claimed the spotlight and was named the Perennial Plant of the Year in 1992!

Zoom in Coreopsis 'Zagreb'.
Picture 4: Coreopsis verticillata 'Zagreb' as groundcover.

Coreopsis 'Moonbeam' is sterile and since it yields no seed, it blooms unabated from June through September. Unlike true Coreopsis verticillata, 'Moonbeam' does not have rigid, upright stems. Rather, by midsummer the plant develops a gracefully mounding habit to 18" tall and somewhat wider. The foliage is a rich dark green and very slender, almost needlelike although it is soft to the touch. To top it off, the pale-yellow flower color readily blends with nearly any neighboring color, making this is a true garden winner! It really makes a gardener wonder why it took so long to gain notoriety! The one drawback is the shortened life span when located in rich, moist soils. In fact, in overly fertile soils, the plants behave as an annual! If provided with well-drained gritty soils and lower fertility, plants have been known to thrive for years! Although often listed under the species verticillata it is actually a cross, perhaps with Coreopsis rosea or Coreopsis rosea forma leucantha. Unfortunately, the true story of its parentage and where the plant originated will probably never be known.

Zoom in Coreopsis tripteris.
Picture 5: Coreopsis tripteris at Mt. Cuba.

Another outstanding selection is Coreopsis verticillata 'Zagreb' (featured in Picture 4). It was introduced in 1997 from, oddly enough, the Department of Ornamental Plants and Landscape Architecture at the University of Zagreb in Croatia. It is a very compact plant, growing to 1' tall and slowly spreading via the rhizomatous roots to 3' in diameter over 10 years. It makes a very effective and weed free groundcover. The 1–2" diameter flowers have golden yellow ray florets surrounding central disc florets with a dark center (as seen in Picture 1). The foliage is a much lighter green than its cousin, 'Moonbeam', turning a light yellow come fall. Like 'Moonbeam' and Coreopsis grandiflora, 'Zagreb' will flourish best in full sun, although a few hours of dappled shade is not an issue. Soils should be gritty and well-drained, with sufficient organic matter to not become excessively dry or wet in winter.

Unlike the previous two species, Coreopsis tripteris is a far taller species and in my opinion, far too little seen in Gardens. Commonly called Tall Tickseed based on its 3–8' tall stature (as seen in Picture 5 at Mt. Cuba), this species also differs from its cousins by naturally growing in moist meadows and along streams. Furthermore, the flowers are sweetly scented and the foliage often assumes attractive red and auburn fall colors. The plants are native from Florida west to Texas, north to Ontario and Quebec. Yet again named by Linnaeus in 1753, the species epithet is a mix of the Latin Tri for three and Pterus for wing or feather. It refers to the appearance of the foliage, which is divided into 3 or 5 narrow leaflets, up to 5" long by ¾" wide that resemble feathers (Picture 6).

Zoom in Coreopsis tripteris.
Picture 6: Coreopsis tripteris, close-up of foliage.

The 1½–2" diameter flowers provide for a very long display, starting in late July and continuing well into September. They are arranged in an open cyme configuration, whereby the flower of the central stem or peduncle opens first, followed by the flowers of the lower, more well-branched peduncles. Each cyme is usually around 12" in diameter. This creates a more ethereal appearance than the previous two species, which have a far denser floral display. The flowers have clear yellow ray florets and brown disc florets with red or purple overtones (as seen in Picture 7 and 8). The central disc florets appear more tufted in this species and when the flower is studied closely, it is evident the stigmas are longer and more prominent. Typical to the genus, the tip of each stigma is split down the center creating two lobes. In this case the lobes curl around fully to create a circle and give the organ a key-like shape! In soils that are moisture retentive yet well-drained, the plants average 4–5' in height and the stems remain sturdy. If overly fertilized or if the soil remails too moist, plant heights may stretch to 8', often resulting in the plant collapsing. Plants can be kept shorter and more branched through pinching back the tips in May or early June.

Zoom in Coreopsis tripteris.
Picture 7: Coreopsis tripteris, close-up of stigmas.

The selection named 'Gold Standard' was introduced by Mt. Cuba in 2015 from seed collected in Alabama and grown in their trial garden. It was selected for its length of bloom and an attractive form. All plants are rhizomatous and will slowly spread to 24" in diameter. They are also known to freely seed about the garden and certain sap-sucking beetles can be problematic some years during June as they converge around and kill the youngest growth. In the garden, they can be mixed with taller ornamental grasses and can provide attractive seasonal screening. If placed next to a path or a patio the sweet scent of the flowers can also be appreciated. Seriously, what could be better?

There are obviously, many more species and cultivars for gardeners to consider, including some that feature pink and bicolor flowers. However, the species and selections mentioned herein will provide a variety of heights, textures, fragrance and even a touch of horticultural mystery, allowing the summertime garden to come alive. Yes, the common name may not conjure up images of beauty, but Coreopsis is indeed a preferred plant, providing great beauty and attracting only praise for the Garden.

Special Note: I would like to thank Ms. Carol Hanby, Dr. Nicholas Nickou's longtime friend and partner and Ms. Julie Arriens, Dr. Nickou's daughter for the information relating to the history of Coreopsis 'Moonbeam'. I would also like to thank Richard Weir III of Cornell Cooperative Extension (now retired) for his assistance in facilitating the contacts.

Picture 8: Coreopsis tripteris flower.