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These plants range from 46–120 cm (18–47 in) in height. The flowers are usually yellow with a toothed tip, but may also be yellow-and-red bicolor. They have showy flower heads with involucral bracts in two distinct series of eight each, the outer being commonly connate at the base. The flat fruits are small and dry and look like insects.
There are 75–80 species of Coreopsis, all of which are native to North, Central, and South America. The name Coreopsis is derived from the Greek words κόρις (koris), meaning "bedbug", and ὄψις (opsis), meaning "view", referring to the shape of the achene.
Coreopsis species are a source of nectar and pollen for insects. The species is known to provide food to caterpillars of some Lepidoptera species, including Coleophora acamtopappi. The sunny, summer-blooming, daisy-like flowers are popularly planted in gardens to attract butterflies. Both annual and perennial types are grown in the home garden (USDA Hardiness Zone 7a/6b). In the Mid-Atlantic region, insects such as bees, hover flies, and wasps are often observed visiting the flowers.
All Coreopsis species were designated the state wildflower of the U.S. state of Florida in 1991. In the language of flowers, Coreopsis means to be always cheerful, while Coreopsis arkansa in particular stands for love at first sight.
Coreopsis is a variable genus closely related to Bidens. In fact, neither Coreopsis nor Bidens, as defined in the 20th century, is strictly monophyletic. Coreopsis is best described as paraphyletic. Previously (1936), Coreopsis was classified into 11 sections and 114 species, but the African species were subsequently reclassified as Bidens, leaving the North and South American species, some 75–80 in all, under Coreopsis. 45 species are in the 11 North American sections, and the remaining 35 are in the South American section Pseudoagarista. The North American species fall into two broad groups, with 5 sections and 12 species in Mexico and North America and the remaining 5 sections and 26 species in Eastern North America. 
One group which does seem to be monophyletic consists of temperate species from North America, including five sections of Coreopsis, Bidens coronata and Bidens tripartita, and the genus Thelesperma (five species). 
Distribution and habitat
North American Coreopsis can be found in two habitats in the wild, growing along roadsides and open fields throughout the Eastern United States and Canada. In this environment the plant will self-sow.
Coreopsis can grow in a garden as a border plant, or in a container, preferring well-drained soil. Deadheading the flowers ensures it does not become weedy. Using the USDA Hardiness Zones will identify what soil and climate is preferred for different cultivars or species. Notable species found in cultivation are C. grandiflora and C. verticillata, as well as their various cultivars.
- Coreopsis sect. Pseudoagarista (35)
- Coreopsis cyclocarpa S.F.Blake
- Coreopsis bicolor
- Coreopsis leavenworthii Torr. & A.Gray – Leavenworth's tickseed
- Coreopsis paludosa M.E.Jones
- Coreopsis tinctoria Nutt. – plains coreopsis
- Coreopsis auriculata L. – lobed tickseed
- Coreopsis basalis (A.Dietr.) S.F.Blake – goldenmane tickseed
- Coreopsis grandiflora Hogg ex Sweet – large-flowered tickseed
- Coreopsis intermedia Sherff – goldenwave tickseed
- Coreopsis lanceolata L. – lance coreopsis, lance-leaf tickseed
- Coreopsis nuecensis A.Heller – crown tickseed
- Coreopsis nuecensoides E.B.Sm. – Rio Grande tickseed
- Coreopsis pubescens Elliott – star tickseed
- Coreopsis wrightii (A.Gray) H.M.Parker – rock tickseed
- Coreopsis floridana E.B.Sm. – Florida tickseed
- Coreopsis gladiata Walter – coastalplain tickseed
- Coreopsis integrifolia Poir. – fringeleaf tickseed
- Coreopsis linifolia Nutt. – Texas tickseed
- Coreopsis nudata Nutt. – Georgia tickseed
- Coreopsis rosea Nutt. – pink tickseed
Section Gyrophyllum (syn. Palmatae)
- Coreopsis delphiniifolia Lam. – larkspurleaf tickseed
- Coreopsis major Walter – greater tickseed
- Coreopsis palmata Nutt. – stiff tickseed
- Coreopsis pulchra F.E.Boynton – woodland tickseed
- Coreopsis tripteris L. – tall tickseed
- Coreopsis verticillata L. – whorled tickseed
- Coreopsis douglasii (DC.) H.M.Hall – Douglas's tickseed
- Coreopsis californica (Nutt.) H.Sharsm. – California tickseed
- Coreopsis stillmanii (A.Gray) S.F.Blake – Stillman's tickseed
South America, 35 species
- Coreopsis mcvaughii D.J.Crawford
- Coreopsis petrophila A.Gray
- Coreopsis petrophiloides B.L.Rob. & Greenm.
- Coreopsis rudis (Benth.) Hemsl.
- Coreopsis bigelovii (A.Gray) Voss – Bigelow's tickseed
- Coreopsis calliopsidea (DC.) A.Gray – leafstem tickseed
- Coreopsis hamiltonii (Elmer) H. Sharsm. – Mount Hamilton tickseed
- Coreopsis latifolia Michx. – broadleaf tickseed
- Coreopsis gigantea (Kellogg) H.M.Hall – giant coreopsis
- Coreopsis maritima (Nutt.) Hook.f. – sea dahlia
Formerly placed here
- "Genus: Coreopsis L." Germplasm Resources Information Network. United States Department of Agriculture. January 6, 2011. Archived from the original on June 29, 2011. Retrieved February 9, 2011.
- Sunset Western Garden Book, 1995:606–607
- "Coreopsis For the Mid-Atlantic Region Research Report". December 2015. Retrieved 27 January 2017.
- Kim, Seung-Chul; Daniel J. Crawford; Mesfin Tadesse; Mary Berbee; Fred R. Ganders; Mona Pirseyedi; Elizabeth J. Esselman (September–July 1999). "ITS sequences and phylogenetic relationships in Bidens and Coreopsis (Asteraceae)". Systematic Botany. 24 (3): 480–493. doi:10.2307/2419701. Check date values in:
- Quattrocchi, Umberto (2000). CRC World Dictionary of Plant Names: A-C. CRC Press. p. 615. ISBN 978-0-8493-2675-2.
- Main, Martin B.; Ginger M. Allen. "Florida State Symbols". Electronic Data Information Source. University of Florida IFAS Extension. Retrieved February 9, 2011.
- "Language of Flowers - Flower Meanings, Flower Sentiments". www.languageofflowers.com. Archived from the original on 2016-11-24. Retrieved 2016-11-26.
- Crawford, D. J.; Mort, M. E. (2005). "Phylogeny of Eastern North American Coreopsis (Asteraceae-Coreopsideae): insights from nuclear and plastid sequences, and comments on character evolution". American Journal of Botany. 92 (2): 330–6. doi:10.3732/ajb.92.2.330. PMID 21652409.
- "tickseed". USDA plants website. USDA NRCS National Plant Data Team. Retrieved 27 January 2017.
- "Species Records of Coreopsis". Germplasm Resources Information Network. United States Department of Agriculture. Archived from the original on January 20, 2009. Retrieved February 9, 2011.
- "Coreopsis". Integrated Taxonomic Information System. Retrieved June 6, 2010.