They are flashes and waves of bright yellow in the summer that are highly attractive to multiple bee species and now, thankfully, The Mt. Cuba Center has parsed the lot of native coreopsis species into understandable, usable groups. Mt. Cuba’s native perennial trialing program is designed to offer insights into the best native plants and selections for the MidAtlantic.
Their coreopsis trial ran from 2012 to 2014 and included 94 selections of hardy and non-hardy species, including 13 perennial coreopsis native to the Eastern US. Of those, five were rated at the top, with Coreopsis palustris Summer Sunshine the top rated plant. Following it in the ratings are: C. tripteris Flower Tower; C. tripteris Gold Standard; C. verticillata Zagreb; and C. verticillata Last Dance.
C. tripteris Gold Standard is a slightly smaller selection at 5.5’, showing good disease resistance. It’s a Mt. Cuba selection and currently they are working to release it into the trade.
Coreopsis is generally thought of as a short lived perennial. One of the trial’s main takeaways is that winter hardiness seems to be tied to plant form: Clumping vs. rhizomatous. In general, clumping coreopsis do not survive as well, while plants forming rhizomes were better able to tolerate wet/dry extremes.
Mt. Cuba’s recently released online pdf, Coreopsis for the Mid-Atlantic Region (2015) includes a great chart on insects observed on the top 25 coreopsis including honeybees, bumble bees, dark sweat bees, green sweat bees, hoverflies, wasps, etc. http://www.mtcubacenter.org/horticultural-research/trial-garden-research/
While you’re at the Mt. Cuba trial webpage, you can also sign up to receive trial program updates. This past summer while visiting Mt. Cuba, I saw monarda, baptisia, carex and clematis being tested. Stay tuned, there will be a pipeline of performance information to come.