Coreopsis is a native North American plant with a wide range, growing naturally from Alaska to the southern tip of Florida. By selecting the right species, growers can find anything from USDA-Zone-3-hardy varieties to those that tolerate weeks of 100°F-plus temperatures.
Coreopsis is useful in bedding schemes and can provide a nice foil for bold-leaved plants like heuchera. The vast color range allows them to be married with many foliage colors. They should not be forgotten when it comes to putting together fall containers, as the pumpkin- and orange-toned flowers work well with kale and squash.
Coreopsis Culture Tips
These varieties are great component plants and add a new color range for the container market. Different varieties require different culture. Use these guidelines when growing coreopsis:
Media: Coreopsis prefers a well-drained media such as a 60/40 peat-perlite or peat-pumice mix. Drainage is absolutely essential to this genus, and high-peat mixes can drown a plant.
Planting: Plant one 72-cell liner per 4-inch, 6-inch or gallon pot and two liners per pot for larger sizes. Coreopsis is not as sensitive to planting depth as other plants, since they readily root up the stem. It is advisable, however, to make sure that the top of the liner matches evenly with the top of the soil in the pot to prevent stem and crown rot. Fungicides at planting are usually not necessary.
pH/EC: Maintain a pH of 5.5 to 6.5 and an EC of 1.5 to 2.0 via the pour-through method.
Temperature: A 50°F to 55°F night and a 70°F to 75°F day temperature are ideal for coreopsis.
Light: Coreopsis requires full sun and grows best with 35 to 50 mol/m²d.
Fertilizer/Watering: Supply a low to medium rate of constant liquid feed at 100 to 150 ppm nitrogen of 20-10-20. Too much nitrogen will cause lush, soft growth that is more susceptible to disease. Make sure to dry down plants between irrigations because wet-dry cycles prevent root-rot pathogens. All coreopsis require excellent drainage. If overwintered in containers, the plants will need to be kept fairly dry.
Pinch/PGRs: Pinching the plants one week post-planting helps produce a well-branched, full plant with more flowers. Mechanical pinching can be replaced by the use of Florel at 200 to 400 ppm. For growers who are new to Florel or coreopsis, it is recommended to apply at the lower rate with more frequent applications. For example, two applications at 200 ppm, one to two weeks apart instead of once at 400 ppm. Remember that efficacy of Florel is dependent on the pH of the spray solution (needs to be 4.0 to 4.5) and the length of time the solution is allowed to dry.
Pests/Disease: Aphids, mites and thrips are the major insect pests of coreopsis. As with any crop and pest, scouting and prevention are keys to success. Make sure to rotate chemical controls to prevent resistance. Powdery mildew is the most prevalent disease of coreopsis. Prevention is essential when combating powdery mildew, as it often discolors entire leaves.
Although powdery mildew will rarely kill plants, the white discoloration on leaves quickly makes them unmarketable. Be sure to give these plants plenty of light and space for proper airflow. Apply fungicides preventatively. The following chemicals have proven effective for controlling powdery mildew on coreopsis: Heritage, Pageant, Palladium and KleenGrow for conventional growers and Milstop for organic growers.
Propagation: Rooting of URCs is relatively simple and will usually finish a 72-cell in two weeks, possibly three if under winter conditions. Since these are long-day plants, propagation is best accomplished under short days, whether they are provided by natural day-length or with black cloth. Mist is usually only required for the first five to seven days, depending on environmental conditions. Rooting hormone is not required, but is beneficial, and a rate of 500 ppm IBA works well. Terra Nova Nurseries’ Conor Carey prefers to use K-IBA, since it is easy to prepare and store. It is also a huge labor savings when sticking by using the spray-drip down method.
Scheduling: Finish time from 72-cell liner to 4-inch pot is four to six weeks. From 72-cell to 1 gallon pot is eight to 10 weeks.