The care information provided in this section represents the kind of practical advice is available for all the plants in this web site if you subscribe to the monthly customized newsletter Yardener’s Advisor.
Coreopsis plants are very drought tolerant. In fact, they do not respond well to continuously moist soil. However, when they are first planted they need regular watering--an inch of water a week from rain or from a garden hose or soaker hose system--until they become established.
If you have good soil with lots of organic matter added each year and if your plants are well mulched, you will need to water them only when it has not rained for a week or two. If you have poor soil with little organic content or if you choose not to use mulch, then you may have to water the plants every few days in summer heat, at least until they are well on their way. This is especially true for coreopsis growing in containers that dry out quickly in the sun. For information on products see the file on Choosing Watering Equipment
Coreopsis do not require a highly fertile soil, and feeding them too much makes them tall and floppy. A half-handful of general purpose slow acting granular fertilizer scattered on the soil or worked into the soil around each plant in the spring is plenty for the season. They will do well in most soils without any fertilizer at all. For more information see the file for Choosing Fertilizers
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A 1 or 2 inch layer of an attractive organic material like wood chips, chopped leaves, shredded bark or dried grass clippings spread on the soil around the base of coreopsis plants will help control weeds. Mulch also reduces soil moisture loss through evaporation, and cools the soil. Best of all, the organic mulch gradually decomposes and adds organic matter to the soil, it improves its nutrition, structure and drainage. For more information see the file on Using Mulch
Coreopsis are quite self-reliant, needing very little attention. To prevent indiscriminate reseeding be sure to cut off faded flowers. This will also stimulate more flowering. To control the spread of coreopsis, dig up overlarge clumps and divide them every 3 or 4 years into smaller individual plants to replant and give away. To encourage reseeding, allow the last flush of flowers to remain and dry on the plant in the fall.
Some of the taller coreopsis types may benefit from support as they grow to full height and confront summer rainstorms. Fashion supports from stakes placed around the outer edges of the flower clump joined by unobtrusive string. Or, use commercial plant supports designed for large plants such as peonies. For more information see the file Staking Flowers