Yes, many types of coreopsis bloom all summer from June through October when you deadhead them. Without this upkeep, most types stop by midsummer once they set seed. Your care is what gives you four full months of bright blooms in your beds instead of just two.
The coreopsis blooming season changes based on which species you grow. USDA Forest Service data shows lance-leaf types bloom from April through July in warm zones. UF/IFAS notes spring through fall bloom across types based on your climate. Threadleaf types start later in June but keep going longer into fall for you. Large-flowered types burst into heavy bloom early but fade fast if you skip deadheading your plants.
I tested this on my Zagreb threadleaf coreopsis last summer. The plants started blooming in mid-June and I gave them a hard trim in mid-July. I cut them back by about one-third with hedge shears. Fresh blooms came back within two weeks. I trimmed again in late August and got another round of flowers that lasted through the first frost in October. That gave me four full months of flowers from one planting with just two quick trims.
The idea behind deadheading is simple. When a flower fades and starts making seed, your plant shifts all its energy into those seeds. Cutting spent flowers before seeds form tells the plant to make more buds instead. Shearing threadleaf types works better than picking one flower at a time. These plants make hundreds of tiny blooms. One pass with your hedge shears takes 30 seconds instead of 20 minutes of picking stems one by one.
The longest blooming coreopsis in my garden are the threadleaf types Zagreb and Moonbeam. Both give you waves of flowers from early summer through fall with two trims during the season. Zagreb makes bright golden flowers while Moonbeam gives you softer pale yellow blooms for mixed borders. Mt. Cuba Center trials gave these two types top marks for long bloom times.
Your large-flowered types need a different method for deadheading than your threadleaf ones. Snip each spent stem back to a side branch or leaf node instead of shearing the whole plant. These types have fewer but bigger flowers so a mass shearing would leave ugly gaps in your display. Cut each stem as soon as the petals start to fade. A new bud will grow at the next node below where you made your cut. When I first grew large-flowered types I sheared them like my threadleaf plants. The result looked terrible for weeks until new growth filled back in.
Hold back on fertilizer if you want your longest bloom season. A heavy dose of nitrogen pushes leaf growth and cuts down on flower buds forming on your plants. One light feeding in early spring is all your coreopsis needs from you. Don't feed again during the summer or you'll get more leaves and fewer flowers.
Give your plants full sun, lean soil, and steady deadheading and they'll make golden blooms from June right through to your first hard frost of fall. The effort you put into trimming spent flowers pays you back in extra months of color. Your garden will still have bright blooms in September when most other flowers have faded for the season.
Read the full article: Coreopsis Plant Care and Growing Guide
