Coreopsis ‘Jethro Tull’

October 16, 2008 - 13:05

Are you looking for an eye-catching plant that is sure to get everyone’s attention? With its incredible display of bright-yellow, fluted blooms, coreopsis ‘Jethro Tull’ may be the plant you are looking for. ‘Jethro Tull’ is a recent introduction from ItSaul plants that has great potential for growers, garden centers and gardens alike. It is a natural cross between ‘Early Sunrise’ and ‘Zamphir’ and offers broader petals, a compact plant habit and an extended bloom time.

‘Jethro Tull’ forms attractive clumps reaching 12-15 inches tall by 18 inches wide and sets the landscape ablaze from early to mid-summer with tons of large, yellow, uniquely fluted blooms that surround darker, button-like centers. It grows best under partial to full sun and is hardy in USDA Hardiness Zones 4 to 9 and AHS Heat Zones 12 to 1. Tickseed is used as accent plants, border plants, mass plantings, patio containers and cut flowers.

Propagation

Coreopsis ‘Jethro Tull’ is vegetatively propagated by tip cuttings by a limited number of licensed propagators, and self-propagation is strictly prohibited. Rooted liners are available in various sizes, from 72-cell liners to 21/2-inch pots. A listing of the current licensed propagators is provided at the end of this article.

Production

‘Jethro Tull’ is well suited and most commonly produced in 1-quart to 1-gallon containers. For best performance, plant one plug liner into each pot filled with a good-quality, well-drained peat- or bark-based growing medium. The pH of the media should be maintained between 5.6 and 6.4. Many commercially available growing mixes work well provided there is good water holding ability and adequate drainage. Tickseed prefers to be grown in a moist ­— not wet — growing medium.

Coreopsis requires an average amount of irrigation; they do not tolerate really wet conditions or overly dry conditions. Water as needed when the plants are young and becoming established. Once they are well rooted, more frequent irrigations will need to be applied. When irrigation is needed, thorough watering is recommended: Ensure that the entire growing medium is wet or nearly saturated. Allow them to dry slightly between irrigations.

They are moderate feeders; growers commonly deliver nutrients using water-soluble or controlled-release fertilizers. Growers using water-soluble fertilizers apply 75- to 100-ppm nitrogen with every irrigation or use 200 ppm as needed. Growers using controlled-release fertilizers attain the best results by incorporating at a rate equivalent to 1 pound of nitrogen per yard of growing medium. For example, if the time-release Are you looking for an eye-catching plant that is sure to get everyone’s attention? With its incredible display of bright-yellow, fluted blooms, coreopsis ‘Jethro Tull’ may be the plant you are looking for. ‘Jethro Tull’ is a recent introduction from ItSaul plants that has great potential for growers, garden centers and gardens alike. It is a natural cross between ‘Early Sunrise’ and ‘Zamphir’ and offers broader petals, a compact plant habit and an extended bloom time.

‘Jethro Tull’ forms attractive clumps reaching 12-15 inches tall by 18 inches wide and sets the landscape ablaze from early to mid-summer with tons of large, yellow, uniquely fluted blooms that surround darker, button-like centers. It grows best under partial to full sun and is hardy in USDA Hardiness Zones 4 to 9 and AHS Heat Zones 12 to 1. Tickseed is used as accent plants, border plants, mass plantings, patio containers and cut flowers.

Propagation

Coreopsis ‘Jethro Tull’ is vegetatively propagated by tip cuttings by a limited number of licensed propagators, and self-propagation is strictly prohibited. Rooted liners are available in various sizes, from 72-cell liners to 21/2-inch pots. A listing of the current licensed propagators is provided at the end of this article.

Production

‘Jethro Tull’ is well suited and most commonly produced in 1-quart to 1-gallon containers. For best performance, plant one plug liner into each pot filled with a good-quality, well-drained peat- or bark-based growing medium. The pH of the media should be maintained between 5.6 and 6.4. Many commercially available growing mixes work well provided there is good water holding ability and adequate drainage. Tickseed prefers to be grown in a moist — not wet — growing medium.

Coreopsis requires an average amount of irrigation; they do not tolerate really wet conditions or overly dry conditions. Water as needed when the plants are young and becoming established. Once they are well rooted, more frequent irrigations will need to be applied. When irrigation is needed, thorough watering is recommended: Ensure that the entire growing medium is wet or nearly saturated. Allow them to dry slightly between irrigations.

They are moderate feeders; growers commonly deliver nutrients using water-soluble or controlled-release fertilizers. Growers using water-soluble fertilizers apply 75- to 100-ppm nitrogen with every irrigation or use 200 ppm as needed. Growers using controlled-release fertilizers attain the best results by incorporating at a rate equivalent to 1 pound of nitrogen per yard of growing medium. For example, if the time-release fertilizer formulation is 15-9-12, meaning it contains 15 percent nitrogen, the grower would need to incorporate 6.7 pounds of this product per yard of media to obtain 1 pound of elemental nitrogen (6.7 pounds product x 15 percent = 1.005 pounds nitrogen). Controlled-release fertilizers can also be used by topdressing at the medium recommended rates.

With its compact habit, controlling coreopsis’ height is not usually necessary when producing under greenhouse conditions. Plant stretch can often be reduced by providing adequate spacing between the plants. If controlling plant height is necessary, several commercially available PGRs are effective at controlling plant height when applied at appropriate rates, frequency and timing. Effective products and rates for most parts of the country are daminozide (B-Nine or Dazide) at 2,500 ppm, paclobutrazol (Bonzi, Paczol or Piccolo) or uniconazole (Concise or Sumagic) at 5 ppm. It may be necessary to make two to three applications seven days apart to obtain adequate control.

Insects and Diseases

Although coreopsis can be produced relatively insect free, aphids, leafhoppers, slugs, spider mites, thrips and whiteflies often can be observed feeding on them. Of these, aphids are more likely to become problematic. All of these pests can be detected with routine crop monitoring; control strategies may not be necessary unless the scouting activities indicate actions should be taken. Many growers implement a proactive strategy during the growing season by applying spray applications of systemic insecticides containing the active ingredients acetamiprid, dinotefuran, imidacloprid, pymetrozine or thiamethoxam to provide approximately four weeks of control.

The most common diseases of coreopsis are Alternaria, Botrytis, Cercospora, downy mildew, powdery mildew and Verticillium. Of these diseases, powdery mildew is the most prevalent. By managing the environment through proper plant spacing, adequate air movement and humidity controls, the occurrence of powdery mildew can be reduced. If desired, growers also can follow a preventive spray program using the appropriate chemicals: Azoxystrobin, myclobutanil, piperalin, trifloxystrobin and triflumizole are all effective products to rotate in preventive programs.

Forcing

Blooming plants of coreopsis ‘Jethro Tull’ can be easily grown throughout the spring and summer months.

It does have an obligate cold requirement and will not flower without a cold treatment. I have observed crops that were of saleable size, but with no flowers, in the late summer; these plants originated from unrooted cuttings from Central America in the early spring, and neither the stock plants nor rooted cuttings received a cold treatment. For summer sales periods, verify that your starting materials have been vernalized before purchasing them to avoid the production of nonflowering crops.

Coreopsis are obligate long-day plants, absolutely requiring long days to flower. With natural photoperiods of less than 14 hours, they will not flower. It is recommended to provide at least 14-hour photoperiods or night-interruption lighting when the natural photoperiod is less than 14 hours.

The amount of time to produce flowering plants after vernalization and the proper photoperiod are provided is a function of temperature. Coreopsis ‘Jethro Tull’ grown at 68° F will take eight to nine weeks to reach flowering, while plants grown at 60° F will flower in 11 to 12 weeks. Growing them with cooler production temperatures increases the overall production time, slightly increases the size of the flowers produced and increases the intensity of their coloration. Conversely, warmer temperatures (above 70º F) will hasten plant and flower development, but also reduces the number of flowers produced. The best plant quality is achieved when they are grown at 64-68º F.

Availability

Coreopsis ‘Jethro Tull’ is brought to the market by ItSaul Plants in Alpharetta, Ga. (www.itsaulplants.com). Currently, rooted liners are available from several licensed propagators: Walters Gardens, Zeeland, Mich. (www.waltersgardens.com); Skagit Gardens, Ore. (www.skagitgardens.com), Sunny Border Nurseries, Berlin, Conn. (www. sunnyborder.com); and Yoder Brothers, Lancaster, Penn. (www.yoder.com).

About The Author

Paul Pilon is a horticultural consultant, owner of Perennial Solutions Consulting (www.perennial-
solutions.com) and author of Perennial Solutions: A Grower’s Guide to Perennial Production. He can be reached at (616) 366-8588 or paul@perennial-solutions.com.

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