October 2002

Coreopsis ‘Limerock Ruby’ Hybrid Tickseed By Paul Pilon

Coreopsis ‘Limerock Ruby’ is destined to become one of the most sought-after perennials for growers and gardeners across the country. Limerock Ruby yields abundant, 1 1/2-inch, ruby red, daisy-like flowers with yellow eyes, above neat, narrow foliage that resembles the leaves of Coreopsis verticillata ‘Moonbeam’, only they are slightly wider. Flowering typically begins in June, and the plant keeps blooming until early fall. Discovered by Mary Ann Faria of Limerock Plant Farms in Lincoln, R.I., this hybrid coreopsis with unknown parentage brings a new bright red flower to a genus that is dominated by various shades of yellow blooms. With these characteristics and ease of production, Limerock Ruby has the potential to be a classic American perennial.

Limerock Ruby grows best under full sun and will spread 30-36 inches over two seasons, while maintaining a height of 12-18 inches. It is hardy in Zones 4-9 with American Horticulture Society (AHS) Heat Zones 12-1. As with other varieties in the genus coreopsis, Limerock Ruby is native to the United States. It is used in perennial borders, for color accent in mixed beds and also performs well in patio containers.

Propagation

Limerock Ruby is vegetatively propagated by tip cuttings. Propagation without a license is prohibited as the plant patent is pending. There are numerous licensed propagators across the country distributing this variety in various sizes of plugs.

Production

For best performance, plant Limerock Ruby in a well-drained media, preferably a nursery-type mix (bark-based) rather than traditional greenhouse media (peat-vermiculite). Not only is the porosity (drainage) of the media beneficial during crop production, it is essential to successfully over-winter this variety of coreopsis, as it does not tolerate wet soils for long durations. The pH of Á the media should be maintained between 6.0-6.5.

Limerock Ruby is a light to moderate feeder, requiring a controlled-release fertilizer incorporated at a rate equivalent to one pound of nitrogen per yard of growing medium or 50-100 ppm nitrate delivered under a constant liquid fertilizer program.

Coreopsis requires an average amount of irrigation, as it does not tolerate really wet conditions or overly dry conditions. When watering is required, I try to water thoroughly and allow the substrate to dry slightly between waterings. If Limerock Ruby is grown under excessively dry conditions or periods of unusually high temperatures, a burn or discoloration of the flower petals may appear.

Limerock Ruby is a fast-growing cultivar and can reach shippable size in a 1-gallon container in six weeks when started from a 72-cell plug and grown at 64° F.

The bloom on this variety keeps going and going, lasting throughout the entire summer. Once the initial flush of flowers begins to subside, I have found that cutting or removing the top third of the plant will rejuvenate growth and flowering, often producing a completely new, full flush of blooms within a 3-week time period. This may also be used if plants reach an undesirable size. Simply “mow and grow.”

Potential Problems

When grown with adequate spacing and proper growing conditions, it is usually not necessary to apply chemical growth regulators to Limerock Ruby. However, my own trialing indicates that in the Northern United States, both B-Nine at 2,500 ppm or Sumagic at five ppm have shown adequate control of plant height when two applications are applied seven days apart.

Limerock Ruby, like most cultivars of coreopsis, does not have many insect pests. Various species of aphids seem to be the most prevalent insect to feed on coreopsis. Aphids can easily be controlled with various chemicals as soon as they are detected. I have had great success using insecticidal soaps combined with various pyrethroids such as Decathlon or Talstar. Another excellent option would be a preventative application of Marathon to provide season-long control of aphids.

There are very few diseases that will become problematic for the production of this coreopsis. The three most common diseases I have observed (and only on occasion) are powdery mildew, downy mildew and Botrytis.

When it comes to powdery mildew or downy mildew, an early and proper diagnosis is critical to successful control. Powdery mildew can occur on any above-ground plant tissue, and usually appears as small white, talcum-like colonies at first, but under the right conditions may engulf the plant with a “powdery” appearance. Downy mildew usually appears first on the undersides of the leaves as a mass of white or gray spores, and often the upper leaf surface (directly above where the spores are observed) will appear mottled, discolored or blistered. Please note the chemicals used to control both powdery and downy mildews are usually not the same.

Botrytis most often occurs where there is a dense plant canopy or during the late stages of the over-wintering process. To control this disease, it is best to manage the environment by providing proper plant spacing, adequate air movement, controlling the humidity, or if desired, following a preventative spray program.

Forcing

Producing flowering Limerock Ruby out of season is relatively easy, provided a few guidelines are followed. Generally, it is recommended to cool (vernalize) plugs or small containers of coreopsis for 6-10 weeks at 40° F. The cooling period enhances uniformity and reduces the time it takes to reach flowering. After the cooling is achieved, provide photoperiods of 16 hours by extending the day if necessary, or use a 4-hour night interruption during the middle of the night, providing a minimum of 10 foot-candles of light at plant level.

Limerock Ruby is an obligate long-day plant and will flower under long days regardless of the vernalization time. The time it takes to reach flowering depends on the growing temperature after the plants are placed under long-day conditions. Plants grown at 65° F will flower in about 10 weeks, while plants grown at 72° F will flower in as little as eight weeks. For larger flower size, more flowers and shorter plants, grow at cooler temperatures. For the supplier nearest you, contact Blooms of Bressingham or The Flower Fields.