August 2012 Culture

Perennial Solutions: Carex oshimensis ‘Everest’ By Paul Pilon

Many growers produce and market ornamental grasses in conjunction with their perennial programs. There are numerous types of grasses in production today. Most are true grasses such as miscanthus and panicum; however, some plants being marketed as ornamental grasses are actually not even related to grasses (family Gramineae). Carex belongs to the sedge family Cyperaceae. Only a handful of sedges from the genus carex are being commercially produced today.

Although the differences between sedges and grasses can be difficult to distinguish, there are some characteristics that can be used to differentiate between the plants from these two families. The most obvious characteristic is the flower stems; grasses have mostly round, hollow flower stems with nodes, whereas the flower stems of sedges do not have nodes and are triangular. Additionally, the flowers of grasses are perfect (both male and female flowers on the same flower) and sedges have separate male and female flowers on the same plant. For those die-hard taxonomists, another distinguishing characteristic is the ligules; most grasses have conspicuous ligules (appendages at the junction of the sheath and blade), while sedges do not have ligules.

Carex oshimensis ‘Everest’ is a recent introduction that has several characteristics that appeal to both commercial growers and landscapers. ‘Everest’ was discovered by Pat Fitzgerald of Ireland’s FitzGerald Nurseries Ltd. as a sport from the well know C. oshimensis cultivar ‘Evergold’.

‘Everest’ has striped evergreen foliage with distinctive silvery white edges that forms attractive 12- to 18-inch mounds. Carex prefers moist but well-drained soils in sheltered locations with full sun to semi-shade. Avoid locations with extended periods of saturated soils. Once established, it offers good tolerance to dry conditions and is cold hardy throughout USDA Hardiness Zones 5 to 8.

Ease of production, low maintenance, good plant vigor, along with a compact clumping habit, are characteristics that make ‘Everest’ a good candidate for mixed containers, patio pots, or to brighten up perennial beds and borders.

Propagation

Carex are vegetatively propagation tissue culture or by plant division. ‘Everest’ is a patented plant; therefore unauthorized propagation of this cultivar is strictly prohibited.

Production

Carex ‘Everest’ is best suited for production in 1-gallon or smaller-sized containers using a single liner per container. When transplanting, they should be planted so the original soil line of the liner is even with the surface of the growing medium of the new container. Carex performs best when they are grown in a moist, well-drained medium with a slightly acidic pH: 5.8 to 6.2. They require an average amount of irrigation and do not tolerate extended periods of saturated conditions. It is best to keep them moderately moist, but not consistently wet.

Carex requires light to moderate amounts of nutrients during production. Fertility can be delivered using water-soluble fertilizers; feeding at rates of 75- to 125-ppm nitrogen with each irrigation or 250-ppm nitrogen as needed. Controlled-release fertilizers can also be used to deliver nutrients using low to medium-label rates; typically incorporating with rates delivering approximately 1.0 pound of elemental nitrogen per yard of growing medium.

Many growers have found it beneficial to grow ‘Everest’ in facilities covered with 35 to 55 percent shade cloth. Shade is particularly beneficial after transplanting to remove stress until the plants become established or when they are being produced during the months of the year with the highest light intensities (mid-April and early September).
With its compact habit, it is not necessary to control plant height using plant growth regulators. In most cases, plants of a desirable shape and size can be obtained when they are grown at an adequate plant spacing.

Pests and Diseases

Insect or disease problems are generally a rare occurrence when growing carex ‘Everest’. Aphids, mealybugs and slugs are the primary insect pests that may occasionally be observed feeding on them, but rarely do these pests become problematic. Rust and crown/root rots are the most common diseases growers are likely to observe. Improper planting practices or poor irrigation management are often responsible for the onset of root or crown rot pathogens that growers experience. Growers can obtain early detection of insects and diseases when they utilize routine scouting programs; the results can be used to determine if and when control strategies are necessary.

Forcing

Carex ‘Everest’ produces a high-quality plant whether it is in bloom or not; however, with its variegated foliage, it is most commonly marketed as a foliage item in perennial assortments or ornamental grass programs.

For early season sales, it is best to provide a bulking phase and start them in the late summer or early fall and overwinter them. In general, allow six to eight weeks of good growing temperatures before allowing the plants to go dormant. After overwintering, the plants can be flushed to a marketable size inside heated or unheated structures. With 24-hour average temperatures of 60° F inside these facilities, carex will reach a marketable stage in seven to eight weeks.

For mid- to late-season sales, liners can be obtained and transplanted during the same growing season. It takes slightly longer to fill out the container when planting liners in the spring. The time to finish also varies with the size of the liner used as the starting materials. One-gallon containers grown from 72-cell liners and produced with 24-hour average temperatures of 70° F will finish in about nine to 10 weeks.

Smaller-sized starting materials will take slightly longer to fill out the containers.

Availability

Carex oshimensis ‘Everest’ is available from a number of licensed propagators including Pacific Plug & Liner (www.ppandl.com) and Skagit Gardens
(www.skagitgardens.com).