There are several commercially grown plants that fall into more than one product category; Caryopteris divaricata ‘Snow Fairy’ is an herbaceous perennial that grows and performs like a shrub but can be marketed under either horticultural category. The most distinguishing characteristic of ‘Snow Fairy’ is its striking green-and-white variegated foliage. Unlike many variegated plants, the leaves of ‘Snow Fairy’ remain clean and fresh throughout the growing season. The leaves are scorch resistant, and this plant is also drought tolerant once established in the landscape. Small lavender-blue flowers appear on terminal and axillary clusters from the late summer into the early fall.
Originally native to the Himalayas, ‘Snow Fairy’ is a recent introduction from Japan. It thrives in locations with full sun throughout USDA Hardiness Zones 5-9 and reaches 3 ft. tall and 3 ft. wide at maturity. Once established, caryopteris is heat and drought resistant but will not tolerate wet sites. It is commonly used as a filler plant in borders or mass plantings as a specimen plant or container planting, and it can be used in place of shrubs in the landscape. With few cultural problems and its ease of production, ‘Snow Fairy’ is a must-have in the landscape.
‘Snow Fairy’ is vegetatively propagated by tip cuttings. Moisten the well-drained rooting media prior to sticking the cuttings. The use of rooting hormones is optional, since caryopteris will root readily with or without the use of these substances. Stick the cuttings into the growing mix so that the lower node is at least half an inch beneath the surface of the rooting medium. Place the cuttings under low misting regimes for the first 7-10 days of propagation. When possible, it is usually best to propagate them under high humidity levels (90-percent relative humidity) with minimal misting. Gradually reduce the misting as the cuttings begin to root, and remove it altogether as soon as possible. A liner takes about 4-6 weeks to become fully rooted and ready for transplanting with soil temperatures of 68-73° F during propagation. It is beneficial to begin feeding using 100- to 150-ppm nitrogen with each irrigation beginning 10 days from sticking.
For container production, caryopteris ‘Snow Fairy’ is suitable for gallon-size containers. They perform best in a well-drained growing medium, preferably a nursery-type mix (bark-based) rather than traditional greenhouse (peat-vermiculite) blend, as they do not tolerate overly wet growing conditions. When planting, the plugs should be planted so the original soil line of the plug is even with the surface of the growing medium of the new container.
They are light to moderate feeders. Fertility can be delivered using water soluble or controlled release fertilizers. Growers using water-soluble fertilizers apply 150- to 200-ppm nitrogen as needed or feed with a constant liquid fertilization program using rates of 75- to 100-ppm nitrogen with every irrigation. Growers commonly apply time-release fertilizers as a top-dress onto the media surface using the medium rate on the product’s label, or incorporate them into the growing medium prior to planting at a rate equivalent to 1-1¼ lbs. of nitrogen per yard of growing medium. The pH of the media should be maintained between 5.7 and 6.4.
‘Snow Fairy’ requires an average amount of irrigation and is not tolerant of overly wet growing conditions. Root rot is likely when the root zone remains too wet. When irrigation is required, water them thoroughly and allow the substrate to dry slightly between waterings.
With its growth habit, it is often necessary to manage plant height during production. The height of caryopteris can often be effectively controlled by providing adequate spacing between the plants or by withholding irrigation and nutrients. Many growers manage height by trimming the plants, by removing the top third of the growth and allowing them to reflush slightly before they are sold.
Generally, ‘Snow Fairy’ is relatively insect and disease free. Spider mites are the most common insect observed feeding on caryopteris. Routine scouting will allow for early detection of these pests and can be useful in determining whether control strategies are necessary.
Growers also occasionally observe root rots such as Pythium and Phytopthora.
Root roots usually occur when improper cultural conditions are present. For example, using growing mixes that do not drain well or improper watering practices (overwatering) are the most common conditions that promote these diseases. Providing and managing the proper environment in the root zone are the most effective methods of preventing root rot diseases from occurring. If chemical controls are necessary, it is best to properly identify the pathogen(s) present before applying fungicides. Products containing azoxystrobin, dimethomorph, etridiazole, fludioxonil, mefenoxam and thiophanate methyl effectively control the most common root rot pathogens.
With its eye-catching variegated foliage and late-season flowering, most growers producing caryopteris do not market them as flowering plants. I’m not aware of any research regarding the specific forcing requirements of this plant. Nonflowering plants can be produced throughout the growing season by planting 72-cell or larger plug materials and allowing 9-11 weeks at 65° F to fill out the container.
Caryopteris divaricata ‘Snow Fairy’ is widely produced and readily available to the industry as rooted liners and finished containers. Many plant brokers will be able to help you locate this variety in its various forms and sizes.