December 2015 Culture

Perennial Solutions: Tiarella ‘Jade Peacock’ By Paul Pilon

Most perennials are fairly one dimensional, providing their strongest showing for a limited time or during a single season of the year. Tiarella, on the other hand, delivers a strong showing throughout the year offering interesting and attractive displays in each of the four seasons. The recent introduction ‘Jade Peacock’ from Proven Winners exemplifies the traits a perennial for all seasons should have.

‘Jade Peacock’ emerges with bright chartreuse foliage with deep red centers in the spring, which matures to a jade green coloration with deep purple centers as the seasons progress. Spikes of light pink flower buds appear in the late spring, opening to creamy white, lightly fragrant starlike blossoms. As winter approaches, the evergreen foliage turns deep
mahogany purple with black centers.

It thrives in locations with partial to full shade throughout USDA Hardiness Zones 4 to 9, generally outperforming most of the old standbys. The plants grow 8-10 inches tall with a spread of about 20 inches when they are mature. When blooming, the flower spikes rise above the canopy, maintaining an attractive, yet tidy appearance; the total height while in bloom is 12-14 inches. ‘Jade Peacock’ has an extended bloom time, flowering from spring to early summer.

With its contrasting foliage patterns and attractively dissected leaves, ‘Jade Peacock’ is a great plant for shady landscapes. This great perennial not only provides year-round interest when used in borders and mass plantings in the landscape, it also can be grown and marketed as an appealing container plant or component of mixed containers. If you haven’t tried tiarella in recent years, ‘Jade Peacock’ is a great cultivar to start with.

Propagation

Tiarella ‘Jade Peacock’ is vegetatively propagated by means of tissue culture. Since a plant patent is being sought (PPAF – Plant Patent Applied For), unlicensed propagation of this cultivar without permission of the applicant is currently prohibited.

Licensed propagators carefully transfer the stage III plantlets into the individual cells of the liner trays they are rooting them into. Place them under a moderate misting regime for the first few days they are in the propagation house. Rooting occurs best when they are propagated under high humidity levels (90 percent relative humidity) with minimal misting. Avoid providing too much misting or rooting may be inhibited and diseases can develop. Gradually reduce the amount of misting being provided each day. They usually only require misting for the first six to 10 days. A liner takes approximately four to six weeks to become fully rooted and ready for transplanting.

Production

Tiarella ‘Jade Peacock’ is well suited for production in 4- to 5-inch pots or gallon containers. It performs best when grown in moist, well- drained growing mixes; many peat- and bark-based growing mixes work well. When transplanting, the liners should be planted so the original soil line of the liner is even with the surface of the growing medium of the new container. Avoid planting them too deeply (do not bury the crown) as poor plant establishment, reduced vigor and crown rot may result.

The amount of irrigation to provide varies slightly over the production cycle. Initially, keep the root zone uniformly moist until the roots reach the outside of the root ball. Once rooted, they can dry out slightly between irrigations. While being grown in containers, they can tolerate dry, but not drought-like growing conditions. Foam flowers do not tolerate being kept wet for extended periods. When they are kept too moist, the foliage may turn slightly chlorotic and crown rots could develop.
When irrigation is required, water thoroughly and allow them to become moderately dry between irrigations.

Tiarella perform best when grown with light to moderate fertility levels. Growers using water-soluble fertilizers commonly provide 75- to 125-ppm nitrogen plus micronutrients with each irrigation or 150- to 250-ppm nitrogen as needed. Controlled-release fertilizers can be incorporated into the growing mix before planting using the equivalent of 1 pound of elemental nitrogen per cubic yard of growing mix or top dressed using the medium labeled rate. During production, maintain slightly acidic conditions with the pH between 5.5 and 6.5.

When growing ‘Jade Peacock’ in the late winter or early spring for spring sales, it is not necessary to grow them under shade as the light intensities are naturally low this time of year. However, as spring progresses and the natural light levels become more intense, it is beneficial to provide some shade to keep them actively growing and to prevent the leaves from becoming scorched. Reducing the light levels by 35-50 percent is usually sufficient.

Tiarella ‘Jade Peacock’ has a compact growing habit and does not usually require height management strategies. However, under certain circumstances, such as when they are grown at high plant densities or when ‘luxury’ nutrient levels are being delivered, it may be necessary to implement height control strategies. If toning is necessary, the plants can be sprayed with 5-ppm uniconazole (Concise or Sumagic); one to two applications applied seven days apart should suffice.

Insects and Diseases

There are only a few pests that attack or diseases which infect Tiarella. Aphids and whiteflies are the most prevalent insects observed feeding on them from time to time. As mentioned previously, crown and root rots caused by Phytopthora, Pythium and Rhizoctonia can occur. These pathogens are usually secondary to other factors such as improper planting depths, high fertility levels or saturated growing conditions. Botrytis is another disease to watch for particularly during the overwintering period. Routine scouting is helpful for detecting the presence of insects and diseases early and for determining if and when control strategies are necessary.

Scheduling

Tiarella ‘Jade Peacock’ is generally marketed in bloom from early spring to early summer. It can also be sold as a foliage perennial throughout the year. Tiarella does not require vernalization for flowering (cold beneficial) and ‘Jade Peacock’ does flower prolifically without cold. However, when growing them in large container sizes (1 gallon), it is recommended to plant foam flowers into the final container during the late summer or early fall; this allows them to bulk up and promotes faster, more uniform flowering in the spring. This is my preferred strategy as it results in the fullest containers.

An alternate approach would be to plant tiarella in the spring using vernalized liners. Plant 72-cell liners into 4- to 5-inch pots and larger 30-cell liners into gallon containers. They can be grown under natural daylengths with 24-hour average temperatures of 65° F. When growing them in this manner, the 4- to 5-inch containers will be marketable in six to seven weeks while the gallon pots will be ready in eight to 10 weeks. Using liners which have not been vernalized will usually take slightly longer to bloom.

Availability

Tiarella ‘Jade Peacock’ is marketed by Proven Winners (www.provenwinners.com). Liners are available from Walters Gardens Inc. (www. waltersgardens.com) and through several of the licensed Proven Winner propagators (www. pwcertified.com/grower/purchase/propagators. cfm).