Perennial Solutions: Heucherella ‘Autumn Cascade’
Heucherella is an intergeneric cross between heuchera and tiarella. They’ve become increasingly popular, but are still overshadowed by the popularity of heuchera, one of its parents. Originally, heucherella cultivars were much like their parents and formed attractive mounded habits, but in recent years breeding efforts have led to the selection of cultivars with trailing habits.
Heucheralla ‘Autumn Cascade’ is one of the latest trailing introductions from Terra Nova Nurseries. It was developed by Janet N. Egger of Danby, Oregon. ‘Autumn Cascade’ has soft shades of brick red to reddish tan leaf colorations, cutely lobed foliage and a low growing, trailing habit. The foliage only reaches 4 to 6 inches in height but easily spreads to 3 feet across. The 14-inch tall spikes with tiny white bell-shaped flowers appear in the spring.
This variety can be grown throughout Zones 4 to 9. ‘Autumn Cascade’ performs well in a wide range of growing conditions ranging from full sun to full shade. The best leaf coloration is achieved when they are grown under partial shade. Areas with some shade are recommended for hotter climates. With higher light intensities, some leaf scorch may be observed; this can be reduced somewhat by maintaining consistent moisture levels.
‘Autumn Cascade’ is very versatile and can be used in perennial borders, patio pots and mixed containers. With its trailing habit, ‘Autumn Cascade’ can also be used by itself or as a component in hanging baskets or used as a groundcover or in mass plantings.
Heucherella ‘Autumn Cascade’ can be propagated easily using vegetative cuttings. A plant patent is being sought; therefore, unlicensed propagation of this cultivar without permission of the applicant is currently prohibited. However, unrooted cuttings are available to the industry for propagation (royalties are required).
Stick the cuttings into liner trays containing a pre-moistened, well- drained growing medium or stabilized substrate. The use of rooting compounds is not essential, but can slightly reduce the rooting times and increase the rooting percentages.
Maintain moderate mist frequencies for the first two days of propagation, then provide a low misting regiment until the cuttings have rooted. Over-misting and saturated media will cause the cuttings to lose nutrition, delay rooting and can promote the development of plant pathogens. When possible, it’s best to propagate under high humidity levels (90 percent relative humidity) with minimal misting. At seven to 10 days after sticking, it’s beneficial to apply water-soluble fertilizers using 75- to 100-ppm nitrogen at each irrigation or at least once per week.
With soil temperatures ranging from 68 to 72o F, misting is only required for the first 13 to 18 days after they are stuck. The liners take approximately five to six weeks from sticking to become fully rooted and ready for transplanting.
‘Autumn Cascade’ is suitable for production in 1-quart up to 1-gallon containers. They perform best when grown in a moist, well-drained growing mix. When transplanting, the growing medium in the pot should be even with the top of the liner. Avoid planting too deeply or they will establish more slowly and crown rot is more likely to develop.
Heucherella generally require average amounts of irrigation. Keep them uniformly moist until they are established. While they are grown in containers, they are more prone to marginal leaf burn under high light intensities when they are also under water stress. Throughout production, avoid overly wet or dry growing conditions. When irrigation is necessary, I recommend watering thoroughly then allowing the soil to dry slightly between waterings.
They are considered to be light to moderate feeders. Nutrients can be delivered using water soluble or controlled release fertilizers. Growers using water-soluble fertilizers apply 100-ppm nitrogen with every irrigation or use 200 ppm as needed. Controlled- release fertilizers are commonly incorporated into the growing medium prior to planting at a rate equivalent to 0.9 to 1.1 pounds of elemental nitrogen per yard of growing medium or topdressed using the medium rate on the product’s label. Avoid placing the fertilizer near the crown of the plant when topdressing. The pH of the media should be maintained between 5.5 and 6.5.
It’s not necessary to use height management strategies to control plant height, but with its trailing habit, it may be beneficial to manage the width of the plants. Plant size can be managed by providing adequate space between plants and to some extent withholding irrigation and fertility. When these strategies are not providing enough reduction in plant size, plant growth regulators can be applied. Heucherella are responsive to 5-ppm uniconazole (Concise or Sumagic) applications. One or two applications applied seven days apart should be sufficient.
Insects and Diseases
here are only a few problems with insects or diseases that growers are likely to experience. Occasionally, aphids and spider mites may appear, but usually these pests only cause minimal injury to the plants. Botrytis and crown/root rots (Phytophthora, Pythium and Rhizoctonia) are the primary plant pathogens to infect heucherella. Proper planting depths and good cultural practices will usually keep these diseases from becoming problematic. Insects and pathogens can be detected with routine crop monitoring; control strategies may not be necessary unless the scouting activities indicate actions should be taken.
Temperature and Scheduling
With its colorful lobed leaves and trailing habit, ‘Autumn Cascade’ is commonly grown and marketed as a foliage perennial. Non-flowering plants can be produced easily and quickly throughout the growing season using fresh, non-vernalized liners. When transplanting from 72- cell liners and growing them with 24 hour temperatures of 65° F, it takes approximately five weeks to finish a 1-quart container and seven weeks to grow a trade 1-gallon pot.
Vernalization is required when flowering plants are desired. I find it best to bulk up and vernalize heucherella in the final container size. This can be done by planting them in the late summer or early fall prior to the spring they are intended to be sold. Provide a cold treatment of nine weeks with temperatures between 30 and 40° F prior to forcing. They are day neutral and can be grown at natural day lengths after they have been vernalized. Flowering occurs seven to nine weeks from the onset of growth when the average temperatures are 65° F.
Heucherella ‘Autumn Cascade’ is available as unrooted cuttings, which are available to “Root and Sell” licensees and Terra Nova’s broker network. Rooted liners are available from Terra Nova Nurseries and a number of its licensed propagators. Check with Terra Nova Nurseries or your broker to purchase either unrooted cuttings or liners of ‘Autumn Cascade’.