Perennials Demystified: Taking the Fear out of Premium Cultivars

Paul Pilon

The perennials finished growers produce are often placed into two categories: “Bread and Butter” and “Premium.” Bread-and-butter perennials are those varieties that have been commoditized. Premium perennials, on the other hand, are high-end and typically genetically superior to other varieties on the market, but are more expensive and are produced for premium programs at a higher price point.

Many finished growers are hesitant to produce premium perennials in fear of production failures and losing money from higher-priced starting materials if things don’t go right during production.

Finishing Echinacea

Keep the liners moist until they’re ready to transplant. Water them well just prior to transplanting.
Avoid overwatering. Too much irrigation decreases their rate of growth and makes them more susceptible to diseases.
Provide 100 ppm nitrogen with every irrigation or 200 ppm as needed.
Aphids, leafhoppers, slugs and whiteflies are the primary pests.
Botrytis commonly occurs from late fall through late winter on foliage while overwintering and may infect the crowns. Provide excellent ventilation and low humidity (less than 80% RH) during this period.
Aster yellows is an irreversible, viral-like disease that causes yellowing of the leaves, reddening of the plant, stunting and deformed flowers. Discard any plants showing these symptoms.
Applications of the growth regulator Configure can be applied to promote branching. Apply 300 to 600 ppm twice at 14-day intervals.

Flowering Requirements for Seed Varieties

Flowering occurs the most rapidly and uniformly when they’re grown under constant, 14-hour daylengths.
Seed cultivars are short-day/long-day plants. Bulking plants under 9-hour daylengths for 6 to 8 weeks before exposure to long days (14 hours) improves crop quality.
It takes 10 to 13 weeks from the beginning of long days to flower at 68 to 72F (20 to 22C).

Recommended Seed-Grown Cultivars: PowWow Wild Berry, Prairie Splendor

Flowering Requirements for Vegetative Varieties

Short daylengths will cause the plants to maintain a compact rosette growth habit.
For bulking or sizing up the plants, produce them under 24-hour daylengths using daylength extension lighting. This keeps them actively growing and non-flowering.
Ideally, obtain liners from a supplier who provides 24-hour lighting in their production program.
Once the plants have bulked up, they can be exposed to long days to promote flowering. Fourteen hours is the best daylength for flowering echinacea.
For late spring to early summer sales, it’s best to provide daylength extension rather than night interruption lighting.
It takes 10 to 13 weeks from the beginning of long days to flower at 68 to 72F (20 to 22C).

Recommended Vegetatively Grown Cultivars: Butterfly Kisses, Julia

Finishing Brunnera

Plant soil line of the liner even with the soil line of the final container.
Requires an average amount of irrigation. Keeping them too dry will result in leaf scorch. Conversely, overly wet conditions lead to crown rots.
Brunnera are light feeders, requiring only 50 to 75 ppm nitrogen with every irrigation or 150 ppm as needed.
Leaf scorch can also occur under high-light intensities. Provide 35% to 55% shade between mid-April and early September.
Aphids and slugs are the primary pests.
Crown and root rots including Fusarium, Phytopthora and Thielaviopsis are the primary diseases.
Requires vernalization for flowering.
After vernalization, it takes 4 to 5 weeks to flower at 60 to 65F (15 to 18C).

Recommended Cultivars: Jack Frost, Emerald Mist

Finishing Helleborus

Use large starting materials to reduce the incidence of juvenility and improve the uniformity of bloom.
Juvenility is more prevalent with seed strains.
Transplant liners in the late spring the year before they’re needed for sales.
Requires an average amount of irrigation. Never allow Helleborus to wilt. Avoid overwatering them during the summer months when the rate of growth is reduced.
They’re moderate feeders. Apply 100 to 150 ppm with every irrigation while the plants are actively growing.
Maintain light levels below 6,000 footcandles. Provide 50% to 70% shade during the summer months.
Watch for aphids, Botrytis and powdery mildew.
Requires vernalization for flowering.
After vernalization, grow under natural daylengths.
Flowers early with cool temperatures.

Recommended Cultivars: Winter Thrillers series, Penny’s Pink

Finishing Heuchera

Do not bury the crown when transplanting.
Average water requirement. Avoid moisture extremes.
Light to moderate feeders; 75 to 100 ppm nitrogen with every irrigation. Avoid excessive salts.
Grow under light shade. Cultivars with green to yellow foliage are more sensitive to high light intensities and chemical applications.
Aphids, Phytopthora and Rhizoctonia are the primary pests and diseases.
Most cultivars require vernalization for flowering. Often marketed as a foliage perennial.
Bulk in the final container for at least 6 weeks before overwintering them.
After vernalization, it takes 6 to 9 weeks to flower at 60 to 65F (15 to 18C). GP

Recommended Cultivars: Caramel, Obsidian

Paul Pilon is a horticultural consultant, owner of Perennial Solutions Consulting (www.perennialsolutions.com) and author of “Perennial Solutions: A Grower’s Guide to Perennial Production.” He can be reached at paul@perennialsolutions.com or (616) 366-8588.