Penn State Perennial Trials Top 20 & Promising New Plants

Robert Berghage and Jim Sellmer

The Penn State Horticulture trial garden has been one of the premier cultivar evaluation gardens since it¹s founding in the 1930¹s.The program has evaluated thousands of annual flowers and vegetables since then, providing commercial producers and home gardeners with independent appraisals of garden performance. In 1995 the trials were expanded to include a regular perennial examination program. Evaluating perennials is more of a challenge than annuals. Annual evaluations are completed in a single season while perennial appraisals can, and should last many seasons. Plants may live for only a few years or may survive for decades. Performance of many perennials improves over a number of years after planting. Survival may be limited by cold winters or hot summers and the longevity of any cultivar may be greater or less depending on individual seasons. Extreme winters or summers may kill otherwise adapted cultivars.

Garden performance is critical to consumer acceptance of any new plant. The new interest in perennials has led to an explosion of new cultivars. Many of these plants have not been adequately evaluated in all of the areas where they are being sold. Consumer satisfaction and the continued growth of the perennial market depends on providing the consumer with the best adapted cultivars for their growing conditions.

The Penn State perennial evaluations are a multi-year program where plants are evaluated for at least three years. Plants are evaluated for flowering, foliage, uniformity, and overall form and appearance. Plants are given a numerical rating for each evaluation criteria from 1 to 5, where:

Plants are evaluated every 2 weeks during the growing season (May ­ September) The number of plants surviving in the spring is recorded as well as the height and width of each plant at the end of the growing season. Comments are also recorded for each plant in the trial. Plants are photographed and results and photographs are placed in a fully searchable database on the internet to provide access to the results. Over 200 cultivars are currently in the evaluation program, with over 100 in their third or 4th growing season. A planting block generally contains 6 ­ 15 plants of a cultivar. The trial garden is located on the Penn State campus in University Park PA. in USDA zone 5b-6a (heat zone 5-6) and Sunset climate zone 42. The trial garden is in an open level location on the edge of campus. Plants are fertilized as needed based on soil tests. Irrigation is provided using overhead sprinklers as needed. Plants are grown in full sun and not protected in the winter except by weed control mulch applied in the spring.

Some of the best plants in their 3rd or 4th growing season of evaluation (2 to 4 winters) are listed below. They have all performed well with little loss over winter or during the summer. Table 1 summarizes the ratings for each of these plants. The ratings are averages for 3 or 4 growing seasons. The height and width data are averages of 1998 and current growth.

Achillea
Anthea is a vigorous but very compact yarrow with attractive silver foliage and white flowers. These plants have improved each year in the garden. The compact form means that this cultivar resists lodging and is less invasive than most yarrow. Colorado is a vigorous yarrow with a range of pastel flower colors. It is mildly invasive and subject to lodging. The garden performance of this plant has been very consistent for the last 3 years.

Alchemilla mollis
Thriller is an outstanding spring perennial with consistent performance. It has yellow flowers in May to June forming a "cloud" of light color over very attractive foliage. The plant declines in the hot and dry weather of August in central Pennsylvania but survives to reappear the next season.

Astilbe
Sprite is a very small Astilbe that has improved each season in the garden. The flowers are an attractive pink and the spent flowers, while not as attractive as when the plant is in bloom do not really detract much from the appearance

Leucanthemum
Snowcap is the most uniform white daisy I have seen. The plants bloom all at once with stunning effect. When in bloom this is one of the most spectacular plants in the garden.

Coreopsis
Golden Gain has deep yellow gold flowers that are held above the foliage canopy. The plants could be more uniform but overall have been consistently attractive from July into August.
Moonbeam is an outstanding plant. Its¹ one shortcoming has been that many of the pale yellow flowers open under and within the leaf canopy.

Echinacea
Magnus is an attractive coneflower but the flower color, form and plant habit could be more consistent. A seedling population will produce some outstanding plants with bright flower petals and good upright habit. But other plants will have a more faded color and the petals will droop as is characteristic of the species.

Eryngium
Blaukappe has purple "thistle like¹ flowers on purple highly branched stems. It makes a great cut flower and is used in Europe for this purpose. This plant is very attractive from a distance, which is good since it attracts so many bees that most garden visitors are reluctant to get too close. Interestingly most of the insects I have observed on these plants are European Honeybees. Considering the problems with honeybees in recient years it may be possible to market this plant based on it¹s attractiveness as a food source to these insects.

Helianthemum
Annabel produces a profusion of pink flowers on abundant ground-covering foliage in the spring. This plant retains it¹s foliage in the winter (turns a dusky silver green) providing winter interest in the garden.

Heuchera
Pewter Moon is a vigorous and very attractive plant with outstanding leaf coloration. The upper surface has a metallic "pewter¹ color between dark green veins. The lower leaf surface is a bright purple-red. This plant has improved each season it has been in the garden.

Kniphofia
Flamenco is marginally hardy in central Pennsylvania with a few plants not returning after their first season. Loses in subsequent seasons have been less. It has the advantage of blooming (although somewhat feebly) in it¹s first season in the garden. The return bloom in subsequent years is much stronger than that first season.

Lobelia
Fan Scarlet is a hybrid lobelia with red tinted foliage and scarlet flowers. Several plants did not return after the first winter, but there have been no subsequent losses. The 2nd year flowering was strongest with weak flowering last year.

Perovskia
Russian sage is one of the most vigorous and consistently outstanding plants in the garden. Its shortcoming is its size, which increases every year. Consumers should be warned that the pretty little plant they buy in your garden center needs lots of room in their gardens.

Persicaria
Dimity is an attractive groundcover in the summer and winter. In the summer the pink flower spikes which turn red-brown as they mature form from June through August. In the winter the (dead) foliage turns a distinctive copper brown.

Pulsatilla
Papageno and ŒRote Glocke¹ are both outstanding in early spring with attractive flowers and seed heads. The plants remain attractive during the summer with highly disected leaves providing textural interest in the garden.

Salvia
May Night has abundant deep blue flower spikes in May-June. The seed heads are not very attractive so this plant needs to be deadheaded after flowering.

Stokesia
Parasols is a super-prolific flower producer in July with the odd bloom both before and after. This plant has been consistent and trouble free.

Verbascum
Sunset Shades is a very "Victorian" plant with tall flowering spikes covered with small pastel blossoms in the spring. It will re-bloom if cut back. The foliage is not very attractive but the flowers at least in part make up for the weedy look when the plant is not in bloom.

The plants listed below and in Table 2 have been in the garden 2 growing seasons (1 winter). This is too short an evaluation period to be very confident of perennial performance but these plants have shown outstanding merit in the time we have been watching them and are well worth mentioning.

Campanula
Chettle Charm bloomed for the first time this spring and was outstanding. This was a 45-mph plant this spring; that is to say it was a plant that people stopped in to look at after driving past the garden.

Coreopsis
Tequila Sunrise has attractive golden flowers on variegated foliage. Only 3 plants were planted and 1 failed to establish but the remaining 2 are very interesting. This plant is probably hardy only to zone 5b.

Gaura
Siskiyou Pink has filled in the bed and is producing numerous flowering stems this season.

Potentilla
Ron McBeath is a vigorous spreading plant with bright red flowers.

Polemonium
Brise D¹ Anjou has variegated foliage and blue flowers in the spring. I have heard reports of this plant not overwintering but we had no losses last winter.

Salvia sclarea var. Turkmenistan
This plant has been extraordinary vigorous in its¹ second growth season, producing numerous flowering spikes with very attractive bracts subtending each flower.

The plants in table 3 were outstanding but short-lived in the garden, surviving only 2 or 3 seasons. Aquilegia and Digitalis plants died in the summer, while the Penstemon were lost over the winter.

Aquilegia
Music is available in a number of pure colors, bicolors, or as a mix. The plants were spectacular in their 2nd and 3rd seasons but have generally declined after about 3 years.

Digitalis
Apricot this plant is a spectacular biennial with outstanding large pastel apricot flower spikes.

Penstemon
Ruby was a very attractive plant with numerous bright red flowers that did not survive its¹ second winter.

Table 1. Best 20 performing perennials in the Penn State trials. These plants have been in the garden for 3 or 4 growing seasons and 2 to 4 winters
	Cultivar	Source	First Season	Peak month	Peak rating	Average rating	Height (in)	Width (in)
Achillea hybrid
	Anthea	Blooms of Bressingham N.A.	1997	July	3.7	3.4	20	16
Achillea millefolium
	Colorado	Jelitto	1996	July-August	4.4	3.4	34	21+
Alchemilla mollis
	Thriller	Benary	1996	May-June	4.3	3.3	18	21+
Astilbe
	Sprite	Green Leaf	1997	July	5.0	4.1	16	11
Leucanthemum x superbum
	Snow Cap	Blooms of Bressingham N.A.	1997	July-August	4.7	4.1	18	21+
Coreopsis verticilata
	Golden Gain	Blooms of Bressingham N.A.	1997	July-August	4.3	3.6	19	20+
	Moon Beam	Green Leaf	1997	July-August	5.0	4.0	16	29+
Echinacea purpurea
	Magnus	Jelitto	1996	August	4.2	3.0	28	16
Eryngium planum
	Blaukappe	Jelitto	1996	July	4.2	3.6	30	19+
Helianthemum nummularium
	Annabel	Blooms of Bressingham N.A.	1997	May-June	5.0	3.5	9	28+
Heuchera
	Pewter Moon	Skagit Gardens	1997	June-August	4.2	4.0	18	14
Knipofia (Tritoma)
	Flamenco	Benary	1996	June-August	3.7	2.8	30	28
Lobelia speciosa
	Fan Scarlet	Benary	1996	August	3.6	3.0	36	16
Perovskia atriplicfolia
	Russian Sage	Green Leaf	1997	July-August	5.0	4.1	40	30+
Persicaria affinis
	Dimity	Blooms of Bressingham N.A.	1997	July-August	4.2	3.5	7	16+
Pulsatilla vulgaris
	Papageno	Jelitto	1996	April-May	4.0	2.5	12	14+
	Rote Glocke	Green Leaf	1997	April-May	4.4	3.0	13	16+
Salvia nemorosa
	May Night	Green Leaf	1997	May-June	4.6	3.8	17	20+
Stokesia laevis
	Purple Parasols	Skagit Gardens	1997	July	4.3	3.3	17	19+
Verbascum x hybrida
	Sunset Shades	Pan American Seed	1997	May-June	4.5	2.8	25	16

Information provided by Rob Berghage and Jim Sellmer Penn State Department of Horticulture, Ornamental Horticulture Extension Specialist, 103 Tyson Building, University Park, PA 16802, (814) 863-2571

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