2006 Herbaceous Perennial Trial Results Neil Anderson1, Associate Professor, Floriculture Mary Maguire Lerman2, Coordinator of Horticulture Programs Minneapolis Men's Garden Club2 Steve Poppe3, Horticulture Plot Coordinator Georgianna

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2006 Herbaceous Perennial Trial Results
Neil Anderson1, Associate Professor, Floriculture

Mary Maguire Lerman2, Coordinator of Horticulture Programs

Minneapolis Men's Garden Club2

Steve Poppe3, Horticulture Plot Coordinator

Georgianna Mesenbring4, Master Gardener

Libby Wilkes5, Master Gardener
USDA Zone 4

1Department of Horticultural Science

University of Minnesota

St. Paul, MN 55108

2Lyndale Park Gardens

Minneapolis Park & Recreation Board

Minneapolis, MN 55409

USDA Zone 3/4

3W. Central Research & Outreach Center

Morris, MN 56267

USDA Zone 3

4Private Trial Gardens, Grand Marais, MN 55604

5Private Trial Gardens, Lutsen, MN 55612
Visit the Trial Website: http://www.florifacts.umn.edu/

Funded, in part, by the Minnesota Agricultural Experiment Station.

2005, University of Minnesota, Minneapolis Park & Recreation Board


The trials conducted in Minnesota are the first systematic, scientific, public trialing system to evaluate winter hardiness and garden performance of herbaceous perennials. Our three-year trials are unique by testing replicated samples of seed and/or vegetatively propagated products for a duration of three years (three growing seasons and three winters). A national test system for herbaceous perennial plants does not exist. Individual breeder/producer or distributor companies may have organized public and/or private trialing of perennials. For instance, Blooms of Bressingham Perennials N.A. (Lapeer, MI) conducts performance evaluations and hardiness tests for each year’s new releases. This provides a gauge of performance/hardiness across various regions, although none are as rigorous as the Minnesota Z3-4 test sites.

We have been trialing herbaceous perennials to test for winter hardiness and garden performance since 1998. Currently, we conduct trials at five sites (USDA Z3-Z4) in Minnesota to measure performance over a three-year period.
Recent Developments.

Last year we hailed the successes from these winter hardy herbaceous perennial trials with a listing of the best and the brightest known as “Minnesota Tough and Terrific™”. A listing of the “Minnesota Tough and Terrific™” perennials (currently there are 57 plants) recommended for northern gardens is posted on the trial website. This listing will be updated each year with new perennials as they meet the criteria of performance throughout the 3-year period.

The 2007 Perennial Plant of the Year (17th) from the Perennial Plant Association (www.perennialplant.org), is Nepeta x faassenii ‘Walker’s Low’ (Cat mint). This was first introduced in 1988 (Europe) and has become very popular in recent years. We trialed in our herbaceous perennial winter hardiness trials. Due to it’s superior performance and winter hardiness (USDA Z3-8), it is now listed as a MN Tough and Terrific™ Perennial. It has blue-violet flowers with a long bloom time, sporting grey-green foliage (fragrant when crushed), and is low maintenance. It will bloom continuously if properly pruned. All cat mints attract bees, butterflies, and other pollinators. However, Nepeta are deer and rabbit resistant! Essentially, ‘Walker’s Low’ is pest and disease free. Plants grow 30”-36” tall and wide when grown in full sun. It can tolerate some shade in warmer climates. The name of this does NOT relate to plant size (it’s named after a European garden).
The 2006 Perennial Plant of the Year (16th) is Dianthus gratianopolitanus ‘Feuerhexe’ (‘Firewitch’). This is hardy in USDA Z3-9 and sports cheddar-pink flowers. It is excellent as a rock garden plant, to edge borders, put in wall crevices or on a sunny slope. The foliage is clove-like in scent and if planted as a border, it will be fragrant as people pass by. Foliage is 3’4” tall and 6-12” wide; flowers will grow to a height of 6-8”. It flowers in the spring and can rebloom in the summer and fall seasons. The name Cheddar Pink (common name) is from a gorge in England where this species is native. It was introduced to the market by Keiber & Seibert Nursery (Germany) in 1957 but wasn’t known in N. America until 1987 (Sunny Border Nurseries, CT).
The 2005 Perennial Plant of the Year (15th) is Helleborus x hybrida, Lenten or Christmas rose, a USDA Z4-9 perennial. This is the first perennial plant of the year that is not a pure cultivar; instead this represents an open-pollinated mix of flower colors. Helleborus prefer partial to full shade conditions with well-drained, humus-rich soils. They maintain their foliage throughout the growing season. In Minnesota, they typically establish best with mulch to maximize soil moisture; late summer planting is often preferred. These early spring-flowering perennials have long-lasting flowers and tolerate dry conditions once they’re established.
Note: Mark your calendars to attend the 2007 Perennial Plant Symposium - 25th Anniversary 25th Perennial Plant Symposium and Trade Show Columbus, Ohio. Dates: August 5-11, 2007. To register, go to their website (above).
Speaking of meetings worth attending, the Minnesota Nursery and Landscape Association’s (MNLA) annual convention--“Green Expo”, held in early January each year (the first Wed-Fri) in conjunction with the Minnesota Turf and Grounds Foundation, continues to be a perennial favorite both locally, regionally, and nationally! Each year there are numerous presentations on herbaceous perennials and the capacity crowds testify to the fact that the herbaceous perennial industry remains strong, filled with vitality and creativity. More than 8,000 industry professionals attend the Green Expo in January 2007. Visit the MNLA website for further information: www.mnlandscape.org. A new feature is the website www.GardenMinnesota.com, with the latest growing information and designated list serve options. Don’t forget to mark your calendars for next year’s Green Expo!

Another great feature of MNLA membership is access to the many publications. The herbaceous perennials publication, “Perennials: Plants for Outdoor Living”, was reissued with new additions, great photography, and landscaping ideas. It’s a perfect accompaniment to all sales at your retail nursery or to give to landscape customers.

For the past three years, MNLA has partially funded the expenses involved in conducting these herbaceous perennial winter hardiness trials at Morris. The University of Minnesota Agricultural Experiment Station also provides limited funding in support of these trials. We also initiated a $50/cultivar trialing fee for the 3-year program tests to for costs involved in shipping plant materials, data analyses, and the printing of this publication. We extend a hearty thank you to all funding sources.
Plant Evaluation Sites.

Five sites are incorporated into the tests; three have been established with high public visibility for exposure to consumers and Minnesota/national commercial floricultural and nursery growers/researchers, while two sites are on private land. All sites except St. Paul have sun and shade conditions. We have been testing material at St. Paul, Minneapolis, and Morris since 1998. In 2001, the Lutsen and Grand Marais trial sites were added.

Signage identifies the plant materials and the companies donating the new cultivars. Grower and home-gardener field days during the peak flowering season expose the local industry and consumers to the new introductions for on-site evaluation at St. Paul and Morris. The gardening public and growers can also rate the various plant materials on a yearly basis.

The five testing sites are as follows:

  1. Department of Horticultural Science, University of Minnesota, St. Paul. MN. USDA Z4 (Winter Hardiness Zone); Z5 (Heat Zone). At this site plant material is planted in full sun.

  2. Lake Harriet Gardens, Minneapolis Park and Recreation Board, Minneapolis, MN. USDA Z4 (Winter Hardiness Zone); Z5 (Heat Zone). This site includes both full sun and partial shade plantings.

  3. West Central Research and Outreach Center, University of Minnesota, Morris, MN. USDA Z3/4 (borderline between Z3 and Z4 for Winter Hardiness); Z4 (Heat Zone). This site includes both full sun and partial shade plantings.

  4. Private Site, Lutsen, MN. USDA Z3 (lakeside, Lake Superior); Z2 (Heat Zone). This site includes both full sun and partial shade plantings. The trials are conducted with a windbreak (a building) between the lake and the plantings.

  5. Private Site, Grand Marais, MN. USDA Z3 (higher elevation and inland from Lake Superior); Z2 (Heat Zone). This site includes both full sun and partial shade plantings.

Plant Material.

Select genera were initially designated for testing at all five sites, based on input from northern consumers, growers, and other horticultural professionals. Additional genera are now included as new releases surface with market potential that may not have been scientifically trialed for winter hardiness. The Perennial Plants of the Year, as determined by the Perennial Plant Association, are included in the trials (when available), beginning with the year 2000.

Plant materials of particular interest are new cultivars/varieties for which winter hardiness is unknown or that will be of interest to consumers and the ornamental industry. Four plants per accession (replications) are planted at each site for evaluation. Material is planted with side-by-side comparisons at each site, although the landscape plantings differ.

Plant material trialed in the sites is neither propagated nor distributed to interested parties. Rather, all interested parties are directed to contact their distributors or the original source company (breeder/producer) directly to obtain the plant material.

Weather Conditions.

Data on monthly high, low, and average temperatures, as well as precipitation totals are included for each site. This data is generated by the University of Minnesota, Department of Soil, Water, and Climate and is available on their website: http://climate.umn.edu/climatology.htm
Evaluation Criteria.

All plants (if hardy) remain at each site for three years. During each growing season, the herbaceous perennials are evaluated for various criteria. Of particular importance is winter hardiness and overall performance during and after establishment at the trial sites. The following criteria are used for evaluating the germplasm:

  1. Winter hardiness

  2. Disease and/or pest susceptibility, tolerance, or resistance.

  3. Cultural responses to cutback, growback.

  4. Plant morphology: height x width measurements, stem strength.

  5. Flowering: time of 100% flowering, duration.

  6. Reseeding or invasiveness: tendency to form asexual and/or sexual propagules, their dissemination, and competition with the parental source.

  7. Floriculture and Nursery Industry ratings: Used to make the Minnesota Select Perennial Winners.

Year Planted.

Material is received and planted from plugs, liners, or nursery containers in the spring (May-June) of each year. All plots are irrigated to promote establishment. No fall plantings occur.

2003=Plants were planted during 2003. This is the third and final year for winter hardiness ratings (many did not survive) and the fourth season for other ratings.

2004=Planted during 2004. This is the third season of flowering data and the second for over-wintering (survival).

2005=Planted during the 2005 spring season. This is the second season of flowering data and the first for over-wintering (survival).

2006=This is the first year for recording flower data and plant growth; no winter hardiness data will be collected on these until Spring, 2007. Any data included is not indicative of the accessions full potential after establishment and over-wintering. Many may not flower during the first year.

% Winter Survival.

% winter survival = [number of reps. surviving] / [total number of reps. per site] x 100. Calculated only for those plants that have over-wintered through >1 winter period.

Date of 100% Flowering.

Date when 100% of the replications at each site were in flower. If material reflowers, that is noted in the comments section.

Flower Stalk Strength.

Measured on a scale of 1-5, with 1-2 meaning weak/lodging; 3-5 denoting increasingly stronger stems.

Floral Display.

An indication of floral coverage over the plant surface area.

Exc=Excellent, 75-100% coverage

Gd=Good, 50-75% coverage

Fr=Fair, 25-50% coverage

Pr=Poor, <25% coverage

Height x Width.

Measured in centimeters (cm) at flowering.

Reseed or Invasive.

In second-year plantings, indicates seedlings or vegetative propagules surrounding original plants and tendency to become aggressive (taking over neighboring plantings) or invasive (spreading and establishing themselves as populations throughout the trial gardens via seed). If the cultivars were invasive, the seedlings/veg. propagules had achieved 100% cover in the plot and the original clones were difficult, if not impossible, to identify.


Additional notes recorded during the observational year.

2006 Results.

Winter Scene at the Z4 trial site (St. Paul) ‘My Favorite’ garden chrysanthemums creating a snow fence in mid-winter.

Herbaceous perennial trial reports for 1999-2006 are available on the web at: http://www.florifacts.umn.edu/ This is the seventh year of reporting winter hardiness and performance evaluations of herbaceous perennials in replicated trials (>4 plants/site) in USDA Z3/4 and Z4. Before 1999 and the arrival of the herbaceous perennial breeder, the first trialing year had several difficulties. In some instances, insufficient numbers of perennials were received for planting at all three sites. As a result, some plantings at Morris (Z3/4) did not occur and data may be missing for this site for various accessions.

The weather conditions during the winters of 1998 and 1999 were extremely mild and snow cover was minimal. During the 1998 evaluation season (1998 calendar year), St. Paul & Minneapolis (Z4) had a high of 88.4F and a low of 10.7F, with a maximum precipitation of 4.6" (per month). Morris (Z3/4) had a high of 82F and a low of 4.3F with a maximum of 5.7"/month precipitation. During the 1999 evaluation period, St. Paul & Minneapolis (Z4) had a high of 96F and a low of -17F, with a high of 10.3"/month. Morris (Z3/4) had a high temperature of 94F and a low of -21F, with a maximum precipitation of 4.9"/month.

During the year 2000, St. Paul & Minneapolis (Z4) experienced a high of 94F and a low of -13F with a maximal precipitation of 6.3"/month. Morris (Z3/4) had a high of 97F and a low of -20F, while the maximum precipitation was 4.5"/month. The winter season of 2000-2001 was a more typical season with normal snow cover and colder temperatures. During the year 2001, St. Paul & Minneapolis (Z4) had a high of 99F and a low of -14F with a maximal precipitation of 7.79"/month. Morris (Z3/4) had a high temperature of 98F and a low of -31F, with a maximum precipitation of 5.63"/month. Lutsen and Grand Marais (Z3) had a high temperature of 91F and a low of -13F, with a maximum precipitation of 7.45"/month.

The winter conditions of 2002-2003 were mild for temperature and snowfall until late January 2003. Unfortunately, the period of October onwards was unseasonably warm with periodic freezing/thawing cycles that normally would occur in the spring season. November – December 2002 was also extremely dry; this lack of moisture coupled with frost heaving may have caused considerable damage to unprotected herbaceous perennials (non-mulched). Spring 2003 will be noteworthy to determine which perennials were tough enough to survive the early winter abnormal weather patterns. During the year 2002, St. Paul & Minneapolis (Z4) had a high of 88.1F and a low of 17.5F with a maximal precipitation of 14.9"/month. Morris (Z3/4) had a high temperature of 85.4F and a low of 17.5F, with a maximum precipitation of 8.3"/month. Lutsen and Grand Marais (Z3) had a high temperature of 76.3F and a low of 10.3F, with a maximum precipitation of 7.1"/month.

During 2003, St. Paul & Minneapolis (Z4) had a high of 86.3F and a low of 7.3F with a maximal precipitation of 6.77"/month. Morris (Z3/4) had a high temperature of 83.1F and a low of 0.4F, with a maximum precipitation of 7.24"/month. Lutsen and Grand Marais (Z3) had a high temperature of 71.8F and a low of -6.7F, with a maximum precipitation of 3.68"/month.

In 2004, St. Paul and Minneapolis (Z4) experienced high and low temperatures of 79.8F and 2.9F, respectively, with a maximal snow depth of 11.4”. Morris (Z3/4) had a similar range in temperatures (-2.8F to 78.7F) and a lesser snow depth of 8.1”. The Z3 sites (Grand Marais, Lutsen) had a high temperature of 72.3F (no low temperature data is available) and a maximal snow depth of 19.8”.

The 2005 climate information for St. Paul and Minneapolis (Z4) showed a temperature range of -15F to 95F and a maximal snow depth of 0“. In Morris (Z3/4), the temperatures ranged from -28F to 91F with a maximum snow depth of 9“. Lutsen (Z3) and Grand Marais (Z3) had lower temperatures (ranging from -25F to 85F and -27F to 87F, respectively) and considerably greater snow depth (maxima of 51“ and 41“, respectively) which lasted throughout most of the winter months.

Our summer heat finally returned during 2006. The 2006 climate information for St. Paul and Minneapolis (Z4) showed a temperature range of -14F to 100F and a maximal snow depth of 0”. In Morris (Z3/4), the temperatures ranged from -19F to 97F with a maximum snow depth of 8“. Lutsen (Z3) and Grand Marais (Z3) had lower temperatures (ranging from -22F to 67F and -15F to 94F, respectively) and considerably greater snow depth (maxima of 8” and 8“, respectively) which lasted throughout most of the winter months.

As a consequence of the recent mild winters due to ‘el Niño’, the sites had less than adequate snow cover during 1998-2006. In Morris, with windier conditions, many of the trial gardens were completely windswept of snow when the colder temperatures occurred. This may have exposed the crowns to lower soil temperatures than would occur with adequate snow cover or the crowns may have severely desiccated. This was particularly problematic in the shade garden area, potentially causing higher winterkill in Heuchera, x Heucherella, and Tiarella. During the 2001-2002 winter, most areas of Z3-4 were relatively snow-free during October 2002 through January 2003. Soil moisture levels at the surface were dry and an extended duration of frost heaving occurred. Snowfall commenced in late January 2003 and provided protection later in the winter. Many unprotected (no mulch or other protective covering) herbaceous perennials were unable to survive the desiccating, frost-heaving, and snow-free conditions of the 2002-2003 winter period. This may have contributed, in part, to the rise in herbaceous perennial sales during the year! More importantly, the winter survival data in at least the Z4 conditions are inaccurate reflections of true cold tolerance or winter hardiness. Thus, any statements regarding the lack of winter survival during 2003, in particular, reflect this situation.

2006 Minnesota Select Perennial.

One established, this perennial had superior performance at all sites during the 2005 season. The most popular perennial with >62% winter hardiness and superior performance throughout the season is Astilbe x arendsii ‘Color Flash™’. To obtain this perennial, contact your local retailer or wholesale distributor.

Phlox paniculata ‘Volcano® Purple’. The ‘Volcano’ series from Anthony Tesselaar, Int’l. is a new dwarf and mildew-tolerant phlox which is perfect for the home gardens! We have trialed four colors in the series, ‘Volcano Purple’, ‘Volcano White’, ‘Volcano Pink with white eye’, and ‘Volcano Red’, all of which have had nearly 100% winter survival across all of Minnesota! If their performance continues, these can be sold as hardy in USDA Z3-4.

These are very tough phlox, which perform outstandingly in the garden. Their dwarf nature (24”-30” stems) means that the stalks don’t get too tall and either crowd things out or lodge (fall over) after a heavy, windy rainstorm. They’re great for garden beds, borders and containers—even parking lots. The dark, shiny green foliage is a great backdrop for the brightly colored flowers that produce a terrific appearance in the garden. Flowering continues from June through September of later. Other colors available include: ‘Volcano Ruby’ and ‘Volcano Pink with Red Eye’.

“Volcano® Phlox feature flower clusters of 125 flowers or more each, providing masses of flowers from June through September. To prolong blooming, cut back by 1/3 after the first bloom - this will encourage new stems and more flowers.” http://www.tesselaar.com/

Phlox ‘Volcano Purple’ ‘Volcano’ series

Phlox ‘Volcano White’ Phlox ‘Volcano Pink w/Red Eye’


Hardy perennials with superior performance.

For those accessions planted during 1998-2005 only, the following herbaceous perennials were found to have an average of >62% winter hardiness, high rankings in floral display, stem strength, and minimal invasiveness. These are highlighted with a dark background on the attached 2006 Trial Data (which includes only material planted in 2003-2006) or earlier Trial Data Reports (1998-; consult our website databases).

  1. Aethionema grandiflorum

  2. Agastache rupestris ‘Blue Fortune’ 2000 Minnesota Select Perennial.

  3. Aquilegia x hybrida 'Songbird Mix'

  4. Artemisia dracunculus

  5. A. lactiflora

  6. A. ludoviciana ‘Silver Queen’

  7. A. ludoviciana 'Valerie Finnis'

  8. A. schmidtiana 'Silver Mound'

  9. Astilbe x arendsii ‘Color Flash’ 2005 Minnesota Select Perennial

  10. A. x hybrida 'Sheila Haxton'

  11. Baptisia australis

  12. Bergenia cordifolia

  13. Calamagrostis x acutiflora 'Karl Foerster' 2003 Minnesota Select Perennial

  14. Fragaria sp. ‘Pink Panda’

  15. Fragaria sp. 'Red Ruby' 2001 Minnesota Select Perennial

  16. Geranium x cantabrigiense 'Biokovo'

  17. G. x cantabrigiense 'Karmina'

  18. G. macrorrhizum 'Spessart'

  19. G. macrorrhizum ‘Ingwersen’s Variety’

  20. G. spp. ‘Alan Bloom’

  21. G. spp. 'Summer Skies'

  22. Helenium sp. ‘Mardi Gras’, 2004 Minnesota Select Perennial

  23. Heliopsis helianthoides 'Loraine Sunshine'

  24. Hemerocallis x hybridus 'Lady Emily'

  25. H. x hybridus 'Lady Eva'

  26. H. x hybridus 'Lady Florence'

  27. H. x hybridus 'Lady Jackie'

  28. H. x hybridus 'Lady Rose'

  29. H. x hybridus 'Lady Scarlett'

  30. H. x hybridus 'Miss Amelia'

  31. H. x hybridus ‘Miss Mary’

  32. H. x hybridus 'Miss Mary Mary'

  33. H. x hybridus 'Miss Tinkerbell'

  34. x Heucherella hybrida ‘Raspberry Ice’

  35. x Heucherella hybrida ‘Silver Lode’

  36. Hosta x hybrida ‘Sundance’

  37. Hylotelephium x hybridum 'Autumn Joy' (formerly Sedum)

  38. H. x hybridum 'Frosty Morn' (formerly Sedum)

  39. H. x hybridum ‘John Creech' (formerly Sedum)

  40. H. x hybridum ‘Mini Joy’ (formerly Sedum)

  41. H. x hybridum ‘Rosy Glow’

  42. H. spectabile 'Brilliant' (formerly Sedum) 1999 Minnesota Select Perennial.

  43. Monarda didyma 'Marshall's Delight'

  44. Monarda didyma 'Petite Delight' 2000 Minnesota Select Perennial

  45. Nepeta x faassenii ‘Blue Wonder’

  46. N. x faassenii ‘Dropmore’

  47. N. x faassenii ‘Walker’s Low’

  48. N. sibirica ‘Souvenir d’Andre Chaudron’

  49. Phlox maculata ‘David’

  50. P. paniculata ‘Volcano Pink’

  51. P. paniculata ‘Volcano Purple’ 2006 Minnesota Select Perennial

  52. P. paniculata ‘Volcano Red’

  53. P. paniculata ‘Volcano White’

  54. Pulmonaria sp. ‘Opal’

  55. Rubus arcticus stellatus

  56. Stachys byzantina ‘Helene von Stein’

  57. Verbascum x hybridum 'Southern Charm'

Hardy perennials with sub-optimal performance.

For those accessions planted during 1998-2005 only, the following herbaceous perennials were found to have an average of >62% winter hardiness, but low rankings in floral display, stem strength, or other characters.

  1. Dianthus barbatus

  2. x Heucherella hybrida 'Cranberry Ice'

  3. x H. hybrida 'Dayglow Pink'

  4. Hylotelephium x hybridum 'Rosy Glow' (formerly Sedum)

  5. H. spectabile 'Indian Chief' (formerly Sedum)

  6. Lilium x hybridum 'Salmon'

  7. Nepeta x faassenii 'Six Hills Giant'

  8. Thymus sp.

Borderline Hardy Perennials.

Based on the data collected from plantings during 1998-2005 only, the following perennials were found to have minimal survival, i.e. 1%-50% survival in both Z3/4 and Z4 (unless otherwise noted). As such, we are classifying these as borderline winter hardy perennials. NOTE: For the winter of 2003, many ‘borderline hardy’ perennials may have died due to desiccation, due to a lack of snow cover when sub-zero temperatures occurred. With this low winter survival rating, gardeners would be advised to purchase more than one plant of each cultivar and to mulch for winter survival. Many of these may perform as annuals in the north.

  1. Agastache mexicana ‘Mauve Beauty’

  2. A. rugosa 'Honey Bee Blue'

  3. Campanula carpatica ‘Chettle Charm’

  4. Coreopsis grandiflora ‘Crème Brulee’

  5. Dianthus carthusianorum

  6. D. x hybrida ‘Corona Cherry Magic’

  7. Geranium sp. ‘Appleblossom’

  8. G. sp. ‘Rozanne’

  9. Heliopsis helianthoides ‘Bressingham Double’

  10. Hemerocallis x hybridus 'Lady Lucille'

  11. H. x hybridus 'Miss Victoria'

  12. Heuchera x hybrida ‘Brandon Pink’

  13. Hylotelephium x hybridum 'Mohrchen' (formerly Sedum)

  14. H. x hybridum ‘Raspberry Ice’

  15. H. x hybridum ‘Robustrum’ (=’Ruby Glow’)

  16. H. x hybridum ‘Vera Jameson’

  17. H. x hybridum variegata

  18. H. sp.

  19. Lilium x hybridum 'Spotted Yellow'

  20. L. x hybridum 'Orange'

  21. Perovskia abrotanoides 'Filigran'

  22. P. abrotanoides ‘Longin’

  23. P. scrophulariifolia ‘Superba’

  24. Phlox carolina ‘Miss Lingard’

  25. P. maculata ‘Eva Cullum’

  26. P. maculata ‘Miss Wilma’

  27. Stachys byzantina 'Cotton Ball'

  28. S. byzantina 'Silver Carpet'

Non-hardy Herbaceous Perennials.

The following perennials (planted during 1998-2005 only) were found to be non-hardy (0% survival) in at least one site (Z3, Z3/4 and/or Z4). If cultivars were hardy in one zone but not the others, the zone in which they were not hardy (0% survival) is listed after each name. These should be treated as annuals in the non-hardy locations.

  1. Achillea macrophylla

  2. A. wilsoniana Z3 (Grand Marais, Lutsen)

  3. A. millefolium

  4. Aethionema membranaceum Z4 (St. Paul), Z3/4 (Morris)—needs adequate snow cover to survive.

  5. Agastache barberi ‘Firebird’

  6. A. barberi ‘Tuti-Fruti’

  7. A. rugosa ‘Honey Bee White’

  8. A. rupestris ‘Apricot Surprise’

  9. A. rupestris ‘Pink Panther’

  10. A. rupestris ‘Snow Spike’

  11. Alfredia cernuum Z3 (Grand Marais)

  12. Alstroemeria x hybrida ‘Sweet Laura’

  13. A. x hybrida Jazze ‘Deep Rose’

  14. A. x hybrida Jazze ‘Purple Rose’

  15. A. x hybrida Jazze ‘Rose Frost’

  16. A. x hybrida Princess Lily ‘Angela’

  17. A. x hybrida Princess Lily ‘Daniela’

  18. A. x hybrida Princess Lily ‘Marilene’

  19. A. x hybrida Princess Lily ‘Monica’

  20. A. x hybrida Princess Lily ‘Oxana’

  21. A. x hybrida Princess Lily ‘Ragna’

  22. A. x hybrida Princess Lily ‘Sissi’

  23. A. x hybrida Princess Lily ‘Stephanie’

  24. A. x hybrida Princess Lily ‘Zsa Zsa’

  25. Anemone spp. ‘Party Dress’ Z3

  26. Anthemis sp. 'Susanna Mitchell' Z3 (Lutsen, Grand Marais)

  27. Anthriscus sylvestris ‘Ravenswing’ Z4, Z3 (Lutsen, Grand Marais)

  28. Aquilegia x hybrida 'Lime Frost' Z3 (Lutsen, Grand Marais)

  29. Artemisia lactiflora ‘Guizho’

  30. Artemisia schmidtiana Z3 (Lutsen)

  31. A. sp. ‘Huntington’ Z3/4

  32. A. sp. 'Silver Limelight' Z3 (Lutsen)

  33. A. stelleriana ‘Silver Brocade’

  34. Asclepias curassavica

  35. A. incarnata

  36. A. incarnata ‘Ice Ballet’

  37. A. tuberosa 'Hello Yellow'

  38. Aster nova-angliae ‘Alma Potchke’

  39. Astilbe x hybrida ‘Sheila Haxton’ Z4 (St. Paul), Z3/4 (Morris)

  40. Baptisia lacteal (leucantha) Z3/4

  41. Carex buchananii

  42. Carlina acanthifolia Z3 (Grand Marais)

  43. Caryopteris incana

  44. C. incana prostrate form

  45. Centaurea montana

  46. Coreopsis grandiflora ‘Early Sunrise’ Z3/4

  47. Coreopsis grandiflora 'Limerock Ruby'

  48. C. g. ‘Limerock Passion’

  49. Corydalis wilsonii Unnamed releases (15404-15408)

  50. Delphinium tatsienense Z3/4, Z3

  51. Dendranthema x grandiflora 'Sesquicentennial Sun' Z3

  52. D. x g. 'Snowscape' Z3

  53. D. x g. My Favorite 'Autumn Red' Z3

  54. D. x g. My Favorite 'Coral' Z3

  55. D. x g. My Favorite 'Yellow Quill' Z3

  56. D. x g. My Favorite 'White' Z3

  57. Dianthus carthusianorum Z4

  58. D. chinensis Bouquet Purple’ Z4

  59. D. c. 'Pixie' Z4 (St. Paul), Z3/4 (Morris), Z3

  60. D. cruentus

  61. D. x hybridus ‘Amazon Cherry’

  62. D. x hybrida ‘Amazon Rose Magic’

  63. D. x hybrida ‘Dynasty White’ Z4 (St. Paul), Z3/4 (Morris

  64. D. x hybrida ‘Dynasty Red’ Z4 (St. Paul)

  65. Dicentra eximia ‘Adrian Bloom’

  66. Digitalis lantana

  67. D. x mertonensis

  68. D. purpurea 'Alba'

  69. Echinacea sp. (purple), (white)

  70. E. pallida (=paradoxa) Z3/4

  71. E. purpurea ‘Bravado’ Z3/4

  72. E. purpurea ‘Double-decker’ Z4 (St. Paul)

  73. E. purpurea ‘Ruby Star’ Z3 (Lutsen, Grand Marais)

  74. Erigeron sp. ‘Prosperity’ Z3/4

  75. E. sp. ‘Sapphire Blue’ Z3/4

  76. Euphorbia x martinii

  77. Gaura lindheimeri ‘Blushing Butterflies’

  78. G. lindheimeri ‘Corrie’s Gold’

  79. G. lindheimeri ‘Crimson Butterflies’

  80. G. lindheimeri ‘Daphne’ (or Dauphine)

  81. G. lindheimeri ‘Pink Fountain’

  82. G. lindheimeri ‘Siskiyou Pink’

  83. G. lindheimeri ‘Sunny Butterflies’

  84. G. lindheimeri ‘Whirling Butterflies’

  85. G. lindheimeri ‘White Fountain’

  86. Geranium x cantabrigiense 'Patricia'

  87. G. x oxonianum ‘Claridge Druce’

  88. G. x oxonianum ‘A.T. Johnson’

  89. G. sp. ‘Alan Bloom’ Z4 (St. Paul)

  90. G. sp. ‘Appleblossom’ Z3/4

  91. G. sp. ‘Bressingham Purple’

  92. G. sp. 'Bressingham's Delight'

  93. G. sp. 'Rozanne’

  94. G. sp. ‘Summer Skies’ Z4—needs adequate snow cover to overwinter

  95. Helenium autumnale ‘Coppelia’

  96. Helianthemum x hybridum ‘Henfield Brilliant’

  97. Helichrysum x hybridum ‘Ruby Cluster’

  98. Helleborus niger

  99. H. odorus

  100. Hemerocallis x hybrida ‘Ruby Stella’ Z3

  101. H. x hybrida ‘Stella Supreme’ Z3 (Grand Marais)

  102. Heuchera x hybrida ‘Autumn Haze’

  103. H. x hybrida ‘Champagne Bubbles’

  104. H. x hybrida ‘Crimson Curls’

  105. H. x hybrida 'Green Spice'

  106. H. x hybrida ‘Harmonic Convergence’ Z4

  107. H. x hybrida ‘Raspberry Ice' Z3 (Grand Marais)

  108. H. x hybrida ‘Rosemary Bloom’ Z4

  109. H. x hybrida ‘Silver Lode' Z3 (Grand Marais), Z3/4 (Morris), Z4 (St. Paul)

  110. H. x hybrida ‘Strawberry Candy’

  111. H. x hybrida 'Veil of Passion'

  112. H. x hybrida 'Velvet Night'

  113. H. sanguinea ‘Bressingham Hybrid’

  114. x Heucherella hybrida 'Burnished Bronze'

  115. x Heucherella hybrida 'Cinnamon Bear'

  116. x Heucherella hybrida 'Kimono'

  117. x Heucherella hybrida ‘Quicksilver’ Z4

  118. x Heucherella hybrida ‘Silver Streak’

  119. x Heucherella hybrida ‘Viking Ship’ Z3/4

  120. Hylotelephium x hybridum ‘Larinem Park’ Z4

  121. Kniphofia sp. ‘Bressingham Comet’

  1. K. sp. 'Cobra' Z4

  1. K. sp. ‘Shining Sceptre’

  2. Lavandula angustifolia 'Lavender Lady' Z4

  3. Leucanthemum x superbum 'Angel' Z3, Z3/4, Z4 (St. Paul)

  4. L. s. 'Becky' Z3, Z3/4, Z4 (St. Paul)

  5. Lilium x formolongo 'Raizan No. 1'

  6. L. x f. 'Raizan No. 2'

  7. L. x f. 'White Lancer'

  8. L. longiflorum 'Snow Trumpet'

  9. Lupinus regalis ‘Morella Cherry’

  10. Lychnis sp. 'Jenny' Z3, Z3/4, Z4 (St. Paul)

  11. Lysimachia punctata 'Golden Alexander' Z3

  12. Monarda didyma 'Petite Wonder' Z3, Z3/4

  13. Oenothera acaulis

  14. O. x hybrida ‘Apricot Delight’

  15. Passiflora incarnata ‘Maypop’

  16. Persicaria amplexicaule 'Taurus' Z4

  17. Persicaria bistorta

  18. Phlox maculata ‘Franz Schubert’

  19. P. maculata 'Miss Karen'

  20. P. maculata ‘Natasha’

  21. P. maculata 'Shortwood'

  22. P. pilosa ‘Eco Happy Traveler’

  23. Polemonium caeruleum ‘Brise d’Anjou’

  24. Rosmarinus officinalis ‘Blue Lagoon’

  25. R. officinalis ‘Haifa’

  26. Rudbeckia sp. Z4

  27. R. x hybrida ‘Chim Ciminee’ Z3/4, Z3

  28. R. x hybrida ‘Greed Wizard’ Z3, Z4

  29. Salvia elegans ‘Pineapple’

  30. S. greggii 'Desert Blaze'

  31. S. pratensis (=haematodes) ‘Indigo’

  32. S. nemorosa ‘East Friesland’ Z3/4

  33. S. officinalis 'Nazareth' Z3

  34. Scabiosa columbaria ‘Butterfly Blue’ 2000 Perennial of the Year

  35. S. ocraleucra Z3/4, Z3

  36. Thymus variegata Z3

  37. Tiarella x hybrida 'Crow Feather'

  38. T. x hybrida 'Mint Chocolate'

  39. T. x hybrida 'Ninja'

  40. T. x hybrida 'Pink Brushes' Z3, Z3/4 (Morris), Z4 (St. Paul)

  41. T. x hybrida 'Pink Pearls' Z3, Z3/4, Z4 (St. Paul)

  42. T. x hybrida 'Tiger Stripe'

  43. Veronica x hybrida 'Blue Bouquet' Z4

  44. Vinca minor ‘Illumination’ Z3

Consult the following table to determine the performance of herbaceous perennials of interest to you. Data from 2007 will either further substantiate or modify the recommendations above.
Legend for Tables (Sources of Perennials).

AOP=American Ornamental Perennials

ATI=Anthony Tesselaar International

BB=Blooms of Bressingham

BlB=Blue Bird Nursery

BlN=Blooming Nursery

BN=Bailey Nursery

BP=Bluestone Perennials

BSC=Ball Seed Co.

FF=Flower Fields

GL=Green Leaf Enterprises

H=Heronswood Nursery

HC=Horticulture Club, University of Minnesota

NC=North Creek Nurseries

NG=Niche Gardens

PAS=PanAmerican Seed Co.

PPP=Pride of Place Plants

SG=Skagit Gardens

SN=Siskiyou Nursery

SO=Shady Oaks Nursery

T&M=Thompson & Morgan

TN=Terra Nova

UCT=University of Connecticut

U of M=University of Minnesota

VB=van Bourgondien

WFF=White Flower Farm

WG=Walters Garden

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