American Rose Annual 133-138 (1959)
Cold Hardiness of Rose Varieties
Dr. Griffith J. Buck*
Ames, Iowa

*Assistant professor of horticulture, Iowa State College.
Journal Paper No. J-3358 of the Iowa Agricultural and home Economics Experiment Station, Ames, Iowa. Project No, 1212. Presented at the American Rose Society's annual convention, May 29-31, 1958, Kansas City, Mo.

THE adaptation of plants to a given environment is of interest to all gardeners. The gardener in admittedly-difficult climatic areas is especially concerned with this problem, for it very effectively limits the kinds of plants which he can use in his garden. Two climatic factors (temperature and moisture) are involved in plant adaptation Of the two, temperature (especially sub-freezing temperature) is the principle limiting one,

The ability of woody plants (including roses) to withstand low Winter temperatures without injury is affected by several factors, including the ability of the tissues to retain moisture against freezing and store carbohydrates, drought (during which the plant evaporates fresh water faster than it can be replaced) and growth stimulation (clue to unseasonably-warm temperatures in mid-Winter). Plants which combine these factors at their highest positive values are the most resistant to low-temperature injury.

YOU CAN INCREASE RESISTANCE

By utilizing various cultural operations, the gardener may build up a plant's relative resistance to low-temperature injury, but he cannot increase this hardiness beyond the inherited maximum for that particular plant.

Observation of a plant's growth habits in a foreign environment, combined with knowledge of its native habitat, including the length of day (photoperiod), as well as temperature range, provides information which permits us to predict those broad climatic zones in which a given plant may be expected to flourish.

This is the type of information presented by Rehder,2 and more recently by Wyman.4,5 Rose growers, including Nicolas1 and Wright3, have attempted to provide the same type of information for the various garden rose groups and cultivated species.

This information is too general to be of much value to the home gardener. It deals with a broad range of plant material, whereas the gardener is concerned with asexually-maintained plant varieties (called clones).

EACH TYPE DIFFERS

There are many clonal selections among the species roses in cultivation. Each differs from the others in many traits, including that of hardiness, vet maintains a certain family resemblance. In general, those specimens coming from the more temperate portions of their habitat are less resistant to cold injury than those from the colder areas.

This inherent variability in resistance to low-temperature injury found in the species roses is also found in present-day garden roses. Within each rose class, individual clones have markedly-greater hardiness than the average for the group. Others are less resistant. The most casual gardener may observe this for himself. And yet, over a period of years, it has been possible to determine the average winter-hardiness of a given rose clone and to classify those clones into groups having a similar degree of resistance to freeze-injury of mature, well-ripened wood. There is still some variability within the groups, although these differences tend to be small.

Occasionally, an unusual weather occurrence aids in segregating the more-resistant members of each group from the less-resistant. Such an event occurred during the Winter of 1956-57. On the night of January 14, 1957, the temperature dropped to -30° F., then with daylight, rose to -19°F. The average minimum temperature for the period of January 12-20 was 10° F.

Compared with this average minimum temperature, the actual minimum temperatures for the period were as follows:

Jan. 12 40°F. Jan. 16 -14°F.
" 13 - 7°F. " 17 - 2°F.
" 14 -30°F. " 18 3°F.
" 15 - 4°F. " 19 5°F.

 A 15-20° departure from the average in either direction is not unusual. The lowest minimum temperature normally expected in this vicinity is -25°F. However, this temperature does not occur every Winter. The rest of this particular Winter, both preceding and following January 14, has been characterized as a "normal" one.

What makes this event of interest is that it occurred during the night, with no appreciable air movement and with the soil bare of snow cover. Thus, such modifying effects as sunshine on frozen canes, wind dessication and the insulation effect of snow cover were absent. Coming as it did in mid-January, there had been no warm periods to incite premature growth and thus increase the plant's susceptibility to winter-injury.

NOW WE CAN TELL

This combination of circumstances made it possible to assess the resistance of a number of rose clones to injury from temperatures lower than those normally expected here when pruning time arrived in mid-April. The following five classes of hardiness were observed:

Class 1. No winter-killing of mature wood; plant resumes normal growth and flower habit with growing temperatures.

Altalaris (Shrub) Rosa beggeriana
Aines 5 (Climber) Rosa fedtschenkoana
Ames 6 (pillar) Rosa laxa (Morden)
Berry Bland (Shrub) Rosa laxa (Fall-blooming form)
Felicity (Shrub) Rosa morica
flaidee (Shrub) Rosa spinosissima altaica
Hansen's Siberian Hedge Rose (Rosa laxa sp.) Suzanne (Shrub)
Hanson's Profuse (Shrub) Therese Bugnet (Shrub)
Little Betty (Shrub) Victory Year (Shrub)
Mossman (Moss) Will Alderman (Shrub)
Pink Semi (Rosa laxa rosea?) Woodrow (Shrub)

 Class 2. One-third or less of each cane killed.

Agnes (Shrub)† Pax Apollo (Sbrub)†
Belle Amour (Shrub) Pikes Peak (Shrub)†
Belle des Jardins (Gallica) Pink Glory (Shrub)†
Blanchefleur (Gallica) Prairie Youth (Shrub)†
Blanche Moreau (Moss) River's George IV (Hybrid China)
Blush Hip (Rosa alba sp.)† Rosa alba incarnata maxima†
Carmenetta (Shrub) Rosa alba suaveloens†
Charles de Mills (Gallica)† Rosa canina (Senff)
Comtesse de Murinais (Moss) Rosa canina (Wadenswiler)
Desiree Parmentier (Gallica) Rosa corymbifera†
Dr. E. M. Mills (Shrub) Rosa gallica†
Frau Dagmar Hartopp (Hybrid Rugosa) Rosa gallica complicata
Fruhlingsanfang (Shrub) Rasa gallica conditorum
Fruhlingsduft (Shrub) Rosa multiflora (Clarke)
Hansette (Shruh)† Rosa multiflora (Welch)
Hebe's Lip (Shrub) Rosa nutkana halliana
Karl Forster (Shrub) Rosa pomifera
La Belle Distinguée (Hybrid Eglanteria)† Rosa rugosa alba
Lillian Gibson (Shrub)† Rosa rugosa magnifica†
Maiden's Blush (Alba)† Rosa virginiana†
Marie Louise (Damask)† Rose du Maitre d'Ecole (Gallica)†
Mary L. Evans (Shrub)† Salet (Moss)†
Mrs. Anthony Waterer (Shrub) Sonnenlicht (Shrub)†
Nuits d'Young (Moss)† Variegata di Bologna (Bourbon)

Class 3. More than one-third, and less than two-thirds of each cane killed.

Assemblage des Beautes (Gallica) Mme. Hardy (Damask)†
Bonn (Hybrid Musk) Mme. Louis Leveque (Moss)
Celestial (Shrub)† Petite de Hollande (Centifolia)
Celsiana (Damask) Prairie Moon (Large-flowered Rambler)
Coquette des Alpes (Noisette) † Prince Charlie (Hybrid Tea)
Coquette des Blanches (Noisette)† Rosa alba maxima
Cramoise des Alpes (Gallica) Rosa canina (Gamon)
Elnsshorn (Hybrid Musk) Rosa canina (Heinsohn)
Empress Josephine (Shrub) Rosa canina (Pfander)
Eugenie Guinoisseau (Moss)† Rosa canina (Pollmeriana)
Eureka (Hybrid Tea)† Rosa damascena semperflorens
Fruhlingsmorgen (Shrub)† Rosa multibracteata
Golden Moss (Moss) Rosa noisettiana manetti
Gros Provins Panache (Gallica) Rose due Roi (Damask)†
Indian Head Cabbage (Centifolia) Sophie de Baviere (Rosa alba sp.)
James Mitchell (Moss) Stasswell Perpetual (Shrub)†
Konigin von Danemark (Mba) St. Nicholas (Damask)†
Leda (Tea)† The Bishop (Hybrid Tea)
Marigold (Hybrid Tea) Tom Money (Large-flowered Rambler) †
Master David (Hybrid Tea)† Unique Panachee (Centifolia)
Maytime†  

 Class 4. All canes killed to within 6-12" of plant base.

Adam Messerich (Bourbon) La Perle
Aglaia (Rambler) Alfred de Dalmas (Moss) LaVille de Bruxelles (Damask)
Allen's Fragrant Pillar (Climbing  Hybrid Tea) Lawrence Johnston
Aloha (Climbing Hybrid Tea) Leverkusan (Kordesii)
Aschermittwoch (Large-flowered Climber) Lullaby (Floribunda)*
Autumn Bouquet (Shrub)† Master John (Climbing Hybrid Tea) *
Baronne Prevost (Hybrid Perpetual)* Max Graf (Hybrid Rugosa)
Black Prince (Hybrid Perpetual)* Miss Joan (Climbing Hybrid Tea)
Buff Beauty (Hybrid Mask)* Miss Marion Manifold (Climbing Hybrid Tea)
Celine Forestier (Noisette)* Mme. Ernest Calvat (Bourbon)†
Chions (Rosa alba sp.) * Mine. Pierre Oger (Bourbon)
Commandant Beaurepaire (Bourbon) * Nevada (Shrub)*
D'Aguesseau (Callica) Nymphenburg (Shrub)†*
Danae (Hybrid Musk)* Oskar Cordel (Hybrid Tea)*
Daphne (Hybrid Musk) * Parkjewel (Shrub)*
Dcicanso Pillar (Shrub)* Patricia Macoust (Rambler)
Deuil de Paul Fontaine (Moss)* Paul's Scarlet Climber (Large-flowered Rambler) †
Dr. Huey (Rambler) Pax (Hybrid Musk) *
Duchesse de Montebello Gallica) Pompon Parfait (Alba)
Duchess of Sutherland (Hybrid Perpetual) President de Seze (Gallica)
Duke of Edinburgh (Hybrid Perpetual) * Prosperity (Hybrid Musk)
Etaine (Rambler) Rosa centifolia  bullata
Felicite et Perpetue (Rambler) Rosa centifolia cristata
Felicite Parmentier (Alba) Rosa helenae florepleno
Flammentnnz (Rambler) Rosa moyesii superba*
Fruhlingschnee (Shrub) Rosa multiflora grandiflora
Fruhlingstag (Shrub) Rosendorf Ufhoven (Shrub)
Gabriel Noyelle (Moss)* Skyrocket (Hybrid Musk)*
General Jacqueminot (Hybrid Perpetual) Souvenir d'Alphonse Lavalle (Shrub)
Gloire de Guilan (Damask)† Sparrieshoop (Shrub)†
Gloire des Mosseaux (Moss) Thisbe (Hybrid Musk)
Goldbusch (Shrub) Tour de Malakoff (Centifolia)
Golden Wings (Hybrid Tea) Triomphe de l'Exposition (Hybrid Perpetual)*
Henry Nevard (Hybrid Perpetual)* Tuscany (Grandiflora)
Hon. Lady Lindsay (Shrub)* Victor Hugo (Hybrid Perpetual)
Josef Rothmund (Shrub) Will Scarlet (Hybrid Musk) *
Lady Carson (Shrub) Zweibrucken (Kordesii)

Class 5. Plants completely killed.

Antoine Rivoire (Hybrid Tea)* Lowell Thomas (Hybrid Tea)†*
Bloodstone (Hybrid Tea.)* Lucia Zuloaga (Hybrid Tea)†*
Border Queen (Floribunda)†* Madcap (Floribunda)†*
Bridal Veil (Floribunda)†* Misty Gold (Floribunda)"
California (Hybrid Tea)* Molly Bishop (Hybrid Tea)*
Charles Mallerin (Hybrid Tea)* Mrs. Edward Laxton (Hybrid Tea)*
Courtship (Hybrid Tea)†* Mrs. John Laing (Hybrid Perpetual) †*
Coy Colleen (Hybrid Tea)†* Mrs. Sam McGredy (Hybrid Tea) †*
Girona (Hybrid Tea) * Narsisse (Hybrid Tea) *
Golden Glow (Hybrid Tea)* Nuria de Recolons (Hybrid Tea) †*
Golden Revelry (Hybrid Tea)†* Poinsettia (Hybrid Tea)†*
Heinrich Munch (Hybrid Tea)†* Rosa highdowensis
Ida McCracken (Hybrid Tea)* Rosa moyesii
Jackman's White (Hybrid Tea)* Rosa pruhoniciana
Jaune Deprez (Moss)* Souvenir de Georges Pernet (Hybrid Tea)*
Karen Poulsen (Floribunda)* Tzigane (Hybrid Tea) *
Le Vesuve (China)* Ulster Monarch (Hybrid Tea)*
Lorraine Lee (Hybrid Tea)* Virgo (Hybrid Tea)†*
Louisiana Purchase (Hybrid Tea)†*  

Plants would, in normal Winters, be included in next-hardier class (applies to Hybrid Teas, Floribundas and Grandifloras in general).
* Received winter protection in the form of a 10" cone of soil around the base of the plant.

Classifications indicated according to Modern Roses V.

  1. Nicolas, J. H. Arcticness and Mathematics. American Rose Annual 22:166-169 (1937).
  2. Rehder, Alfred. Manual of Cultivated Trees and Shrubs, 2nd Edition, 1947.
  3. Wright, Percy H. The Arcticness of Various Roses. American Rose Annual 23:71-74 (1938).
  4. Wyman, Donald. Shrubs and Vines for American Gardens (1953).