American Rose Annual pp. 57-71 (1957)
Breeding Winter-Hardy Rambler Roses
Edward Baker Risley

Abstract

Professor Risley is an assistant professor of horticulture at the University of New Hampshire, Durham, The story is extracted from his master's thesis. By supplying the framework of a major breeding project, it is felt that amateurs interested in breeding will see the value of organization in breeding work and may thus put their own programs on a sounder basis.

This is a record and discussion of the progress made between 1950 and early spring of 1955 on the development of a rambler rose of acceptable quality and hardiness sufficient to permit wintering over of the canes without protection in the northern half of New England and similar areas.

Two means were adopted to rate the hardiness needed and a survey was made of the available hardy roses that might be used to develop such a rambler. Skinner's Rambler, a seedling of Rosa Maximowicziana, made available by Dr. F. P. Skinner of Manitoba, Canada, was hybridized with a large number of other roses to produce many seedlings.

The specialized plant breeding techniques used and an original three-step system for recording taxonomic data developed to fit the needs of this project are described.

Eleven selected, numbered seedlings and the nine progenies of which they were a part are discussed in detail. Twenty-two additional groups of seedlings and the F2 generations of some of the numbered seedlings are briefly evaluated. Included are discussions of the breeding behavior of roses in general and R. caninae sp. in particular.

Objective

A rambler rose having desirable qualities including winter hardiness sufficient to permit survival of the canes without protection throughout all of the northeastern United States is an objective of one portion of the New Hampshire Agricultural Experiment Station project entitled "Improvement of Ornamental Plants." Some of the desirable qualities sought, besides the essential winter hardiness, are vigorous growth, foliar disease resistance, beautiful and fragrant flowers in large cymes, extended flowering season, glossy dark green leaves having Sweet Brier Rose fragrance, and large, attractive and useful fruits.

Reasons

Roses classified commonly in the nursery trade as Large Flowered Climbers, Old Fashioned Ramblers, Everblooming Pillars, and Climbing Hybrid Teas, and herein referred to simply as ramblers, do require an unreasonable amount of care to protect the canes from winter injury in New Hampshire and similar northern areas.

The temperature -15°F. may be taken as the critical point below which the canes of all rambler roses offered in current nursery catalogs will be killed. It may be concluded that the four southern counties, Strafford, Rockingham, Hillsboro, and Cheshire, where 60% of the state's population lives, may expect -15°F. at some time during 20% to 100% of the winters, depending on the exact location of their homes within the area. Plants growing in Sullivan, Merrimack, and the four northern counties will normally be subjected to -15°F. during 50% to 100% of our winters. The only parts of New Hampshire in which rambler roses appear never to get frozen back are the coastal portions of the cities of Portsmouth and Newcastle where large specimens have developed.

New Hampshire people buy rambler roses from western and southern nurseries every year with or without an understanding of the possibility of losing them in a few years' time from winter injury. There would unquestionably be a northern market for a good rambler that could withstand -20°F. to -30°F. without protection. With available hardy rose species and varieties it is reasonable to assume that such a rose may be developed by modern plant breeding methods.

Previous Work

Little effort has been made to develop rose varieties specifically for the northeastern United States where winter temperatures below -15° F. occur commonly. The rose breeding that has been done for the people of the north has been the work of a few amateurs like Georges Bugnet and dedicated nurserymen like Frank Skinner and Percy Wright, all three of whom live in the colder parts of Canada. In Iowa, Professors T. J. Maney and G. J. Buck have been developing hardy ramblers and hardy rootstocks for roses in the central west where conditions of climate and soil make it desirable to develop varieties inherently suited to that region. Little has been done to develop roses for the northeastern coastal and mountain areas where a combination of low minimum temperatures and wet soils in winter makes rose culture difficult. In the mild, humid coastal areas of Massachusetts, Rhode Island, and Martha's Vineyard, the rambler roses developed from Rosa Wichuraiana and R. multiflora by Horvath, Walch, Dawson and others early in the twentieth century are at their best. These are not reliably hardy inland and to the north and lack many of the desirable qualities possible.

Procedure
Roses Collected and Sources of Plants

Between 1950 and 1954 a collection was made at the University of New Hampshire Horticulture Farm of modern and old-fashion roses and Rosa species of widely varying sorts. These were grown both for observation and for testing the probable breeding value of each kind. Each variety was carefully selected because it was alleged to be the best available having the qualities that are needed in this project.

The following roses were used as parents in the summer of 1952:

  ROSE SOURCE OF PLANTS
1. Betty Bland Skinner's Nursery, Manitoba, Canada.
2. Rosa Wichuraiana Bobbink & Atkins New Jersey.

In addition to these two, the following were also used in the summer of 1952:

3. Chamcook 9. Pinocchio
4. Chevy Chase 10. Rosa pomifera
5. Hon. Lady Lindsay 11. Rosa rubrfolia
6. Mabelle Stearns 12. Rosa virginiana
7. Oratam 13. Skinner's Rambler
8. Paul Neyron    

In addition to those used in 1950 and 1952 the following varieties which had been added to the garden were used as parents in the summer of 1953 with the exception of those noted as growing elsewhere from which pollen was secured:

14. Belinda 27. Minnehaha
15. Charlotte Armstrong 28. New Dawn
16. Dream Girl 29. Pink Grootendorst
17. Evergreen Gem 30. Poulsen's Bedder
18. Flora Mclvor 31. Queen of the Lakes
19. Fragrant Beauty 32. Rosa eglanteria
20. Golden Rapture 33. Rosa nitidia?
21. Green Mantle 34. The Fairy
22. Gruss an Aachen 35. Thérèse Bugnet
23. Harison's Yellow 36. V for Victory
24. Henri Martin 37. Vogue
25. Lafter 38. Yvonne Rabier
26. Ma Perkins 39. #500

 In the summer of 1954 emphasis was placed on obtaining seeds for an F2 generation from the most promising rambler seedlings of the 1952 pollinations in this project. Those numbered seedlings of Skinner's Rambler which were used for further breeding in 1954 are:

NUMBER PARENTAGE
#520 Skinner's Rambler X Rosa pomifera
#524 Skinner's Rambler X Betty Bland
#527 Skinner's Rambler X Pinocchio
#5211 Skinner's Rambler X Skinner's Rambler
#5214 Chevy Chase X Skinner's Rambler
#5217 Skinner's Rambler X Skinner's Rambler

 In addition the following roses were used in 1954 largely as pollen parents on either Skinner's Rambler or on selected 1952 seedlings of Skinner's Rambler:

40. Bonfire 46. Orange Ruffels
41. Brownell Everblooming
Pillar #84 (pink)
47. Persian Yellow
42. Diamond Jubilee 48. Professeur Emile Perrot
43. Lady Penzance 49. Tawny Gold
44. Lord Penzance 50. Yellow Pinocchio
45. Mandalay    

Three seedling plants of Rosa Roxburghii were shipped from the Arnold Arboretum, Jamaica Plain, Mass., by Dr. Donald Wyman in the spring of 1952 and were planted at the U. N. H. Horticulture Farm with the expectation of using this species extensively in this project. The plants have grown into vigorous and beautiful five-foot bushes but have not flowered.

Grouping of Roses Used According to Purpose

The following lists indicate which of the roses used in this project, according to the literature and previous personal experience, might reasonably be expected to contribute each of the desired qualities in a seedling rambler rose. The outstanding ones in each category are preceded by an asterisk*:

1. WINTER HARDINESS OF CANES:
    *Betty Bland Rosa pomifera
    Chamcook *Rosa rubrifolia
    Hanson's Yellow Rosa virginiana
    Pink Grootendorst *Skinner's Rambler
    Rosa nitida Thérèse Bugnet
2. LONG CANES (RAMBLER):
    Bonfire Max Graf
    Brownell Ev. Pillar #84 Minnehaha
    Chevy Chase New Dawn
    Dream Girl *Rosa Wichuraiana
    *Evergreen Gem *Skinner's Rambler
3. LONG FLOWERING SEASON (EVERBLOOMING):
    Belinda *Orange Ruffels
    Brownell Everblooming P. #84 *Pink Grootendorst
    *Diamond Jubilee *Pinocchio
    Fragrant Beauty Poulsen's Bedder
    Green Mantle Queen of the Lakes
    *Gruss an Aachen *Tawny Gold
    Hon. Lady Lindsay *The Fairy
    *Lafter Thérèse Bugnet
    Mabelle Stearns Vogue
    *Mandalay *Yellow Pinocchio
    Ma Perkins *Yvonne Rabier
    New Dawn  
4. FOLIAR DISEASE RESISTANCE:
    Blackspot Resistance Mildew Resistance
    Evergreen Gem * Chevy Chase
    Henri Martin Max Graf
    *Lafter Rosa eglanteria
    *Max Graf Rosa Roxburghii
    Minnehaha *The Fairy
    Rosa Roxburghii  
    Rosa Wichuraiana  
    The Fairy  
    Yvonne Rabier  
5. BEAUTIFUL FLOWERS:
  a. Number of petals:
    All species listed above have five petals.
    All horticultural varieties except Skinner's Rambler have many
petals and Skinner's Rambler is heterozygous for many petals.
  b. Flowers in large cymes:
    *Belinda Rosa Wichuraiana
    Bonfire Skinner's Rambler
    Minnehaha *The Fairy
    Pink Grootendorst  
  c. Outstanding color:  
    Bonfire Mandalay
    Chevy Chase Minnehaha
    Diamond Jubilee Orange Ruffels
    Dream Girl Oratam
    Golden Rapture Queen of the Lakes
    Green Mantle Tawny Gold
    Henri Martin Yellow Pinocchio
    Lafter  
  d. Attractive petal form:
    *All the Hybrid Teas and Floribundas listed previously.
    Evergreen Gem Oratam
    Honorable Lady Lindsay Pink Grootendorst (Serrated)
  e. Mossed calyx (Moss Rose):  
    7 varieties of Moss Roses not listed above and Henri Martin.
  f. Fragrance:  
    Most of the Hybrid Teas and Floribundas.
    *Oratam and *Prof. Emile Parrot (Damask or perfume roses) —
see also fragrant leaves below
6. THORNS:
  a. Attractive thorns:  
    *Green Mantle *Rosa Roxburghii
  b. No thorns or few thorns:  
    *Betty Bland Thérèse Bugnet
    Bonfire *#524 seedling
7. ATTRACTIVE LEAVES:
  a. Surface texture  
    Rugose Smooth and waxy
    *Max Graf *Chevy Chase (leathery)
    Oratam *Evergreen Gem
    *Pink Grootendorst *Lafter
      *Rosa Wichuraiana
    Velvet (hirsute) *#527 seedling
    *Rosa pomifera Yvonne Rabier
  b. Leaf color  
    Rich dark green Red
    Evergreen Gem Rosa nitida *Rosa rubrifolia
    *Green Mantle Rosa Wichuraiana
    Henri Martin The Fairy
    Lafter Yvonne Rabier
    *Oratam *#527 seedling
  c. Persistence on the plant until late fall:
    *Evergreen Gem Rosa Roxburghii
    Henri Martin Rosa virginiana
    *Max Graf Rosa Wichuraiana
    Rosa eglanteria *The Fairy
    Rosa nitida *#527 seedling
  d. Fragrant leaves:
    * Rosa eglanteria and its seedlings such as —
    * Green Mantle Flora Mclvor
    Lady Penzance Lord Penzance
8. ATTRACTIVE FRUITS:
    Chamcook Rosa Roxburghii
    *Rosa eglanteria *Rosa rubrifolia
    *Rosa nitida Rosa virginiana
    *Rosa pomifera Skinner's Rambler

Recording Taxonomic Data

A procedure was sought for recording the exact nature of each plant used which would define accurately for everyone interested just what the plant looked like and how it behaved. Pursuit of this procedure involved three steps. First the morphological and known ecological and genetic characteristics were recorded on mimeographed taxonomic data sheets which were developed specially for this project in cooperation with D. A. R. Hodgdon.18 These sheets are similar in content to but more complete than the standard registration forms of the American Rose Society for naming and recording new rose cultivars at the time of distribution. These taxonomic data sheets provide a rapid, definitive, and uniform means of recording data in the field or from herbarium specimens.

A second step in recording rose parents and their seedlings was to assemble representative plant parts under a specially designed camera frame and record their gross appearance photographically. The primary value of this procedure was to have a visual description of the plants for publication. The close-up views of leaves, flowers, stems thorns, and fruits in this thesis were taken with a Bolsey B-2 (35mm) camera using a 3 diopter Kodak Porta Lens and Kodak Plus-X film. The camera was mounted on a frame made of wood and 1/4" iron rod which was designed and built by the author from suggested plans in a booklet issued by the Eastman Kodak Company. This inexpensive frame, which may be used out in the field in natural sunlight, or indoors with attached floodlamps, enables the busy plant breeder to get a close-up record of his plants quickly, surely, and in any kind of weather. Exposure time was found to be 1/200 second at an aperture of f16 outdoors in summer sunlight, and 1/50 second for most subjects taken indoors. The frame assured that plant parts 12" away were in focus and just filled the negative. Thus it was not necessary to use an expensive ground glass focusing camera for this work. Photography has the advantage of recording taxonomic data without destruction of plants or flowers which may be valuable for breeding purposes at the time, and the prints are less bulky to store and less fragile than herbarium specimens. In the case of seedling rambler roses, however, there are always ample flowering and vegetative plant parts for breeding, pressed specimens and photographs.

The third procedure for permanently recording the exact nature of the plants used in this project was to make pressed herbarium specimens of the parent plants and any seedlings worthy of distribution or use in further breeding. It was the author's practice to collect at flowering time a complete inflorescence attached to a section of mature wood if the total was not too large to fit on a single sheet of standard herbarium paper. In addition, a representative mid-section leaf with stipules, a flower cut in half to show orientation and numbers of reproductive parts, and a complete ring of sepals were collected at that time. In the fall a second collection was made from the same plant to get mature hips and a section of mature cane to show bark color and prickles. Parts from this fall collection were mounted on the same herbarium sheet with the flowering parts to give a complete picture of the plant on one sheet. These horticultural herbarium specimens have the advantage of longer life under proper storage conditions than photographic prints and the more important advantage of permitting microscopic examination of any of the plant parts at any time.

Pollen Collection and Storage

It would not have been possible to interbreed many of the roses in this diversified collection without some means of storing pollen because of the wide differences that exist in date of bloom. Anthesis of Rosa pomifera started on June 7 but R. Wichuraiana did not begin to bloom until June 30. R. pomifera completed anthesis by June 15. Thus a minimum storage period of fifteen days was required for the pollen to be used for the pollination of R. Wichuraiana. Literature on pollen storage in general indicates that pollen remains viable longest if stored in a moderately dry and cool atmosphere, 45% relative humidity and 31°F. being best for R. setigera.20

Pollen was collected from flower buds one day prior to anthesis to assure no contamination with foreign pollen which might be brought in by visiting insects. Flowers to be used as a source of pollen were removed from the plants in most cases unless the scarcity of flowers demanded that the same flower be emasculated and also be used for hand pollination. While holding the receptacle of a flower in one hand and using a pair of curved tip, sharp-pointed, surgical tweezers in the other, the sepals and petals were removed. Next, the ring of filaments was removed and the excised anthers were dropped onto clean sheets of glazed paper and set aside for dehiscence. The anthers and pollen were dried for 24 hours at room temperature. The pollen was then slid off the paper into waxed milk bottle covers, each labeled as to variety. To conserve valuable time for emasculation and pollination in the field during daylight hours, all processing of pollen took place late in the evening. This greatly increased the number of crosses that could be made in one season by one worker.

Three milk bottle covers, it was found, would fit into a cylindrical, 3 1/2" transparent, cheese box having a tight fitting cover. A layer of calcium chloride was spread over the bottom of each box to aid in maintaining a low humidity. The boxes were easily stacked in a home refrigerator whose temperature was maintained at about 40 °F. The pollen boxes made daily trips to the rose garden in a small portable picnic ice box. Whether there was any loss of viability in the pollen during the four-week pollination period is not known because no germination tests on artificial media were made. Nevertheless pollinations made in early July, using pollen from the same container of stored pollen as had been used in early June, produced many seeds. A camel hair brush was used to transfer pollen from the milk bottle covers to the stigmas of flowers emasculated one to two days earlier.7 It was noted that some of the pollen stuck to the wax on the bottle covers and in cases where little pollen was available, this further reduced the usable pollen. Dr. Yeager suggested the use of small shell glass vials that would concentrate all the pollen in a small area where the brush could get at it. A small tin can with a tight fitting cover and a layer of calcium chloride in the bottom held a cluster of these vials of pollen, each vial having been labeled in pencil on a strip of adhesive tape.

Pollination

Preparation of the flowers for hand pollination began with emasculation one day before anthesis. To prevent contamination of the emasculated flowers with unwanted pollen, a one-pound kraft paper bag was placed over each flower or flower cluster and was attached with a short length of paper covered wire. The date of emasculation was noted on the bag in pencil. This served as a guide for pollination which was done one or two days later. In the case of a cluster type of inflorescence, the date was a reminder to open the bag not less than once in 48 hours to emasculate new flowers before they could shed pollen. In hot weather immediately following a cool rainy period, daily inspection of the bags was necessary to prevent sell pollination. Skinner's Rambler and its self pollinated seedlings normally opened two to six flowers per day in each cyme of 10 to 40 flowers, and stigmatic fluid indicating receptivity appeared the first day following emasculation in hot weather and on the second day in cool weather. Flowers opened more slowly and appeared receptive over a longer period in the case of the double flowered, cluster type ramblers such as Bonfire, Belinda and Chevy Chase. The native R. cinnamomeae sp. have dry but hairy stigmas which are apparently receptive to pollen of their own group but not to any from outside the group. The kraft paper bags offered good protection from the rain except during infrequent torrential downpours when the saturated bags broke the entire inflorescence downward. Loss of some hips on Skinner's Rambler was noted as being due to the presence of mildew disease on the receptacle or on the pedicel, and the flowers showing this condition at pollination time rarely developed good hips or seeds.

Individual flowers or whole clusters were labeled as to the cross made, always including both parents to prevent confusion after collection from the field. Collection usually took place in a rush on a cold afternoon preceding an anticipated early fall freeze. Tags of white paper, 2 1/4 x 1 7/8 inches, with string attached were found satisfactory under all weather conditions, including two hurricanes in 1954.

Pollination proceeded on the assumption that all desired combinations should be tried and tried repeatedly whether or not sterilities and differences in chromosome number and behavior existed. It was felt that progress might best be measured in terms of valued new combinations produced rather than total number of conventional type seedlings produced. The crosses attempted and their degree of success are discussed in the thesis proper. Persistence was felt to be both essential and rewarding when making "wide" crosses in the genus Rosa where one finds a long history of excellent rose varieties arising from slightly fertile triploids36 and unbalanced chromosomal types bearing desired genes.

Seed Stratification and Germination

Seeds were removed from the hips early in the fall as soon as the ripe fruit color began to appear and were stratified immediately without drying as recommended by Horvath31 to prevent a long dormancy in the seeds. The length of the dormant period in different rose seeds varies widely from a few weeks to seven years. That stratification at 38°F. to 41°F. for a period of 60 to 120 or more days is necessary for the germination of most rose seeds was noted in the literature.9

The 1950, 1952, and 1953 seeds were stratified in shell vials filled with shredded sphagnum moss31 and plugged with a wad of sterile cotton. The moss was soaked and wrung out to remove excess water before going into the vials. The cotton soon molded, the moss dried out excessively, and many germinated seedlings were broken in trying to remove them from the vials. In 1954 all rose seeds were stratified immediately following early collection using moist shredded sphagnum moss in four-inch petri dishes. (I am now using polyetheline bags instead.) Water loss was reduced and the seedlings were easily removed without breakage. In 1953 "Arasan" was used to disinfect the seeds. No disinfectants were used in 1954 on the moss or the seeds. Quite a few of the seedlings were lost both years soon after germination from shriveling and browning of the roots. It has not been determined whether this was due to a fungus disease or to lack of water in the moss which is known to have a strong affinity for water. It has been observed often that the healthiest seedlings, in terms of percent survival, were those taken from the petri dishes in which the moss was exceptionally moist. Those seedlings having a firm white root with many root hairs almost always survived after potting. Mold growth often prevented saving the seeds for more than one year, yet Dr. Van Fleet recommended keeping them as long as 7 years to allow all possible seeds to germinate.31 The author's philosophy is to discard all ungerminated seeds at the end of the first year to insure the perpetuation only of those roses having genes for rapid germination. This recognizes the danger that valuable genes linked closely with slow germination may be lost by this action.

The vials or petri dishes were inspected once each week after December 1 to remove all the seedlings that had germinated before they had become excessively elongated. The tiny seedlings were put into soil in two and a half inch clay pots individually labeled to prevent error in later identification. These pots were subirrigated and plunged to their rims in sand, sawdust, or soil in benches under lights that were controlled to lengthen each day to 14 hours or longer. The thermostats controlling air temperature in the greenhouse were set at 55°F. at night in 1951, 1953, and 1954, and 50 °F. in 1955.

Care of the Seedlings

Late in the spring, growth of the seedlings was rapid and several transplantings into larger pots were required. Most of the seedlings required four or five inch pots and supplemental feedings of liquid 20-20-20 fertilizer to prevent hardening of top growth and root binding. Hardening was avoided to prevent possible termination of active growth for the season, which, in turn, might delay flowering one year. These potted plants were moved to the field from the greenhouse at various dates after the weather had warmed and frosts were no longer a danger to the plants.

It was necessary to plan to provide a trellis support for all of these seedlings because each had a rambler or long caned rose as one of its parents and long canes are dominant.30 Supports four feet high were necessary the first year and the canes often grew to 15 or more feet the second year. Cedar posts eight feet tall, one for each four plants, with #18 galvanized wire strung between were used in this project and the canes were attached to the wires with short lengths of paper covered wire. This support, fully covered with canes, withstood the two hurricanes of 1954 which blew down apple trees a short distance away.

Field care of the plants consisted of clean cultivation or manure mulch, irrigation when it seemed necessary to prevent hardening of growth, and periodic attachment of the rapidly growing canes to the wires and spraying several times with a mixture of lindane, Aramite, captan, malachite green and a spreader-sticker. The spray was to control severe attacks of insects, mites, mildew and blackspot but was not used too frequently so that adequate records could be taken indicating relative susceptibility of both the parents and seedlings to these two diseases. The seedlings not having moderately high resistance to foliar diseases were destroyed. No disease susceptible rose was used for breeding purposes unless the genes it possessed for some other valuable quality were not readily available from a disease resistant rose.

Labeling

Field labeling of large numbers of individual plants was found to be time consuming but unavoidable if meaningful records were to be kept. A code was used to speed the labeling. As an example all seedlings of the cross Skinner's Rambler (female) x Rosa virginiana (male) made in the summer of 1952, were simply identified on the labels as "SR2V." When planting had been completed for the season, a map listing the position of each plant in the field was made. Accidental destruction of labels often proved the value of such a map. Those few outstanding individual seedlings selected from the many in the field for further observation, breeding a second generation, or possible introduction were given a number such as 520, 521, 522, etc., if they originated from 1952 seeds, or 530, 531, etc., if from 1953 seeds. The complete taxonomic description of each of these numbered selections was recorded on one of the taxonomic data sheets, photographs of several were taken, and pressed specimens will later be made of any that prove worthy of introduction.

Determination of Winter Hardiness

Two criteria were used to determine relative winter hardiness in roses. The more useful criterion of the two was a record of the living portion of the plant remaining in June as compared with other roses growing in the same garden whose hardiness is well known. Table 2 lists the relative winter hardiness of 114 rambler seedlings and their parents in the winter of 1953-1954. It was easily constructed by recording the percent of the top of each plant alive at the beginning of spring.

A second method of rating the winter hardiness of roses is to determine the lowest winter temperature at which each kind will survive by field observation over the years. Because minimum winter temperature is but one of the many factors involved in winter survival, this criterion is perhaps best used only as a general indication of the geographical areas in which it is reasonable to expect survival. As a general guide the following was found in the literature:

Minimum
Temperature
Rose and Reference
-15°F Rosa Wichuraiana (7, p. 89) (27, p. 187)
  Gallicas, Austrian Copper, Scotch Roses, and some Polyanthas (27, p. 168)
-20°F Rosa multiflora (34, p. 73)
  Centifolias, Mosses, Damasks, Austrian Briars (27, p. 168)
-30°F Rosa multiflora, R. rugosa, some CANINAE, few Spinosissimas, native roses (27, p. 167) (34, p. 74)
-40°F Rosa rubrifolia, Persian Yellow and Harison's Yellow R. xanthina, R. foetida, R. cinnamomea (34, p. 74)
-50°F Rosa blanda, Ross Rambler, R. Beggeriana (34, p. 74)
-60°F Rosa acicularis (34, p. 74)

Differences of opinion are shown in this listing. Rosa multiflora, for example, is the subject of much controversy as to its hardiness. Hardy races of this rose may exist unlabeled as such but it is more probable that the differences are due to other factors affecting hardiness locally. It may best be rated as normally hardy only in protected locations in the warmer half of New Hampshire.1

(Mr. Risley then describes many of the crosses made and evaluates the resulting seedlings. Several of these give promise of value in the future breeding but probably none of them will be introduced as one would expect this early in a long range program.)

TABLE 2
Winter hardiness (1953-1954) of 114 rambler rose seedlings and their parent plants.
U.N.H. Horticulture Farm, Durham. N. H.
Minimum temperature approximately -14°F., 1/14/54.

Number of plants in the garden
SEEDLINGS *A B C D
Chevy Chase X Skinner's Rambler   2 2  
Paul Neyron X Skinner's Rambler   2 2 3
Rosa Wichuraiana X Betty Bland 1   12  
Skinner's Rambler X self 8 2    
Skinner's Rambler X Betty Bland 2      
Skinner's Rambler X Oratam 7 28 5  
Skinner's Rambler X Paul Neyron   4 14 8
Skinner's Rambler X Pinocchio 2 4 1  
Skinner's Rambler X R. pomifera   1 2  
Skinner's Rambler X R. rubrifolia     1 1
PARENTS        
Betty Bland 9      
Chevy Chase     2  
Oratam   1    
Paul Neyron       1
Pinocchio     1  
R. pomifera 2      
R. rubrifolia 2      
R. Wichuraiana     6  
Skinner's Rambler 5      
*A, no injury to canes or buds.
B, top hall of canes killed, lower half alive.
C, all canes frozen to the soil level, roots alive.
D, dead, entire plant killed.

Sample Taxonomic Sheet
SPECIES: Rosa hybrida Hort.
VARIATIONS: Skinner's Rambler (F. L. Skinner, 1953)