Rose Alaska

'Alaska' is a modern white Climbing rose with unusually full, rosette shaped flowers, compact climbing growth, abundant foliage, and notably strong garden health. It combines the romantic appearance of an old fashioned, full white rose with the recurrent flowering and disease resistance expected of a modern Kordes climber. The flowers are essentially white, sometimes carrying a faint cool pink or red-purple tint on the outermost petals, and are borne both singly and in small clusters against substantial leathery foliage. Its moderate ultimate size makes it particularly useful where a full-scale rambler would be excessive: arches, pillars, trellis panels, fences and comparatively small house walls are all appropriate. For gardeners seeking a white climber that is floriferous without becoming overwhelmingly large, 'Alaska' is one of the more interesting introductions of the twenty-first-century Kordes breeding programme.

DESCRIPTION OF THE VARIETY

Rose 'Alaska' horticulturally behaves as a comparatively compact modern large-flowered climber, producing a permanent woody framework and flowering laterals. Its uniqueness lies in the combination of dense white flowers and relatively restrained structure. Thus “vigorous” should be understood in relation to the plant’s ability to establish climbing shoots and renew its framework rather than as indicating the immense scale of an old Wichurana or Multiflora rambler. The flower is also unusually full for a common landscape climber, giving mature blooms a densely packed, nostalgic appearance.

The combination of near-white colour, large petal count, recurrent flowering, dense foliage and good disease resistance combined in rose that forms a leafy vertical mass capable of covering a narrow trellis, arch side, pillar or modest wall while retaining enough density at intermediate levels to avoid the bare-legged appearance that can affect some old climbers. The white flowers are particularly valuable against brick, dark timber, clipped evergreens or deep green foliage, where their intricacy remains visible from a distance. Because the colour is neutral and the plant is not excessively large, it also integrates readily into mixed perennial borders and formal white gardens.

FLOWERING

Rose 'Alaska' is a repeat flowering climber. The blooming habit is recurrent, in temperate climates it produces a strong first main flush followed by renewed flushes of blooms. The main flowering display normally develops in early summer once overwintered and newly produced laterals have matured, after which additional laterals and shortened shoots provide subsequent flowers through summer and, where autumn remains sufficiently mild, into early autumn.

The solitary flowers appear singly or in small clusters, usually containing two to five blooms together, with three to four flowering laterals below the terminal clusters and about seven to nine flowers can be found on a flowering shoot. Consequently, although an individual cluster is not enormous, a well-established plant can carry flowers at several levels simultaneously. The pale blooms stand lively against the plentiful green foliage, giving a luminous, snow shiny effect to the plant.

Deadheading after a flush can improve tidiness and may help direct resources into fresh lateral growth, although the senescent petals fall away cleanly. Where hips are not required, faded flower clusters can therefore be shortened to a strong outward-facing bud or leaflet. On mature climbers, flowering is improved by retaining several well-spaced principal canes and training some of them diagonally or more nearly horizontal where the support allows; this reduces excessive apical dominance and encourages numerous flowering laterals along the cane.

Flower bud:

The flower bud is long-ovoid and distinctly high-centred in shape. At the stage of opening it it typically reaches about 3 - 3.5 cm (1.2 - 1.4 in) from the base of the receptacle to the tip and 2 - 3 cm (0.8 - 1.2 in ) in diameter at its widest point. Its surface is leathery; as the sepals begin to separate, the visible petals are essentially white, corresponding to RHS White group 155B, while the basal region may retain a soft yellow-green tone. When approximately one-quarter open, both inner and outer petal surfaces of the petals remain white with a yellow-green basal zone.

There are five sepals, averaging about 2.5 cm (1 in) long by 7 mm (0.3 in) wide. Three of the five may carry weak foliaceous appendages, and the tips are apiculate. Their margins are entire but ciliate and bear abundant stipitate glands, especially near the edges. The outer sepal surface is leathery, while the inner surface is smooth to hoary; green is the dominant colour with occasional grey-red anthocyanic colouring. The combination gives the bud a conventionally pointed modern-rose outline before the many interior petals begin to expand.

The length of the peduncles varies broadly from about 1.5 to 7.5 cm (0.6 to 3 in), and are approximately 3 - 4 mm (0.12 - 0.16 in) in diameter, the colour is yellow-green with possibly some reddish pigmentation, and are moderately strong. Individual pedicels are longer, approximately 5 - 10 cm (2 - 4 in) long, relatively slender and somewhat weak, with numerous stipitate glands. This helps explain the slightly nodding or pendulous presentation of the open flowers that can occur once the very full bloom opens.

Bloom:

The fully open flowers of the rose variety 'Alaska' have a rounded, rosette shape. From the side, a newly opening flower is convex above and concave beneath; as it matures, the upper surface becomes flatter while the lower profile remains concave. Fully expanded flowers therefore develop the broad, shallow, many-petalled rosette appearance commonly described as nostalgic. The bloom may be held slightly downward, which can be especially attractive on arches and elevated trellises because the centre of the flower remains visible when viewed from below.

The flowers are medium to large sized, with a diameter of the open flower of about 7 - 8 cm (2.8 - 3.2 in) and a flower depth of about 4.5 сm (1.8 in), while under proper care and growing conditions the flowers tend to be larger, typically of about 8 - 10 cm (3.2 - 4 in) range in diameter. The flowers are full, there are approximately 80 petals normally present in the flowers. The arrangement is intentionally informal rather than rigidly symmetrical; outer petals open and reflex individually while the numerous smaller inner petals and petaloids produce a more intricate centre.

The predominant colour of the open flowers is white. Patent colour measurements place most petal surfaces around RHS White Group 155C, with the overall flower becoming very pale White Group 155D at anthesis and fading toward 155B after several days. A small amount of yellow-green can be visible at the very base while the flower is opening. Of particular ornamental interest is the occasional Red-Purple N66C tint sometimes observed on the outermost petals. In the garden this often appears simply as a delicate pink blush or pink-tipped outer petal, especially on young or weather-influenced flowers, while the centre remains white. Thus the plant should be regarded as a white, it is not absolutely pigment-free white under every growing conditions.

Individual flowers are capable of lasting approximately four days on the plant under the normal growing conditions with old petals falling cleanly. The ornamental display of an inflorescence or entire plant naturally persists much longer because buds open successively. In prolonged cool, wet weather the extreme petal count can slow opening, and good air circulation is therefore desirable, but under the prolonged rains the petals may show signs balling.

Petals:

The petals have obovate shape, with obtuse apices and cuneate bases, and they range considerably in size from approximately 2.2 - 4.0 cm (0.9 - 1.6 in) long by 1.7 - 4.0 cm (0.7 - 1.6 in) wide. Both surfaces of the petals are smooth, most of their margins are entire, but some of the innermost petals become ruffled, adding texture to the centre. Reflexing of the petals is pronounced and occurs petal by petal, including a double reflex, so that the outline of a mature flower becomes softer and more layered as it expands.

In addition to approximately 80 petals, typically there are about 15 petaloids present in the flowers of rose 'Alaska'. These smaller structures are approximately 1.2 - 2.2 mm (0.05 - 0.09 in) long, spatulate with obtuse tips, smooth in texture and often noticeably undulate at the margin. Their presence contributes significantly to the filled centre. The petals are not especially thick-looking despite the flower’s density, and the mature corolla retains a comparatively soft, romantic character.

Colour change with age is subtle. The main visual transition happens from a faint cream-green basal tone and occasional cool pink-purple outer tint toward a cleaner, paler white as the bloom expands and ages.

Fragrance:

Fragrance is present but should not be considered its main attraction. The scent of 'Alaska' is light and delicate, and varies according to temperature, humidity, flower age and the observer’s sensitivity. It is therefore better regarded as a pleasantly scented white climber than.

Reproductive parts:

Normally there are approximately 60 stamens present on the flowers of the rose variety 'Alaska', arranged regularly around the styles. The anthers are about 1.5 - 2 mm (0.06 - 0.08 in) long and wide, yellow-orange, and generally produce pollen in a moderate quantity. The filaments are approximately 5 - 7 mm (0.20 - 0.28 in) long and yellow.

There are also about 50 pistils present in the flowers of this rose. The stigmas are about 1 mm (0.04 in) in diameter, yellow, and positioned approximately level with or slightly above the anthers, while the styles measure about 5 - 9 mm (0.20 - 0.35 in) and are principally white with reddish pigmentation. The ovaries are small and pale, and the receptacle is funnel-shaped, approximately 7 mm (0.28 in) long by 11 mm (0.43 in) wide.

The hips (fruits) and seed formation and development are not specifically observed up to this date.

PLANT

Rose 'Alaska' is a woody, deciduous modern climber belonging botanically to Rosa and horticulturally to the complex modern Climbing roses class, although some sources call it a climbing Rosa hybrida, climbing Hybrid Tea or ClHT, while international trade records frequently use Large-Flowered Climber. These different labels are not contradictory so much as reflections of different classification systems: horticulturally, 'Alaska' behaves as a comparatively compact modern Large-Flowered climber, producing a permanent woody framework and flowering laterals, with an upright basal canes and comparatively dense branching and foliage.

The mature and well-established plants of rose 'Alaska' typically reach about 200 cm (6.6 ft) in height by 100 cm (3.3 ft) wide. The size of the plants may often approach about 250 cm (8.2 ft) under favourable conditions and vary in width from about 80 - 120 cm (2.6 - 3.9 ft) in spread, with climate, rootstock, pruning and training accounting for considerable variation. This scale makes 'Alaska' especially appropriate for medium arches, narrow wall panels, obelisks, entrance structures and fences where a larger 4 - 6 m (13.5 - 20 ft) rambler would be difficult to manage.

Like almost all garden climbing roses, it is not botanically self-clinging: canes must be tied to wires, trellis or other support. Newly planted specimens should be allowed to establish a framework for 2 - 3 years before severe pruning is attempted. Thereafter, the best policy is to preserve the healthy new main basal canes, remove dead, damaged and very old unproductive wood, and shorten flowered side shoots in late winter or early spring. Where possible, fanning of the main canes outward and training some diagonally encourages the growth of the flowering laterals over a larger surface.

THis rose would prefer a sunny, open and well ventilated place, in fertile humus-rich soil that retains adequate moisture while draining freely. Established plants benefit from an organic mulch and balanced rose fertilizer in spring, with a lighter second feeding after the first major flowering period where the growing season is long enough. Constantly waterlogged soil is unsuitable. In hot continental climates, reliable deep watering is preferable to frequent superficial irrigation, and a root-zone mulch helps moderate soil temperature.

Foliage:

The foliage is abundant on the plants of this rose, and the mature leaves are medium sized, measured at approximately 14 - 15.5 cm long (5.5 - 6.1 in) long and about 10 cm (4 in) wide. They are compound and imparipinnate, with dark green mature colouring, a semi-glossy upper surface and a matte lower surface. The texture is leathery, giving the foliage more visual substance than the thin, soft leaves of many old climbing roses.

The young leaves may carry medium grey-red anthocyanic pigmentation, creating a subtle contrast with the mature green canopy. The leaf mass is particularly valuable in a white-flowered rose because it provides a continuous dark background against which the blooms remain clearly defined. Dense foliage also helps the plant function effectively as a screen on fences or trellis panels even between flowering flushes.

Stipules are relatively well developed, approximately 2.5 - 3 cm (1 - 1.2 in) long and 5 - 6 mm (0.20 - 0.24 in) wide, winged at the base and apiculate at the tip. Their margins are ciliate and carry numerous stipitate glands.

Leaflets:

Mature leaves in the middle portion of the stem normally bear five leaflets, including the terminal leaflet. The terminal leaflet averages approximately 5.0 - 6.0 cm (2 - 2.4 in) long and 3.0 - 4.0 cm (1.2 - 1.6 in) wide and is elliptical in shape, with an acuminate tip, obtuse base and serrated margin; the type of serration is large and single. Slight undulation may occur, particularly on the terminal leaflet. Venation is reticulate and clearly integrated into the firm, leathery lamina.

The petiole is comparatively long, approximately 3.0 - 3.5 cm (1.2- 1.4 in), with a papillate surface, a limited number of marginal stipitate glands and usually two small prickles on the lower side. The rachis measures approximately 2.0 - 2.5 cm (0.8 - 1 in) and may likewise bear a few small prickles underneath. Individual petiolules are very short, approximately 2 - 3 mm (0.08 - 0.12 in), and typically are without prickles. The overall leaf structure is imparipinnate, serrate, leathery, with a semi-glossy adaxial surface - is entirely typical of a modern Large-Flowered climbing rose, although the predominance of five rather than seven mature leaflets proved sufficiently consistent for Kordes.

Wood:

The plant develops smooth, somewhat glaucous green to yellow-green canes, with reddish anthocyanic colouring possible on younger or exposed tissue. The main canes of this rose are typically about 8 - 10 mm (0.31 - 0.39 in) in diameter. Growth is upright and climbing, but the overall framework is bushier and more densely furnished with foliage than that of the unnamed pollen parent used in its breeding. Kordes commercial descriptions tend to present 'Alaska' as a moderate-growing climber. And practically it is so - shoots extend vigorously enough to form a climbing framework, yet the plant remains comparatively compact within the Large-Flowered Climber class. This makes annual training easier and allows renewal canes to be incorporated gradually.

Prickles:

There is a moderately to abundant quantity of the major prickles present on the main canes from the base and on the laterals from the main canes of the rose variety 'Alaska'. There are approximately seven prickles per 10 cm (4 in) of the stemlength, each about 7 mm (0.28 in) long. They are deeply concave in shape and smooth in surface texture. The young prickles are yellow-green; mature prickles remain greenish but may show grey-red anthocyanic coloration, eventually aging toward grey-brown. The armature is therefore significant enough to require gloves during tying and pruning, particularly on a rose grown around doorways or narrow passages. When used on an arch, pillar or frequently accessed trellis, shoots should be tied securely so that wind does not push prickly canes into the path.

Small prickles:

There can be few small prickles present on the canes of this rose: normally two small prickles occur beneath the petiole and a few beneath the rachis, while the short petiolules were observed without prickles. Thus 'Alaska' possesses both the large major stem prickles typical of a climbing rose and a much finer secondary prickles associated with the leaf axis.

Disease resistance and stress tolerance:

Rose variety 'Alaska' is regarded as having a very strong disease resistance, in particular to black spot (Diplocarpon rosae) and rust (Phragmidium spp.) under normal conditions, likewise has excellent leaf health. Kordes garden-rose breeding has placed unusually strong selection pressure on disease resistance and reliable performance without intensive fungicide regimes.

Powdery mildew requires slightly more attention. 'Alaska' is only lightly susceptible to mildew and able to regenerate well after infection, and is not completely immune. Resistance in roses is quantitative, and a plant that remains clean in one climate may develop limited disease under prolonged humidity, drought stress, excessive nitrogen, poor air circulation or heavy local inoculum pressure.

Winter performance is also good. This rose is recommended for growing successfully in climates similar to USDA zones 6 through 9. This suggests reasonable reliability to approximately the colder end of zone 6 when properly established, but survival of the root crown and survival of long climbing canes are not identical matters. In climates near the cold limit, a sheltered position, deep autumn watering before freeze-up, mulching or mounding around the crown, and protection from desiccating winter wind will help preserve more cane length and therefore improve the following year’s early flowering.

The principal commercial name 'Alaska' is evocative rather than botanical, associating the name with cold, snow and the cultivar’s reputed winter hardiness, but an original statement from Tim-Hermann Kordes explicitly documenting the naming decision was not disclosed.

'Future' is an established alternative commercial or exhibition name for this rose and appears alongside 'Alaska' in Kordes’ 2025 cultivar listing.

‘KO 05/2528-01’ is the earlier breeding or trial identifier associated with the selection and appears in international trial records alongside 'Future' and ‘KORjoslio’. Its “05” is consistent with the documented 2005 cross, although accessible breeder documentation does not provide a formal decoding of every component of the selection number, so the remainder should not be interpreted speculatively.

'Alaska' is an award-winning cultivar. It was honored with a 2014 gold medal at Den Haag/The Hague, and 2014 Gold Medal at Kortrijk/Courtrai.

For 2016, a World Federation of Rose Societies trial-winner report independently confirms 'Alaska'/'Future' (‘KORjoslio’, KO 05/2528-01) among the successful roses in the Lyon trials and gaining Lyon 1st Prize. This rose was also awarded with La Tacita - Gold (First Prize) Climber award La Tacita International Trials for New Roses in 2016.

A first prize at Baden bei Wien in 2017 was gained at Baden b. Wien Rose Trials.

And Best Climber award was received at Belfast Rose Trials in 2018.

ORIGIN OF THE VARIETY

Rose variety ‘KORjoslio’ / 'Alaska' was bred by Tim-Hermann Kordes at W. Kordes’ Söhne in Offenseth-Sparrieshoop, Germany, from a deliberate controlled cross carried out in the summer of 2005. The seed parent, or female parent, was the Kordes climbing rose ‘KORklemol’, commercially known as ‘Moonlight’. The pollen parent was an unnamed proprietary breeding line developed and owned by the same breeder.

Seeds from the 2005 cross were germinated during the following winter. Tim-Hermann Kordes evaluated the resulting seedlings at Offenseth-Sparrieshoop and selected the future ‘KORjoslio’ as a single superior plant in May 2006. The first asexual propagation took place in July 2006. Subsequent propagation by stem cuttings and grafting demonstrated that the distinctive characters remained stable and true to type.

Commercial introduction followed substantially later, in 2014, under the name 'Alaska' and in some markets 'Future'. The cultivar belongs to the Kordes Klettermaxe climbing-rose collection. European plant-variety-protection records list ‘Korjoslio’ under application number 2014/1620 and EU protection number 45781; a United States plant patent application was filed on 1 September 2015 and granted as PP27,925 on 25 April 2017.

BACKGROUND OF THE VARIETY

‘KORjoslio’ / 'Alaska' represents the modern disease-conscious development of the Large-Flowered climbers class. Its flower has an old-fashioned density and a rosette-like outline, but the plant was deliberately selected for recurrent flowering, abundant foliage and resistance to common rose diseases, reflecting the increasingly important expectation that ornamental quality should be achieved without constant fungicide intervention.

SUMMARY OF THE VARIETY

‘KORjoslio’ / 'Alaska' is a compact modern Climbing rose combining near-white, densely filled nostalgic flowers with a well-furnished upright framework and reliable repeat flowering, while the darkish semi-glossy, leathery foliage gives the pale flowers a strong visual background. This rose variety incorporated the following unique combination of characteristics:

  large, very double white flowers, sometimes delicately tinted pink or red-purple on the outermost petals;

  recurrent flowering on an upright, comparatively compact climbing plant, with excellent suitability for arches, trellises, pillars and small walls;

  very abundant, leathery, semi-glossy foliage combined with very good resistance to black spot and rust and generally strong garden health;

  useful cold-climate performance, with successful cultivation documented in USDA zones 6 - 9.

The propagation methods suitable for the rose cultivar 'Alaska' include stem cuttings and grafting; both methods are specifically documented in its patent. Because this remains subject to plant-variety rights or patent protection in some jurisdictions, propagation for commercial sale should be undertaken only where legally permitted or licensed.

COMPARISON WITH PARENTS

The seed parent of ‘KORjoslio’ / 'Alaska' is the rose variety ‘KORklemol’ / ‘Moonlight’, another climbing rose bred by Tim-Hermann Kordes. ‘Moonlight’ produces yellow flowers with pinkish edging, whereas 'Alaska' produces essentially white flowers. More strikingly, ‘Moonlight’ has only about 20 - 25 petals, while 'Alaska' develops approximately 80 petals, transforming the visual character from a relatively open double climber to a densely rosetted, full rose. 'Alaska' was also considered moderately vigorous relative to the high vigour of ‘Moonlight’. Also ‘Moonlight’ generally carries seven leaflets on mature mid-stem leaves, while 'Alaska' normally has five. ‘Moonlight’ is also the more fragrant, with a strong fruity-spicy fragrance while 'Alaska' is light to moderately scented.

The pollen parent - unnamed and unpatented cultivar has a cream rather than white flowers, the blooms of only medium size for a climbing rose, and has an arching growth habit with relatively sparse foliage. 'Alaska' was selected for larger white flowers and, importantly, a denser, bushier climbing plant.

COMPARISON WITH THE CLOSEST COMMERCIALLY AVAILABLE CULTIVAR

The most defensible comparison is with ‘Honeymoon’ (‘KORhemtra’), another commercially available Kordes climber. Both are compact modern climbers with pale, full flowers, repeat bloom and dark green foliage, and both suit relatively modest walls, fences and arches. ‘Honeymoon’ remains in commerce internationally and is generally reaching about 210 - 240 cm (7 - 8 ft) high, with clustered, full, cupped cream-white flowers carrying a distinct blush-pink centre.

The flowers of 'Alaska' are substantially more densely petalled with approximately 80 petals for 'Alaska' against approximately 50 for ‘Honeymoon’. Also 'Alaska' consequently produces a more packed, intricate rosette, while ‘Honeymoon’ is generally more openly cupped. Colour is also differs: 'Alaska' is white, with only occasional pale pink or red-purple colouring on outer petals, whereas ‘Honeymoon’ develops a cream to white bloom with a visibly blush-pink centre.

Foliage also differentiates them botanically. Mature leaves of 'Alaska' normally carry five leaflets and measure approximately 14 - 15.5 cm in length, while ‘Honeymoon’ has seven leaflets and longer leaves, approximately 17.5 - 18.5 cm. In the garden this contributes to the somewhat dense, leafy impression of 'Alaska', while ‘Honeymoon’ offers a softer cream-and-blush floral effect and a more pronounced sweet or old-rose fragrance in commercial descriptions. Gardeners prioritizing an essentially white, exceptionally full flower may prefer 'Alaska'; those wanting a warmer cream-white climber with prominent blush centres and fragrance may find ‘Honeymoon’ more suitable.

USDA 6

USDA Zone 6 - hardiness guide