Rose Rosa rugosa ‘Alba’

Rosa rugosa ‘Alba’ is a white-flowered form of the Rosa rugosa species long prized for its dazzling single blooms, tomato-like hips, ironclad cold- and salt-tolerance, and almost bullet-proof disease resistance. Native to the windswept seashores of East Asia, it has travelled the world as a hedging, stabilising and breeding plant, yet remains easy enough for a first-time rose-grower.

FLOWERING

This rose has a once flowering habit, blooming early in the season in the late spring or early summer. After the flowering large and decorative hips are formed, which add seasonal diversity to the plant, especially look great against white snow in winter.

The flowers are medium sized to large, about 9 cm (3 inches) in diameter when fully open. The are single, typically having 5 petals per bloom, occasionally 6. The flowers are pure white, with silky-textured petals and flatten with age, revealing a bunch of yellow stamens; the number can exceed 250 stamens per flower.

Flowers appear singly or in small clusters of 2 - 4 blooms together. The fragrance is strong, with clove character.

After the flowering large and decorative rose hips (fruits) are formed of bright red colour. They are about 2.0 – 2.5 cm in diameter, spherical and shorter than wide and have smooth surfaces. The hips of this rose are rich in β-cryptoxanthin at 1.2 mg 100 g⁻¹ FW and the mature single plant can bear up to 2 – 3 kg of fruits per growing season. The hips are ready for harvest when fully coloured; after harvesting needs to dry at ≤45 °C to preserve vitamin C.

PLANT

Rosa rugosa ‘Alba’ is classified as Rugosa rose. It has a powerful, upright and broad growth character. It grows on its own roots and tends to send sucklers, therefore when needed to limit its spread it is recommended to use root barriers or grow in large bottomless containers. Usually it grows broader than taller, the mature and well-established plant has a height of about 100 - 120 cm and the width of about 120 - 150 cm if left unpruned.

Young canes of Rosa rugosa ‘Alba’ are green, maturing to reddish-brown; prickles are thin, straight and sharp, up to 1 cm in length. For this rose recommended late-winter rejuvenation: cut oldest canes to 20 cm; after flowering to control height perform pruning to form a shape and to enable air circulation.

For this rose it is best to choose a sunny, well-drained spot with at least 30 cm soil depth suffices - in such conditions you will maximize hips harvest and ensure maximal growth. But it also grows well in shade; seaside or road-salt exposure is acceptable as well. Field trials show optimal growth on sandy loam, pH 5.5–7.0, with organic matter ≥ 3 % but tolerates NaCl up to 150 mM without growth penalty. Mature and established shrubs endure drought very well. Note that over-fertilisation of this rose weakens its stress tolerance.

The foliage has its distinctive ‘rugosa’ appearance - with wrinkled surface of the leaves. The foliage is dense, medium sized, dark glossy-green above and grey-pubescent beneath; the number of leaflets is typically 7, including the terminal leaflets.

The disease resistance is excellent, it is very resistant to Black spot (Diplocarpon rosae), mildew, rust and botrytis. It also has good resistance to rose rosette virus as it prefers smooth-canned roses. As an early flowering and light coloured rose it attracts Japanese beetles and its silky petals can be spoiled by aphids.

Rosa rugosa ‘Alba’ has very good disease resistance, with colds down to −34 °C (USDA Zone 3) no cane dieback observed in Minnesota trials.

With its forgiving nature, snow-white blooms and rich vitamin-C fruits, Rosa rugosa ‘Alba’ offers an ideal shrub rose for gardeners who want beauty with almost no chemical inputs.

The Latin rugosa = “wrinkled,” while the cultivar epithet ‘Alba’ indicates white flowers, first noted in Japanese herbals c. 1790. Formal listing occurred in the Journal of the Royal Horticultural Society in 1899 (no DOI). Synonyms include: R. rugosa f. alba Ware, R. rugosa var. alba Regel, and trade name ‘White Ramanas’.

Victorian (ARS), Central Arkansas Rose Society Show, 1998;

Dowager Rose Queen (ARS), Corvallis Rose Society Show, 1999;

Dowager Rose Queen (ARS), Jersey Shore Rose Society Show, 1999;

Dowager Rose Queen (ARS), Portland Rose Society Spring Show, 1999;

Dowager Rose Queen (ARS), Clay County Rose Society Show, 2000;

Dowager Rose Queen (ARS),Fox River Valley Rose Society Show, 2000;

Dowager Rose Queen (ARS), Greater Cincinnati Rose Society Show, 2000;

Dowager Rose Queen (ARS), Portland Rose Society Show, 2000;

Dowager Rose Queen (ARS), Clay County Rose Society Show, 2001;

Victorian (ARS), Northeastern Ohio Rose Society Show, 2001;

ORIGIN OF THE VARIETY

Rosa rugosa ‘Alba’ is a naturally occurring white-flowered selection of the beach rose R. rugosa Thunb. Thanks to its extreme tolerance of maritime winds, saline soils and freezing winters, it has become both a horticultural mainstay and, in some regions, an invasive shrub.

USDA 3