Rosa gigantea
Collett ex Cr,p.
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Joseph Dalton Hooker (1817-1911) und William Botting Helmsley (1843-1924), no known copyright restrictions (public domain)
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(c) Tiffany, some rights reserved (CC BY-NC)
Summary
Source: WikipediaRosa gigantea is a species of rose native to northeast India, northern Myanmar and southwest China (Yunnan) in the foothills of the Himalaya at 1000–1500 m altitude. It is sometimes considered to be a variety of Rosa odorata, as R. odorata var. gigantea. As its name suggests, it is the largest species of rose, climbing 20 m or more into the crowns of other trees by means of its stout, hooked thorns, and with a trunk up to 50 cm diameter. The leaves are semi-evergreen, 15–25 cm long, pinnate, with usually 7 leaflets, each leaflet 4–8 cm long. The flowers are white, creamy or yellow, the largest of any wild rose, 10–14 cm diameter. The hips are yellow or orange, 2.5–3.5 cm diameter, hard, and often lasting through the winter into the following spring, often still present at the same time as the next years' flowers. Another rose, described from Manipur in 1888 as R. macrocarpa and R. xanthocarpa by Sir George Watt, an authority on Indian roses, is now generally considered to be the same species as R. gigantea. The distinct characteristics claimed for R. macrocarpa (deeper yellow flowers, larger foliage with 4 to 7 leaflets and large yellow fruits) are not consistent. After gene sequencing was carried out in 2018, it was found that Rosa roxburghii is closely related to Rosa odorata var. gigantea.
Description
A large climbing plant. It can climb 20 m tall. It has stout hooked thorns. The stem can be 50 cm across. The leaves are 15-25 cm long. They have leaflets along them. There are usually 7 leaflets and each one is 4-8 cm long. The flowers are white or yellow. The rosehips are yellow or orange and 2.5-3.5 cm across.
Edible Uses
The fruit can be eaten raw or cooked and is notably large for a rose — up to the size of a small apple and up to 30mm in diameter — though only a thin layer of flesh surrounds the many seeds. Care should be taken when eating the fruit due to known hazards. The very fragrant petals are used as a flavouring in sorbets, confections, and similar preparations. The seeds are a good source of vitamin E and can be ground and mixed with flour or added to other foods as a supplement; seed hairs must be removed before use.
Medicinal Uses
The fruit is a very rich source of vitamins and minerals, particularly vitamins A, C and E, flavanoids, and other bio-active compounds. It is also a fairly good source of essential fatty acids, which is unusual for a fruit. It is being investigated for its potential to reduce the incidence of cancer and to halt or reverse cancer growth.
Known Hazards
There is a layer of hairs around the seeds just beneath the flesh of the fruit. These hairs can cause irritation to the mouth and digestive tract if ingested.
Distribution
It is a temperate plant.
Where It Grows
Asia, China, Himalayas, India, Myanmar, Northeastern India, SE Asia,
Cultivation
Succeeds in most soils, preferring a circumneutral soil and a sunny position. Grows well in heavy clay soils. Dislikes water-logged soils. This species is not very hardy in Britain, tolerating only light frosts. Another report says that some provenances might tolerate occasional lows to -10°c. It succeeds outdoors only in the milder areas of the country and is best grown against a south-facing wall. Grows well with alliums, parsley, mignonette and lupins. Garlic planted nearby can help protect the plant from disease and insect predation. Grows badly with boxwood. Closely related to Rosa odorata, and considered to be no more than a subspecies of that plant by some botanists. The edible fruit is sometimes sold in local markets in the Himalayas. There is at least one named form, 'Belle Portugaise' has flowers 10 - 12cm across, the petals are rated very highly for their culinary uses. Hybridizes freely with other members of this genus. Plants in this genus are notably susceptible to honey fungus.
Propagation
Rose seed often takes two years to germinate, as it may require a warm period following a cold spell to mature the embryo and break down the seedcoat. One way to shorten this time is to scarify the seed and place it for 2–3 weeks in damp peat at 27–32°c until it has imbibed, then keep it at 3°c for the following 4 months, by which time germination should begin. Seed harvested green — fully developed but before drying on the plant — and sown immediately may germinate in late winter, though this method had not been fully tested as of 1988. Seed sown fresh in a cold frame sometimes germinates in spring but may take 18 months. Stored seed should be sown as early in the year as possible and stratified for 6 weeks at 5°c; it may still take 2 years to germinate. Prick out seedlings into individual pots when large enough to handle. Plant out in summer if plants exceed 25cm, otherwise overwinter in a cold frame and plant out in late spring. Half-ripe cuttings with a heel taken in July in a shaded frame give a high success rate; overwinter in the frame and plant out in late spring. Mature cuttings of the current season's growth, selected as pencil-thick shoots around 20–25cm long in early autumn, can be planted in a sheltered spot outdoors or in a cold frame; they take up to 12 months to establish but succeed at a high rate. Suckers can be divided during dormancy and planted directly into permanent positions. Layering takes 12 months.
Other Uses
None known.
