Species or Wild roses.
Family Rosaceae > Subfamily Rosoideae > Genus Rosa.
Estimates of the number of species range from 33 to 300 with most people accepting around 140 although it may be lower.
From the temperate areas of the northern hemisphere, half come from Asia and China.
Fossil records go back to around 50 million years ago.
Roses hybridise easily and most now given species status are actually ancient hybrids of uncertain parentage.
Difficulties with the number of species is due to so many being very similar with some people giving them all a species name and others regarding them as variants.
They are shrubs, trailers or climbers up to 8 m high or ramblers nearly twice as high.
Branching stems can be erect, arching or lie on the ground.
Most have prickles, usually sharp, on the stems.
(Prickles grow from the surface layers of the stem while thorns are modified stems.)
The mostly deciduous leaves, on a petiole are alternately arranged in a spiral.
There are often tiny prickles (pricklets) on the petiole.
Paired leafy stipules, partly fused to the sides of the petiole base may have a few lobes.
The pinnate leaves, up to 15 cm long have 3 to 9 (13 or 15) leaflets.
Leaflets can be round, ovate, obovate, elliptic or heart or lance-shaped.
The lateral leaflets are on almost no petiolule and the terminal leaflet is on a longer one.
The edges typically have sharp teeth (serrated) and the lower surface of young leaves may have simple and glandular hairs.
New growth can be red or bronze and suckers may grow from the base.
Terminal inflorescences are a single flower or a cluster.
There may be few or no bracts on the peduncle but pedicels have no bracteoles.
There may be a few small prickles on the peduncle and receptacle.
The bases of the sepals, petals and stamens are fused to form a short hypanthium.
The tubular, round, bell or urn-shaped receptacle is up to 5 (10) mm long.
It may be smooth or have hairs, bristles or glands.
The 5 pointed sepals have hairs and/or glands on the edges and often the inner surface.
The 5 petals are mostly white or pink with a few red or yellow.
(Gardening Australia’s 2000 edition of Flora has 65 Species of Wild roses and of these 56% are pink or pink and white, 28% were white with or without some yellow, pure yellow were 11% and reds only 6%.)
Wild roses only flower once a year.
The numerous stamens, of different lengths have dorsifixed anthers opening through longitudinal slits.
The annular nectary disk is inside the stamens.
The inferior ovary has numerous separate carpels attached to the walls and base of the receptacle.
Each carpel has 1 pendulous ovule attached at the top of the ovary.
The style may have some hairs and the stigma is capitate (head-like).
The fruit is a variously shaped red, orange or black rose hip.
Inside it, and surrounded by long bristles, each carpel develops into a single-seeded achene.
The group also includes hybrids that closely resemble the species and some of these may be doubles and flower more than once in a season.
J.F.
