Botanical description

What is a rose ?

The roses are shrubs or scandent shrubs, cultivated or wild. Theirs stems are often armed with prickles, their leaves are composed and theirs flowers are more or less fragrant and multicolor.

They belong to the genus Rosa, within the family Rosaceae. They are native to the temperate regions of the northern hemisphere.

 

The botanical classification of indigenous roses includes 150 species in the genus Rosa. Over the course of time, however, natural and spontaneous crosses have been produced and have created many hybrids. In addition, man has intervened since the 19th century : species and natural hybrids have been used to obtain yet more new varieties, called cultivars (from cultivated varieties).

 

Today, there are many species of rose... and several thousand varieties !

 

Illustration "Rosa canina"
from Flora von Deutschland, Österreich und der Schweiz
(Prof. Dr. Otto Wilhelm Thomé - 1885, Gera, Germany)

 

1 : Bouton  
2 : Pétale
3 : Fleur coupée en long avec vue des étamines, des sépales, du réceptacle, du pédoncule (ou pédicelle)
4 : Stigmates recouvrant l’orifice du réceptacle
5 : Carpelle avec au sommet, stigmate, puis le style puis l’ovaire recouvert de poils calicinaux
6 : Graine
7 : Ovaire coupé en long avec vue sur l’ovule
A : Tige pourvue d’aiguillons
B : Cynorrhodons

Constitution du rosier

  • General aspect

The rose can be miniature (less than 0.50m high), bush (from 0.40 m to 1.10m), shrub (from 1m to 2m), tree or climbing.

  • Stems

Their long, arching canes are of variable size and colour. They carry prickles which can differ greatly from one variety to another.

  • Leaves

The leaves are alternate and mostly deciduous. They are made up of leaflets, always an odd number (from three to seven) and have indented leaf-blades.

  • Flowers

The flowers can be white, pink, red, yellow and sometimes variegated or bicoloured. Usually scented, they are either single or in corymbs of several flowers. The flowers are composed of five sepals and at least one layer of 5 petals as well as numerous stamen and carpels.

  • Rose hips

The floral receptacle contains the carpels and supports, at its extremity, the other parts of the flower. At maturity it forms a fleshy, false fruit called a rose hip.

  • Roots

Roses develop highly filamentous root structures in soil in order to anchor the plant and absorb the nutrients necessary for growth.
The roots of modern roses often belong to a different variety (root-stock) to that of the aerial parts. Grafting is the technique which allows the largest number of commercially useful plants to be produced.