PROPAGATION AND CULTIVATION Of Roses
Several important aspects of rose growing will be discussed in this chapter. To begin with, it will discuss the way new rose plants are propagated. Other aspects will include preparation of land for rose growing and method of planting. The other important topics of deliberations will be the cultural care the rose plants require throughout its useful existence. Proper feeding is another area in rose growing, • which demands special attention on the part of a rose grower. The water requirement of roses must also be studied so as to grow this flower successfully.
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Propagation
Roses can be propagated by various methods, both sexual as well as asexual or vegetative methods. The methods used for pro- pagation are from seeds, cuttings, layers, budding, grafting and tissue culture.
A. Seeds
Rose plants can also be raised from seeds. However, this method is followed normally for propagation of some rootstocks _ (in temperate regions) and species, or for raising new hybrid plants. Some wild species of roses (e.g., dog rose) used as rootstock in temperate countries produce numerous fruits (called hips) which contain enough seeds for raising new seedlings. Since there is hardly any crossing in nature, these species of roses produce more or less true- to-type seedlings (i.e. seedlings which do not show much difference from the mother). However, seedlings thus raised do not get ready for budding in the same season.
Rose seeds go through a period of 'after ripening' following harvest, during which phase these will not geminate. This is partly because the seeds are covered with a hard and imper- vious seed coat. A short description of how to get the seeds ger- minated may be given. The fruits or 'hips' are harvested when they ripe, i.e., when the colour changes from green to orange, red or yellow as the case may be. The seeds are extracted by cutting open. the hips. The hard seed coats have to be softened by scarification before .sowing. The procedure followed is to immerse the seeds in concentrated sulphuric acid for 30 minutes, following which these • are washed in water (preferably running water) for 2-3 hours. After scarification the seeds are put for stratification. For stratification, the seeds are sown in flats containing shredded and wet sphagnum moss, or wet vermiculite or moist sand. These can also be sown in plastic bags. These flats or bags are stored (before storing these are to be labelled indicating the parents used in the cross, in case of hybrid seeds) at 3 to 4°C for at least 4 weeks or until about 5 %, of the seeds start germinating. After this, the flats containing the seeds are transferred to a temperature of 18 to 21°C, where•the seeds finally germinate in about another 3 weeks. The seedlings, when these are large enough to handle, are transferred to a fertile growing medium for development till the first bloom appears.
Hips can also be harvested in the green stage for embryo culture. The embryos are extracted from the seed coat with the help of a sharp instrument and these are cultured in a nutrientagar media (similar to ones used for germinating orchid seeds), to obtain the rose seedlings. The whole operation is undertaken in a completely aseptic (i.e., sterile) condition to avoid fungal con- tamination.
In India, except few professional and amateur breeders, no other rose grower may need to propagate roses from seeds.
B. Cuttings
Roses are propagated from recently matured stem cuttings. This method of propagation is most useful, especially in India, to raise the rootstocks or understocks as this is called sometimes. Not many modern cultivars of roses can be propagated by cuttings, while some others which could be raised by this method, do not grow as, vigorously or produce as many flowers as a budded plant will dO. flower delivery in Delhi
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