Commercial Floriculture

Growth and Flowering of Roses

There are many factors which affects the growth and flowering of roses, viz.,
Genetic or inherent factors
Environmental factors (light, temp., RH, Aeration, and CO2.)
Managerial factors (nutrition and soil factors, pruning, pinching, defoliation,plant growth regulators).

1. Genetic or inherent factors:
• Like other plants, growth and flowering behavior of roses is governed by genetic factors.
• Significant difference in growth & flowering of different rose species and cultivars have been observed which are due to genetic variation existing among them.
• There are tall cultivars growing several meters high and are suitable for planting in back drop as hedge, on the other hand, Miniature roses with dwarf habit and producing small flowers.
• Several cultivars are bushy in nature while many are climbers and ramblers, similarly there is wide, variation with respect to days to flowering, flowering duration, size, quality and flowers etc.

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2. Environmental factors:
• Moderately cool climate with bright sunshine and free aeration/ventilation is very good for rose growing.

  I. Light: Light is one of the most important factors influencing the flowering, light intensity, duration and quality of light plays an important role.

  1. Light intensity:
• 6000-8000 ft candles or 6-8 K is good for roses and it was observed that, during winter season flower colour is better than any other season.
• During summer flower colour fades.
• In general rose requires bright sunshine for the whole day. It should be free from shades of trees and protected from the strong winds.
2. Temperature:
• It is another imported factor regulating growth and flowering of roses.
• It affects both quality and quantity of flowers.
• Mild temperature is very important about 15.5oC is ideal for its cultivation because of this reason in winter we get good crop.
• On sunny days 25-30oC. Whereas on cloudy day it must be 18-20oC.
• However a maximum of 28oC in day and 15-18oC in the night will be ideal for rose production.
3. Humidity:
• RH is very important with respect to pests and disease incidence especially mildews and black spot as they are closely associated with high RH in greenhouses as the high humidity results in condensation of water on flowers and leaves.
• About 60% RH is the most ideal for rose production.
4. Aeration/Ventilation:
• An exchange of air in greenhouse is desirable for normal growth and development of roses.
• Air circulation ensures an adequate supply of CO2 and O2 for physiological process occurring in the plants and also reduces the RH.
5. Carbon dioxide:
• In western countries an additional 1000-3000 ppm of CO2 are ejected into the greenhouse to increase the growth of the plant as well as quality flower production.
• It also helps in increasing the stem length and reduces the incidence of flower abortion.
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