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Roses can withstand a wide range of temperatures. In general, hot, dry conditions are preferable to humid conditions. Roses adopt winter dormancy when temperatures fall below zero at night and less than 10°C in the day. With minimum night temperatures of 10°C and correspondingly warmer temperatures of 18°C to 25°C during the day, roses will happily flower non-stop for 12 months of the year, providing they have been watered, fertilized and groomed as required.
Roses require considerable light to be able to flower. Their flowering ability is reduced in direct proportion to reduced light. Sufficient light can mean either intensive light on shorter days, or more diffuse light as found in Europe on long days under an overcast sky. To flower freely, roses require direct light for about five hours in the morning when planted east of a building, or in the afternoon when planted west of a building. In situations with less than four hours of direct light, fewer or no flowers will be produced and the foliage becomes soft and susceptible to diseases.
The condition of the soil can always be adjusted to suit roses. Sandy clay is ideal, as it offers good aeration as well as water retention. To improve plain clay, add sand, gravel or coarse organic material; and to upgrade sandy soil, add water-retaining materials such as peat moss, coir or other organic matter. Lime can be added to acidic soil and flower of sulphur to alkaline soil to achieve the desired, neutral pH. Read more about soil preparation in ‘Planting procedure’
Although roses are ‘water wise’ and able to adjust to the quantity of water available, they cannot generate new stems and flowers during the growing season without regular watering. The broad, basic requirement is 10 litres per plant per week. This varies according to the size of the plant and the condition of the soil. Take a more detailed look at watering in ‘Rose care’.
Roses grow and flower well in most types and sizes of pots or containers, particularly the free-flowering Colourscape varieties. For more details read ‘Growing roses in containers’.