Sometimes temperatures are used in connection with day length to manipulate the flowering of plants. Chrysanthemums will flower for a longer period of time if daylight temperatures are 50°F. The Christmas cactus forms flowers as a result of short days and low temperatures.
Temperatures alone also influence
flowering. Daffodils are forced to flower by putting bulbs in cold storage
in October at 35 to 40°F. The cold temperature allows the bulb to
mature. The bulbs are transferred to the greenhouse in midwinter where
growth begins. The flowers are then ready for cutting in 3 to 4 weeks.
Low temperatures can result in poor growth. Photosynthesis is slowed down at low temperatures. Since photosynthesis is slowed, growth is slowed, and this results in lower yields. Not all plants grow best in the same temperature range. For example, snapdragons grow best when night time temperatures are 55°F, while the poinsettia grows best at 62°F. Florist cyclamen does well under very cool conditions, while many bedding plants grow best at a higher temperature.
Buds of many plants require
exposure to a certain number of days below a critical temperature (chilling
hours) before they will resume growth in the spring. Peaches are a prime
example; most cultivars require 700 to 1,000 hours below 45°F and
above 32°F before they break their rest period and begin growth.
This time period varies for different plants. The flower buds of forsythia
require a relatively short rest period and will grow at the first sign
of warm weather. During dormancy, buds can withstand very low temperatures,
but after the rest period is satisfied, buds become more susceptible to
weather conditions, and can be damaged easily by cold temperatures or
Oregon State University,
News and Communication Services
Review of Temperature
Effects on Plant Growth: