This type of dormancy may be satisfied naturally if seeds are sown outdoors in the fall. Warm stratification is similar except temperatures are maintained at 68 to 86°F depending on the species. Force the bud to develop the following spring by cutting the stock off 3 to 4 inches above the bud.
To achieve germination with seeds having both external and internal dormancy, the seeds must first be scarified and then stratified for the appropriate length of time. If the treatments are administered in reverse order, the seeds will not germinate. After completing these treatments, plant the seeds under the proper environmental conditions for germination. Temperature affects the germination percentage and the rate of germination. Some seeds germinate over a wide range of temperatures; others have a narrow range. Many species have minimum, maximum, and optimum temperatures at which they germinate.
Biennials, such as carrots, complete their life cycle in two seasons. In a biennial’s first season, the plant has a vegetative phase, whereas in the next season, it completes its reproductive phase. Commercial growers harvest the carrot roots after the first year of growth and do not allow the plants to flower. Perennials, such as the magnolia, complete their life cycle in two years or more. Micropropagation is a method of propagating a large number of plants from a single plant in a short time under laboratory conditions.
The first step in the germination process is the imbibition or absorption of water. Even though seeds have great absorbing power due to the nature of the seed coat, the amount of available water in the substrate affects the uptake of water. An adequate, continuous supply of water is important to ensure germination.