1. Seed Dormancies
Plant Propagation

2. Types of Seed Dormancies
Physical
Mechanical
Chemical
Morphological
Physiological
Photodormancy
Double Dormancy

3. Physical Dormancy Cause Treatments Seed coat is impermeable to water.
*Scarification
A – Acid
B – Mechanical
C – Hot Water
Examples: Honeylocust, Black Locust, and Hawthorne

4. Mechanical Dormancy Cause Treatments
Seed coverings (seed coat and/or pericarp) are so rigid that the embryo can’t expand and germinate. Embryo cannot physically penetrate the seed coverings.
*Remove seed coverings (such as walnut shells and the pits of stone fruits).
*Warm stratification (warm temps and moist conditions) in an non-sterile medium will enhance microbial softening of the seed coverings.
Examples: Black Walnut, Peach, and Pepper

5. Chemical Dormancy Cause Treatments
Chemicals in the seed coverings and/or fruits inhibit the germination of the embryo.
*Remove the seeds from the fruit or seed coverings.
*For seeds with the germination inhibitor present in the seed coat, leach the seeds in water (many desert plants have this type of dormancy).
Examples: Fruits or juices strongly inhibit the germination of Citrus, Apple, Pear, Grapes, Cucumber, and Tomato.

6. Morphological Dormancy
Cause
Treatments
Embryo is underdeveloped and undersized at the time of seed dissemination. This type of embryo is referred to as being rudimentary.
*Warm stratification
Examples: Poppy, Buttercup, Ginseng, and Rhododendron.

7. Physiological Dormancy
Cause
Treatments
Embryo is “normal size” but factors within the embryo itself inhibit germination (dormant embryo).
*Cold stratification
A – moist
B – aerated
C – proper temperature
D – proper time
Examples: Peaches, Lilac, Redbud, some Oaks, and many other woody ornamental species.

8. Photodormancy Cause Treatments
Seeds will not germinate until they are exposed to a certain amount of red light. Rototilling an area will bring will bring buried weed seeds to the surface where they will be exposed to sunlight (which is composed of red light along with the other wavelengths of light).
*Expose seeds to red light. Seeds must first be in an imbibed state.
Examples: many weed seeds.

9. Double Dormancy Cause Treatments
Combination of several different kinds of dormancies present in a seed at the same time.
*Sequential treatments to handle each type of dormancy.
Examples: Redbud

10. The End