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Stratification   Agronomy - Horticulture ]

Dictionary of botanic terminology
index of names

A pre-germinative treatment to break dormancy in seeds and to promote rapid uniform germination based on the simulation of the natural conditions that a seed must endure before germination.
The seeds of many of native species of plants, deciduous and evergreen trees and shrubs along with some perennials and herbs are incapable of germinating immediately after they are harvested and will not germinate without a pre-treatment known as stratification.
Stratification simulate the natural conditions that a seed must endure before germination. Some seeds are incomplete and require a further period to complete the development of immature parts; some other have built-in dormancy mechanisms (like mechanical barrier to water or physiological "block") that prevent them from germinating (sprouting) until growing conditions are favourable. Depending on the species, seeds will not break dormancy under too wet or too dry growing conditions, imminent winter conditions, or high temperatures. For seeds that require a development period, dry storage will usually suffice. Among other methods of treatment of seeds, stratification (warm, cold, or variable stratification) is used to remove mechanical moisture barriers and physiological blocks.

(Seed bagged)

The stratification, is an old and simple practice of stimulating seed to germinate by placing alternate layers of a moist media and seed.
The modern method is to thoroughly mix seeds in moist media like peat moss, vermiculite, perlite, composted bark, sawdust, or potting media to simulate the natural conditions it would normally receive from its native environment. The mixture is stored in sealed containers such as polyethylene bags. The bags are simply stored at room temperature to provide the moist warm treatment. They can be placed in the household refrigerator if a moist cold treatment is required.
There are several types of stratification depend on what that seeds would normally experience in nature.
  Warm-wet. Seeds that require a warm moist treatment to induce germination can be stored at a room temperature, Keep out of the sun!
Cool-wet. Seeds that require a cold moist treatment. Can be stored in the vegetable compartment of the refrigerator for four to twelve weeks.
Warm-cool-warm-wet. Depending on the species, some need a combination of warm and cool treatments followed by a warm to germinate.
Warm-cool-warm, wet and dry Some other specie need a combination of warm- cool in moist medium followed by a period in which the medium and seed are allowed to dry for one to a few month repeating this cycle for the necessary number of treatments followed by a warm to germinate.
Stratification Instructions:
A) Necessary items before beginning:
Sterile medium (peat moss, vermiculite, perlite, or potting media)
Plastic labels and waterproof pen
Sterile Plastic Zip Lock freezer bags or plastic containers with tight fitting lids.
B) Label
  Label both the containers and plastic stakes with a waterproof pen. Include the stratification date started and when they are due to be removed from stratification.
C) Scarification.
  Some seeds have a mechanical barrier to water, which is required for germination. These may require scarification.
D) Soaking
  Further, some seeds have a hormonal or chemical  inibition to germination. These may require soaking.
E) Mixing the stratification medium.
  Use 10-20 times the volume of medium vs. seed volume. Your stratification medium should be moist to the touch, but not soaking wet. Moisture is obviously a key factor in the stratification process.  High moisture levels in the sealed containers, however, causes fungus growth that can harm the seed, mixing a fungicide in the medium is a good prevention
F) Stratify
  Make note on your calendar when you place your seeds into stratification and when to remove them.  Place the sealed containers into the proper cold or warm stratification environment. Seed should not stay in stratification many months past its recommended stratification time as it will use up its energy reserves and die. Even at low moisture levels some of the seeds might  germinate in the sealed containers; these seeds will grow normally, if they are planted carefully
f) Remove and Sow
  After the required time period (or after germination is noticed), remove the seed and sow

If you don't want to stratify in the 'fridge, then you can always use the nature's way and sow in the Autumn planting the seeds directly into a nursery bed or pot for germination the following Spring usually satisfies a seed's requirement for cold stratification. This means you can skip all the above outlined pre-treatment in your refrigerator as the over-wintering of the seeds in the earth accomplishes the same thing.







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