Seed Stratification At Home. Ways, Temperature, Timing

After harvesting, if it is necessary to multiply the crop, gardeners leave part of the seeds for sowing. No matter how good the weather was, immediately sowing the seeds would not form the seedlings. This happens because the embryo of the seed must necessarily go through a dormant period. The length of the dormant period is determined by the physiology of the seed, the growing season of plants (begins in spring, ends in autumn). If the seeds of all types of crops germinated immediately in the fall, the plants would die from meteorological conditions incompatible with the life of a young seedling.

There are special chemicals in the seed that block the development mechanism. These substances are called growth blockers or inhibitors. Gradually, their amount in the seed decreases and, instead of inhibitors, other chemicals called growth stimulants begin to affect the physiological processes in the seed. They awaken the embryo from dormancy (hibernation) and, including the development mechanism, ensure the germination, growth and development of the plant.

Content:

• What is seed stratification for?
• Types of stratification
• List of some plants whose seeds require stratification
• Stratification methods at home

What is seed stratification for?

The process of transition of seeds from dormancy to active life under the influence of external influences on the seed is called stratification. In fact, stratification is the preparation of the embryo for development. Certain conditions are necessary for the passage of seed stratification: favorable temperature and humidity of the environment. They cause softening of hard shells, their cracking, mucousness. Under the influence of moisture, the seeds swell, the physiological process of transferring complex high-molecular organic substances into simpler ones available to the embryo for nutrition begins.

Seeds will not sprout without passing through stratification, especially with a sharp change in temperature and humidity conditions in the middle and northern regions. In areas where climatic conditions practically do not change, seeds do not need a dormant period and can multiply year-round.

The duration of stratification of most plants varies within 1-6 months, but there are perennial crops, for which this period increases to 2 years (Table 1). Most flower crops, especially for spring sowing, also need stratification, a list of some of them is given in Table. 2.

The main goal of stratification is to reduce the dormancy period in artificially created conditions and to awaken the embryo to growth and development, that is, to get friendly shoots by a given time.

Table 1. Terms of cold stratification of perennial crops

Culture	Duration of stratification, days
Apricot	80-100, 120-150
Quince	70-90
Cherry plum	120-180, 130-150
Barberry, honeysuckle,	75-90
Hawthorn, viburnum	210-240
Common cherry, chokeberry	150-180
Felt Cherry	100-120
Walnut	50-80
Pear	75-100
Strawberry	20-30
Cotoneaster, rosehip	75-90
Schisandra chinensis	90-120
Magonia, grapes, prince	120-140
Almond	50-70, 120-140
Peach	100-120
Plum, blackthorn, rowan	120-180, 150-180
Bird cherry, lilac, aconite, catchment, hosta, anemone	30-50

Types of stratification

In practice, several types of stratification are used:

• cold;
• warm;
• combined;
• stepped.

The need, duration and type of stratification, as a rule, are indicated on the seed bag or in reference books. Dry seeds, cleaned of organic residues, are placed on stratification. Otherwise, in a humid environment, they can rot (apple trees, pears).

Cold stratification

For perennial seed crops, in conditions of a clear division into a cold and warm period, ending the growing season in autumn, cold stratification is usually used. This type of stratification is needed by the cultures of temperate regions. The seeds are placed in conditions with an air temperature from 0 to +4 ºС and a humidity of 65-75%.

The duration of stratification under these conditions can be 1-6 months. It is used for pome fruits, stone fruits, some vegetables, flowers and other crops. If the plants do not pass the cooling stage, they may not germinate in the spring. That is, stratification imitates subwinter sowing for some crops, when the embryo is provided with conditions for rest and subsequent awakening to growth and development.

Some seeds that require temporary exposure to low temperatures can sprout without stratification. But in this case, the seedlings will be sparse and not friendly (sea buckthorn, honeysuckle, strawberry).

Thermal stratification

Thermal stratification differs from cold short duration of passage. Usually vegetable crops undergo thermal stratification. Dry seeds can be in suspended animation for a long time. But an increase in temperature up to +18.. + 22 ºС and humidity not lower than 70% awaken life processes. For example: tomatoes, peppers, cucumbers, eggplants are enough to soak in warm water, leave in a warm place and in a day or two the seeds are squeezed, that is, germ sprouts appear.

Combined stratification

Combined stratification is applied to tightly similar seeds and seeds of some crops in areas where imitation of the changing seasons is needed to increase germination. Usually these are seeds of perennials with a thick, dense peel (hawthorn, viburnum, snowberry, yew, apricot, plum).

Hawthorn and viburnum seeds require long-term (7-8 months) stratification. To soften the dense shell and awaken the embryo, the seeds are first kept for 4 months at a temperature of +20.. + 25 ºС in a container with high humidity, and then for 5-6 months in a cellar or in a cool place at a temperature of 0.. + 5 ºС. For yew, some types of maple, a thermal stratification period of 1.0-1.5 months is sufficient, and then the seeds are placed on cold stratification.

Step stratification

This is the most complex type of multistage seed stratification. It consists of several low and high temperature cycles. So, the seeds of some types of peonies, actinidia are kept several times alternately at high and low temperatures.

Primrose, aquilegia, aconite are repeatedly frozen. Before sowing, for 5-7 days, their seeds are kept in water during the day at room temperature +18 ºС, and overnight they are placed in the freezer of the refrigerator. In this case, seed germination is high and friendly.

List of some plants whose seeds require stratification

Wrestler, or Aconite (Aconite). Some types: Altai wrestler; The wrestler is tall; Bearded wrestler; Antidote fighter; The nape wrestler. A two-step stratification is required:

1. +20.. + 25 ° С from 2 weeks to 3 months
2. 0.. + 5 ° С - 1-6 months

Anemone, or Anemone (Anemone). Some species: Blue anemone; Anemone is oak, or; White anemone; Altai anemone. A two-step stratification is required:

1. +18.. + 20 ° С - 2-3 months
2. +2.. + 5 ° С - 3-4 months

Cornflower (Centaurea). Some species: Blue cornflower, or Field cornflower; Fischer's cornflower. Stratification is required at a temperature of +1.. + 5 ° C - 1-2 months. Sowing can be done outdoors (April-May).

Carnation (Dianthus). Some types: Sand carnation; Clove herb; Lush carnation. Stratification is required at a temperature of +1.. + 5 ° C - 1-2 months. Sowing can be done outdoors (April-May).

Jeffersonia. Some types: Jeffersonia doubtful, Jeffersonia double. A two-step stratification is required:

1. +8.. + 10 ° С - 6 months
2. 10/30 ° С * - 1 month

Seeds quickly lose their germination. Sowing is carried out after harvest in the middle of summer.

Delphinium, or Larkspur, or Shpornik (Delphinium). Stratification in sand at a temperature of +5.. + 6 ° C is required from 2 weeks to 1 month. The optimum temperature for seed germination is +10.. + 15 ° С

Bell (Campanula). Stratification in sand at a temperature of +1.. + 5 ° C is required. Sowing in spring, shoots at +10.. + 15 ° С

Clematis, or Clematis. Some species: Clematis Drummond, Clematis pungent, Clematis whorls, Clematis ligous-leaved. A two-step stratification is required:

1. Stratification in sand or peat at 0.. + 5 ° С - 2-3 months
2. Germination 20/30 ° С * - 1-2 months

Seed germination is uneven.

Smelly Black cohosh, black cohosh or ordinary (Actaea cimicifuga). A two-step stratification is required:

1. 20 ° C - 2-3 months
2. 4 ° C - 2-3 months

Germinate at 12 ° C.

Peonies (Paeonia). A two-stage stratification is required.

Peony evading, or Peony extraordinary, or Peony Maryin-root (Paeonia anomala).

1. 18/30 ° С * - 1 month
2. +5.. + 7 ° С - 3.5 months

Milk-flowered peony (Paeonia lactiflora).

1. 18/30 ° С * - 1.5 months
2. +5.. + 7 ° С - 2-3 months.

Thin-leaved peony (Paeonia tenuifolia).

1. 12/30 ° С * - 4 months
2. 5 ° C - 1.5 months

Phlox (Phlox). Some species: Phlox adorable, Phlox Douglas, Phlox subulate. Requires sand stratification at +1.. + 5 ° С - 2-4 months. The optimum temperature for seed germination is +5.. + 12 ° С.

Liver, or coppice (Hepatica). A two-stage stratification is required.

1. +18.. + 20 ° С - 1 month
2. 12 ° C - 3.5 months

Seeds with a developed embryo germinate only at 12 ° C.

Stratification methods at home

Dry stratification

• Seeds laid for stratification are preliminarily disinfected. You can soak for 0.5 hours in a 0.5% solution of potassium permanganate. Then rinse in several waters at room temperature. Dry, put in plastic bags, provide with a detailed label indicating the type, grade and date of laying for stratification. Place the bags on the upper shelf of the refrigerator or in a room with a temperature of 0 - +3.. + 4 ºС before sowing in the ground.
• Disinfected, dried seeds in linen or polyethylene bags are placed in a plastic container, the lid is tightly closed and secured with tape. The prepared package is buried in the snow until it melts. With the onset of heat, they are moved to the basement or to the lower shelf of the refrigerator before sowing.

Stratification in cabbage stumps

Ideal for cold stratification at home.

Separate the cabbage stubs from the heads. We chop off the roots. In the resulting stump, remove the core. Fill the resulting container with seed. Close the cover tightly and fix it with tape from the remains of the stump. We bury the "capsule" with seeds (like our grandfathers with gold coins) in the ground vertically into a hole deep into the bayonet of a shovel.

We cover it with earth on top. We set a number marker, and in the diary under its number we write down information about the seeds, indicating the type and variety of the crop, the time of setting and the end of stratification. In the spring, when the top layer of the soil is heated to the temperature required for the culture, we dig out a stump with seeds and sow in a prepared bed.

Wet stratification

• Sanding … We prepare containers with a substrate, which can be large river washed sand, rotted sawdust, peat, moss. It is very important that the seeds are thoroughly washed from organic debris, disinfected and dried. Fill the containers 2/3 with a moist substrate. We lay out the prepared seeds and cover them with the substrate on top. Simultaneously with moistening, the substrate must be treated against fungal infection with one of the biofungicides: trichodermin, phytosporin, alirin-B and others. Processing methods are usually indicated on the packaging. We close the containers with a lid and place them in a plastic bag to preserve moisture. Packaged containers are placed on the lower shelf of the refrigerator. The temperature should be within the range of +3.. + 4 ºС. With this storage method, at the end of the stratification period, the bags are transferred to conditions with reduced temperatures down to +1 ºС. Besides,the containers are periodically examined, monitoring the condition of the seeds and, if necessary, moisten the substrate.
• Stratification in cloth rolls. On strips of natural fabric 10-12 cm wide and 30-35 cm long, lay out a thin layer of moss or cotton wool. Place the seeds carefully. We bend the long sides of the fabric strip, which will cover the seeds on top, and roll up the roll. We tie it up, put it in water to saturate it with moisture. Gently squeeze out excess water. We wrap the roll in a plastic bag and place it on the bottom shelf of the refrigerator. We supply each roll with a label or number, and in the garden diary with a detailed description (see above). During stratification, the rolls are systematically checked for moisture. We control the condition of the seeds. When a fungal infection is detected, we wash the seeds, disinfect, dry them and repeat the whole process of laying for stratification on new sections of material.

Winter sowing

Some crops are sown and planted in the fall (podzimny sowing) in the soil, where they are stratified in natural conditions (winter garlic, green, certain varieties of salads).

In addition to those described, there are other ways to carry out seed stratification. Remember! Stratification will save you from the spring suffering associated with low sprouting or none at all.