Stratification of seeds at home
After harvesting, if necessary, propagation of the culture, gardeners leave part of the seeds for sowing. No matter how good the weather, immediate sowing of seeds would not form seedlings. This happens because the seed germ must pass through a period of rest. The length of the dormant period is determined by the physiology of the seed, the vegetation period of the plants (begins in spring, ends in autumn). If the seeds of all kinds of crops sprouted right there in the fall, the plants would die from weather conditions incompatible with the life of a young seedling.
The seed contains special chemicals that block the development mechanism. These substances are called blockers or growth inhibitors. Gradually, their amount in the seed decreases and other chemicals called growth stimulants begin to act on the physiological processes in the seed to replace inhibitors. They awaken the embryo from rest (hibernation) and, including the development mechanism, provide germination, growth and development of the plant.
Why is seed stratification necessary?
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. For the passage of stratification of seeds, certain conditions are necessary: favorable temperature and humidity of the environment. They cause softening of hard shells, their cracking, mucus. Under the influence of moisture, the seeds swell, the physiological process of converting complex high molecular weight organic substances into simpler ones that are accessible to the embryo for nutrition begins.
Without stratification, the seeds will not sprout, especially with a sharp change in the temperature and humidity conditions of the middle and northern regions. In areas where climatic conditions practically do not change, the seeds do not need a dormant period and can reproduce year-round.
The duration of the stratification of most plants ranges from 1-6 months, but there are perennial crops for which this period increases to 2 years (Table 1). Most flower crops, especially during 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 rest period in artificially created conditions and to awaken the embryo to growth and development, that is, to receive friendly seedlings by the given time.
Table 1. Dates of cold stratification of perennial crops
|Culture||Duration of stratification, days|
|Cherry plum||120-180, 130-150|
|Common cherry, chokeberry||150-180|
|Magonia, grapes, prince||120-140|
|Plum, turn, mountain ash||120-180, 150-180|
|Bird cherry, lilac, aconite, catchment, host, anemone||30-50|
Types of stratification
In practice, several types of stratification are used:
The need, duration and type of stratification, as a rule, is indicated on the package with seeds or in directories. Dry seeds purified from organic residues are placed on the stratification. Otherwise, in a humid environment, they can rot (apple trees, pears).
For seed perennial crops, in conditions of a clear separation into the 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. Seeds are placed in conditions with air temperature from 0 to +4 ºС and humidity 65-75%.
The duration of stratification in these conditions can be 1-6 months. It is used for pome seeds, stone fruits, some vegetable, flower and other crops. If the plants do not pass the cooling stage, they may not germinate in spring. That is, stratification imitates winter 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 residence at low temperatures can sprout without stratification. But in this case, the seedlings will be sparse and not friendly (sea buckthorn, honeysuckle, wild strawberry).
Thermal stratification differs from cold short duration. Usually, vegetable crops undergo thermal stratification. Dry seeds can be in suspended animation for a long time. But a rise in temperature 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 after a day or two the seeds are sprinkled, that is, seedlings of the embryos appear.
Combined stratification is applied to hard-like seeds and seeds of some crops in regions where, to increase germination, an imitation of changing seasons is needed. Usually these are perennial seeds with a thick dense peel (hawthorn, viburnum, snowberry, yew, apricot, plum).
Seeds of hawthorn and viburnum require a long (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 5-6 months in a cellar or cool place at a temperature of 0 .. + 5 ºС. For yew, some types of maple, a thermal period of stratification of 1.0-1.5 months is sufficient, and then the seeds are placed on a cold stratification.
This is the most complex form of multi-stage stratification of seeds. It consists of several low and high temperature cycles. So, the seeds of some types of pions, actinidia several times withstand alternately at high and low temperatures.
Primrose, aquilegia, aconite are repeatedly frozen. Before sowing for 5-7 days, their seeds are kept in water at room temperature +18 ºС during the day, and placed in the freezer of the refrigerator at night. In this case, seed germination is high and friendly.
List of some plants whose seeds require stratification
Fighter, or Aconite (Aconitum) Some types: Altai wrestler; The wrestler is tall; Bearded wrestler; The wrestler is an antidote; Hoodie wrestler. Two-stage stratification required:
- +20 .. + 25 ° С from 2 weeks to 3 months
- 0 .. + 5 ° С - 1-6 months
Anemone, or Anemone (Anemone) Some types: Anemone blue; Anemone nemorosa, or; White anemone; Anemone Altai. Two-stage stratification required:
- +18 .. + 20 ° С - 2-3 months
- +2 .. + 5 ° С - 3-4 months
Knapweed (Centaurea) Some types: Blue cornflower, or Field cornflower; Cornflower Fisher. Stratification is required at a temperature of +1 .. + 5 ° C - 1-2 months. Sowing can be done in open ground (April-May).
Clove (Dianthus) Some types: Carnation is sandy; Clove grass; Clove is magnificent. Sowing can be done in open ground (April-May).
Jeffersonia (Jeffersonia) Some species: Jeffersonia dubious, Jeffersonia bifolia. Two-stage stratification required:
- +8 .. + 10 ° С - 6 months
- 10/30 ° С * - 1 month
* Hereinafter in the list. X / Y ° C means that seeds should be kept at X ° C for 18 hours and at Y - 6 hours. This is the daily storage regime, that is, every day the seeds should be at X ° C. and at Y ° C.
Seeds quickly lose their germination. Sowing is carried out after harvest in mid-summer.
Delphinium, or Larkspur, or Spur (Delphinium) Stratification in sand is required at a temperature of +5 .. + 6 ° C from 2 weeks to 1 month. The optimum temperature for seed germination is +10 .. + 15 ° C
Bell (Campanula) Stratification in sand is required at a temperature of +1 .. + 5 ° C. Sowing in spring, seedlings at +10 .. + 15 ° С
Clematis, or Clematis (Clematis) Some species: Clematis Drummond, Clematis burning, Clematis whorled, Clematis ligustifolia. Two-stage stratification required:
- Stratification in sand or peat at 0 .. + 5 ° С - 2-3 months
- Germination 20/30 ° C * - 1-2 months
Seed germination is uneven.
Black cohosh smelly, or Klopogon ordinary (Actaea cimicifuga) Two-stage stratification required:
- 20 ° C - 2-3 months
- 4 ° C - 2-3 months
Germinate at 12 ° C.
Peonies (Paeonia) Two-stage stratification is required.
Peony dodging, or Peony extraordinary, or Peony Maryin root (Paeonia anomala).
- 18/30 ° С * - 1 month
- +5 .. + 7 ° С - 3.5 months
Milky-flowered peony (Paeonia lactiflora).
- 18/30 ° C * - 1.5 months
- +5 .. + 7 ° С - 2-3 months.
Leaf peony (Paeonia tenuifolia).
- 12/30 ° С * - 4 months
- 5 ° C - 1.5 months
Phlox (Phlox) Some species: Adorable Phlox, Douglas Phlox, Alox Phlox. Stratification in sand is required at +1 .. + 5 ° С - 2-4 months. The optimum temperature of seed germination is +5 .. + 12 ° C.
Liverwort, or coppice (Hepatatica) Two-stage stratification is required.
- +18 .. + 20 ° С - 1 month
- 12 ° C - 3.5 months
Seeds with a developed embryo germinate only at 12 ° C.
Attention: The above list is supplemented and adjusted. We are waiting for your comments and additions.
Methods of stratification at home
- Seeds laid for stratification are pre-disinfected. You can soak for 0.5 hours in a 0.5% solution of potassium permanganate. Then rinse in several water at room temperature. Dry, place in plastic bags, provide a detailed label indicating the type, grade and date of laying for stratification. Place the bags on the top 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 plastic bags are placed in a plastic container, tightly close the lid and fasten with tape. The prepared package is buried in the snow before melting. With the onset of heat, they are moved to the basement or to the lower shelf of the refrigerator before sowing.
Stratification in Cabbage Stalks
Ideal way for cold stratification at home.
Separate the stalks of late cabbage from the heads. We chop off the roots. In the resulting stump, remove the core. The resulting container is filled with seed material. Tightly close and fasten with adhesive tape the cover of the remains of the stump. We dig a “little egg” with seeds (like our grandfathers with gold coins) into the ground vertically into a hole deep in the bayonet of a shovel.
We fall asleep above. We set the number marker, and in the diary under its number we write information about the seeds, indicating the type and variety of culture, the time of laying and the end of stratification. In the spring, when the topsoil is heated to the temperature necessary for the crop, we dig a stalk with seeds and sow it in a prepared bed.
- Sanding. We prepare containers with a substrate, which can be large river washed sand, rotten sawdust, peat, moss. It is very important that the seeds are thoroughly washed from organic residues, sanitized and dried. Fill 2/3 of the capacity with a moist substrate. We lay out the prepared seeds and cover with the substrate on top. The substrate at the same time as hydration should be treated from a fungal infection with one of the biofungicides: trichodermin, phytosporin, alirin-B and others. Processing methods are usually indicated on the packaging. Capacities are closed with a lid, placed in a plastic bag to preserve moisture. Packed containers are placed on the bottom shelf of the refrigerator. The temperature should be within +3 .. + 4 ºС. With this storage method, at the end of the stratification period, the packets are transferred to conditions with reduced temperatures up to +1 ºС. In addition, the containers are periodically reviewed to monitor the condition of the seeds and, if necessary, moisten the substrate.
- Stratification in fabric rolls. On strips of natural fabric with a width of 10-12 cm and a length of 30-35 cm, we lay out a thin layer of moss or cotton wool. Gently spread the seeds. We bend the long sides of the fabric strip, which will cover the seeds from above, and roll up the roll. We bandage it, lower it into water to nourish moisture. Gently squeeze out excess water. We wrap the roll in a plastic bag and place it on the bottom shelf of the refrigerator. Each roll is provided with a label or number, and in the garden diary a detailed description (see above). During stratification, rolls are systematically checked for moisture. We control the condition of the seeds. If a fungal infection is detected, the seeds are washed, disinfected, dried and the entire process of laying for stratification on new pieces of material is repeated.
Some crops are sown and planted in the fall (winter sowing) in the soil, where they undergo stratification under natural conditions (winter garlic, green, some varieties of salads).
In addition to the described, there are other ways of stratification of seeds. Remember! Stratification will save you from the spring suffering associated with low seedlings or even their absence.