Plant seeds grown in natural conditions, after their maturation and before germination, are exposed to many factors, including temperature (change of seasons), mechanical (impact and friction against the ground under the influence of wind loads), atmospheric (rain, snow), chemical (minerals and other active substances in the soil), and biological (microorganisms, and sometimes the intestinal tract of birds or animals). Nature has provided for all these dangers, so plant embryos are enclosed in a stronger shell that can protect them from adverse conditions.
But what if ripe seeds are immediately collected and stored until planting in a dry, warm and absolutely safe place? Is this good for future plants? After all, the seeds are in a state of complete rest and comfort, and their development requires awakening. How to wake them up?
There are several ways to stimulate seed germination. The simplest of them and very soft, gentle is impaction. It is intended for minor damage to the integrity of the seed coat in order to increase the possibility of getting more moisture to the embryos. Impaction at home is carried out using a glass or plastic container with a lid. Seeds are placed inside it. For greater efficiency, you can pour a little sand there. Then it is enough to shake it for some time. During the impact of seeds against each other and friction with sand, the seed coat is damaged, but the integrity of the embryos is completely preserved. Impaction is mainly used to stimulate the seeds of legumes (beans, soybeans, alfalfa, peas, clover, etc.)
But this method will not give a noticeable effect when applied to seeds with a strong and thick shell (usually all stone fruits). In this case, scarification is used (translated from Latin - to scratch, cut). It consists of a more severe destruction of the hard seed coat and stimulates the rapid germination of the embryos. A distinction is made between mechanical, chemical and thermal scarification.
In the first case, particularly strong seeds are carefully filed with a file, facilitating the access of moisture and air inside them, thereby ensuring the accelerated emergence of sprouts. Alternatively, a sharp knife, sandpaper, or a whetstone are used for this purpose. Or the seed coats are ground until cracks form in them using sand or stones.
Chemical scarification to achieve the same goal (destruction of the seed coat) involves the use of certain acids as a destroyer (2 - 3% sulfuric or hydrochloric acid) until the shell softens. This method is almost never used due to the increased degree of danger to both humans and future plants (in case of overdose).
To carry out thermal scarification, it is necessary to place the seeds to be treated in a permeable bag and alternately dip it for a second or two in a container with hot water, and then in cold water. Repeat the procedure three times. The greater the temperature difference, the better the result. Those seeds whose shell bursts are ready for planting. The rest can be processed until the same result is obtained.
Stratification is another method of stimulating the germination of hard-to-germinate seeds, and it consists of storing them at low temperatures for a long period (from several weeks to a year) in damp, disinfected sand or peat mixture.
In nature, seeds sown in the pre-winter period undergo natural stratification in the soil under the snow, and by spring they are ready to germinate. The same seeds that were stored in the warmth all winter are subjected to artificial stratification to stimulate germination.
Initially, the seeds are soaked in water (the water is constantly changed) for two days (for pome fruits) or for 5-7 days (for stone fruits). Then they are treated with a disinfectant (potassium permanganate solution) to prevent damage by various diseases. Calcined sand or peat, moss is poured into a low treated container as a substrate, it is well moistened (humidity should be up to 60%), then the seeds are laid out in the next layer (three parts of the substrate are needed for one part of the seeds). They are sprinkled with a small layer of wet substrate on top, the container is covered with a film and transferred to a room with a temperature of 2° to 5°C. The seeds are periodically inspected, the mixture is shaken and moistened as needed. As soon as tiny sprouts appear, the container is covered with a lid and taken out into the cold (up to 0 ° C). Before planting, the seeds are kept in a warm room for 5 to 10 days, in no case allowing them to dry out.
The "home" version of stratification is carried out according to a simplified scheme. Clean, washed and calcined coarse-grained sand is used as a substrate, but you can also use a regular peat mixture for indoor plants, having previously calcined it. In a small container (plastic container, flower pot), pour a small layer of well-moistened peat mixture, and then seeds, and so alternate them layer by layer. We pack the container in a regular plastic bag with ventilation holes made in it and place it on the bottom shelf of the refrigerator. As the sowing season approaches, we move the container with seeds to a warm and bright place. And as the seeds germinate, we gradually increase the amount of lighting.
The use of all these stimulating methods allows you to significantly increase the germination of seeds, their growth and development, which is important for getting a good harvest in our garden plots.