Breaking seed dormancy

Seeds remain in a state of dormancy (a temporary state of inactivity in growth) until environmental conditions are ideal for germination. Some of them will germinate on their own as soon as the climatic conditions are right. Others will need a helping hand to germinate even though the optimal conditions are met: this is called dormancy breaking. There are different techniques that aim, as the name suggests, to reduce seed dormancy and reproduce the appropriate conditions in their natural environment. What is dormancy breaking? There are two types: Breaking seed coat dormancy softens or damages the seed coat surrounding the seed. This coat is a protective layer that prevents the seed from deteriorating over time. This envelope protects the seed from water and light and therefore prevents germination from occurring. In some cases, it may also contain substances that inhibit germination. The breaking of embryonic dormancy is adapted to the type of dormancy. It reproduces climatic conditions and allows the seed to be forced to germinate in an unfavorable season. What are the different methods for breaking dormancy? The breaking of seed coat dormancy can be done in 3 different ways: • By acidity. In nature, fruits consumed by animals are then digested. The seeds then come out of dormancy naturally thanks to the acidity of the digestive juices which destroy the seed coat. To imitate this process, it is possible to soak the seeds in vinegar for about 12 hours. Examples: cranberries, bilberries, Saskatoon berries, strawberry trees, sea buckthorn. • By scarification. The goal is to slightly damage the different protective layers that envelop the seed. For the smallest seeds, it is possible to mix and knead the seeds in a little sand. For larger and more malleable seeds, sandpaper or a cutter can be used. Examples: New Zealand spinach, acacias, sophoras, albizias. • By water. The seed coat will soften on contact with water to allow the seed to germinate. To do this, it is advisable to soak the seeds for 12 to 24 hours in lukewarm water before sowing. Examples: beans, broad beans, peas. There are 4 ways to break embryonic dormancy: • By light. Some seeds require long exposure to the sun. It is the action of red light rays that stimulates the photoreceptor pigment (phytochrome) in the seed coat and triggers germination. This process requires suitable lighting. Examples: cranberries, cranberries, Saskatoon berries, strawberry trees, sea buckthorn. • By cold (vernalization). This method consists of exposing the seed to a temperature variation over a set period of time so that the breaking of dormancy can be triggered. To do this, we simulate the winter season to force the seed to germinate in the desired season. This very common technique can be natural by exposing the seedlings to the cold in winter or artificial by temporarily storing these seed packets in a refrigerator. Examples: strawberries, mertensias, tuberous chervil, physalis, fruit trees. • By fire. This technique remains rare but very effective. The plant then benefits from a natural fertilizer: ash. It can be natural following forest fires and fires, or artificial by burning the seeds in a metal basin filled with potting soil. They are then covered with 7 to 8 mm of potting soil with a light mulch of twigs on top. After burning everything, the seeds are left and watered for several weeks under this layer. Examples: conifers. Note: a single species can be subject to several different stratifications. Why break the dormancy of certain seeds? Stratification allows for more uniform and faster seed emergence. For some species, breaking dormancy is strongly recommended (example: tuberous chervil), for others it is not necessary (examples: basil and tomato).