The title ‘Special treatment to seeds for germination’ may get many people’s eyebrows rising. After all, most of the annuals as well as perennial seeds germinate in normal weather condition without any excessive effort from the grower. However, some of the seeds have evolved over the centuries to need certain specific conditions to start their growth cycle like the heat and chemical changes resulting from a forest fire. Some seeds need total darkness to germinate, and others need total light, some have a hard, impermeable seed coat, and some seeds die if they dry out. Depending on the species of plants require different weather condition, pH levels, growth media, and other physical conditions.
Let us study the different basic treatments like scarification, soaking, stratification, chilling, moisture maintenance, and storage conditions.
1. Scarification – Some of the seeds have hard seed coats and therefore they cannot absorb moisture. They have the ability to store water very well for over a long period, however, they need to have their coats broken, scratched or mechanically altered so that water can interact with the seed to trigger germination. This process is called scarification, and it can be done with the help of a knife, sandpaper or a file. Keep in mind that scarification needs to be performed with a lot of care, otherwise if seeds get injured in the process, it can allow pathogens to attack the seed and curb the process of germination altogether.
Seeds of the Fabaceaee, Malvaceae, Cannaceae, Geraniaceae, Convolvulaceae, Solnaceae, Chenopodiacae and Aeacaceae families to have hard seed coats. Certain seeds like Pelargonium are already mechanically scarified so that gardeners can directly sow them in soil without having to actually perform the scarification of seeds. However, readymade scarified seeds cannot be stored for a long time. Some seed are too small to be easily handled and mechanically scarified; these should be soaked to soften their hard seed coat.
2. Soaking – Soaking triggers seed germination. Soaking actually reduces time required for germination. Some seeds have a hard seed coat that is softened by soaking. In case of certain seeds, chemical inhibitors have to be leached out to start germination. Soaking for 24 hours is usually sufficient. If more time is needed for a particular plant, it is advised to change the water once a day to provide needed aeration and to prevent the building up of microorganisms.
Place the seeds in a container and add 5-6 times their volume of hot (190 degrees F) water. Never boil seed in water, as this will injure and even kill them. Plant the seeds immediately after soaking, and do not let them dry out before sowing.
3. Stratification – Perennial seeds and woody plant seeds have an immature or dormant embryo and germination in such seeds has to be triggered by altering external physical factors. Some plants, such as Lettuce and Delphinium, become dormant when exposed to temperatures over 75 degrees F. For a prolonged period; seeds of these plants must be chilled to induce germination.
Seeds can be stratified using couple of methods depending upon their size and convenience of grower. You may go ahead and plant your seed in a chosen container filled with moistened medium, place the whole container in a plastic bag and put it in the refrigerator (for temperatures around 40° F.) or freezer (for temperatures of 32° F. or lower) for the requisite time.