Did you know that your seeds may have an expiry date? Seeds are living organisms (albeit in a dormant state), waiting for the right conditions to break their dormancy and start germinating and growing. Different seeds respond to different conditions, sometimes waiting decades before opening up and continuing the plant’s life cycle. Here are some of the main factors that can influence seeds
Seeds are sensitive to temperature changes and the exact length of each temperature fluctuation can influence the seeds. Many seeds in the Northern Hemisphere need a cold winter of a certain length before growing
In order to prolong the lifespan of the seed, many seeds are equipped with a hard outer coating. To make it easier for the plants to open up, scarifying or roughing up the outer coating of the seed can help. Some gardeners use sandpaper to manually scarify their seeds and improve germination or a knife to help the seed germinate and break through the outer coating.
Seeds need moisture before they germinate. You’ll note that seeds that you purchase or save need to be dried out, with most dormant seeds containing 10-15% water. When the seeds absorb moisture, they become active. At the same time, the seed coat is softened (making it easier to rupture) and the enzymes within the seed become active and start to swell and grow.
Dormant seeds have a very low respiration rate so very little oxygen is required. However, when germination is about to take place, much larger quantities of oxygen are needed both from air and when dissolved in water.
Some seeds need fire before they can germinate while others need cold dormant periods before their are ready. Most seeds however, need a moderate temperature ranges. with optimal temperatures between 18-24C. Above or below certain temperatures can inhibit germination.
Different seeds will require different light intensities with some needing light to germinate while others being inhibited by light. By planting seeds deep, light can be shut out. By planting seed shallow, light can still filter through the soil.
Seeds naturally degrade over time. The longer they go without germinating, energy reserves are used up and some seeds are incapable of supporting growth after extended periods of time.