What Happened to My Germination?
Part 3 of 4
Let’s look at the major factors that a seed needs for germination. They are moisture, temperature, air, light, and soil.
Moisture – A dormant seed only contains about 10 – 15% moisture, so it must draw water from the soil that surrounds it. As the moisture is absorbed from the soil or seed starting media through the seed coat, enzymes are activated that convert the stored nutrition reserves and softens the seed shell, allowing oxygen to penetrate the seed coat, starting the process of growing. The moisture levels are critical at this early stage – they must remain constant for the sprouting process to continue and for the seedling to survive.
Uneven moisture levels can seriously delay the sprouting of a seed, and even a few minute’s lack of moisture as a seedling can kill it, as it has no method of storing water as a mature plant does. During the germination process, a seed needs much more moisture in the soil than when it has sprouted, so be aware and decrease the moisture levels as young seedlings emerge and mature.
Temperature – Germination will only occur in a specific range of maximum and minimum temperatures for each variety. Our Germination Guide lists these, along with the optimum temperature each one needs. The temperature we are talking about is the soil temperature, not the air temperature above the seed tray or garden row. Slightly cooler temperatures can double or triple the time needed for germination – even as little as 5°F cooler can be the difference between a 7 day or a 14-day seedling emergence!
When starting seeds inside, a bottom heat such as a seed sprouting heating mat on a thermostat is invaluable. In the garden, double-check the soil temperature with a soil thermometer before spending the time and effort in carefully planting your seeds and being disappointed later.
Air – Seed germination requires large amounts of oxygen to activate the metabolic process of converting the stored nutrients into energy. The oxygen that is dissolved in water and from the air contained in the soil is used. If soil conditions are too wet, an anaerobic condition can be created and seeds may not be able to germinate due to lack of oxygen.
Light – Some seeds need light for germination, while some other seed varieties are hindered by light. Most wild species of flowers and herbs need darkness for germination and should be planted slightly deeper in the soil while most modern vegetable crops prefer light or are not affected by it, and are planted shallowly to allow small amounts of light to filter through the soil.
Soil – It is the medium for successful seed germination. In the germination tray, it may be absorbent paper (blotting paper, towel, or tissue paper), soil, sand, or a mixed media made specifically for seed germination. The substratum absorbs water and supplies it to the germinating seeds. It should be free from toxic substances and should not act as a medium for the growth of microorganisms. It needs to be loose, allowing the moisture to easily reach the seed and for the seed to move as it grows without spending lots of energy in moving the soil to reach the surface.
A few things to consider
1. Keep seed packets in a cool dry place. Do not store in your garage, potting shed or near a heat source such as a heater or appliance.
2. Review the seed packet’s individual instructions and develop a planting schedule based on your local weather and growing season.
3. Re-seal any seed packets that you are starting indoors, such as pepper, eggplant, and tomatoes. This will allow you to start more seeds later if you want to stagger your plantings, etc.
4. It may be better to over plant and then share plant starts with neighbor and friends, than to underplant and be caught short.
5. Download the Terroir Seeds Garden Journal to get a jump start on tracking your garden this year.
An excerpt from “What Happened to my Seed Germination?“, courtesy of Terroir Seeds.