The number one reason customers decide to purchase their seedlings through us (order at www.livingtowerseedlings.com) is because theirs fail to germinate. When you are growing in the ground and you scatter a number on the soil you barely notice if they don’t all sprout. It’s very different seeding for a Tower Garden. Most of the crops (with the exception of herbs, lettuce mixes and some other greens) require just one seed in each rockwool cube so you certainly notice when nothing sprouts!
What affects whether a seed germinates?
There are a number of external factors that determine whether a seed successfully germinates. Water, air, temperature and in some cases light. Different plants require different variables for successful seed germination.
Water – Water or moisture is required for seed germination as dormant seeds are extremely dry. The seed has to absorb water in order to become active. The embryo then begins to swell. The softened seed coat splits open as the seed grows too big for its encasement and germination has commenced. Photosynthesis does not begin until the true leaves are developed. At this point in development the seedling is still surviving on its own food reserves!
Air – When a seed is dormant it’s respiratory rate is very low and oxygen is required in very small quantities. Oxygen is needed in much larger quantities for germination to occur. The seeds obtain oxygen that is dissolved in water and from the air contained in the soil (or in our case rockwool). If soil conditions are too wet, an anaerobic condition persists, and seeds may not be able to germinate. Do not leave your rockwool totally submerged in water! Just 1/4 inch of water in the bottom of the container in the morning is plenty. You could even water from above, when needed, throughout the day.
Temperature – The temperature that germination occurs can vary greatly between different crop types. The optimum for most crops is between 65-75°F, but exceptions do apply. For example lettuce germinates best at 65°F and can be inhibited at temperatures over 68°F while peppers and eggplants prefer warmer temperatures around 80°F and will not germinate well at cooler temperatures. If your soil (or in our case rockwool) is too cold or too hot, your seeds may not sprout. It is because of this that you will not find us growing Spinach seedlings during the summer months. Check your seed packet to find the best temperature needed for your seeds.
Light – Some seeds need light for germination, while some seeds germination is hindered by light. 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 (or vermiculite for us Tower Garden growers).
So why didn’t my seed germinate?
If none of the seeds germinated then it is more than likely too cold, too hot, too much or too little water or the seed is simply dead. When germination is poor it is most likely a degradation of seed quality, and the seed has begun to die. Seed death begins as soon as the seed is mature and viable. In general seeds hold high germination rates for 2-3 years falling no less than the 80% range. Once seeds hit about 75% germination they start to loose the ability to germinate quickly.
Outdated seeds will not germinate properly. Most seeds have a shelf life of only one to two years if kept in a cool dry place over winter. When planting seeds, be sure to use the freshest seeds available to you. The best way to store leftover seeds is in an air tight glass jar in the refrigerator or freezer with a little bit of powdered milk wrapped in a paper towel to absorb the excess moisture. Seeds that have been in the garage or shed all summer will, more than likely, fail to germinate.