Why Didn’t My Seeds Germinate? Tips for Future Success

I hope that you will find your windowsills and your polytunnel, like mine, filling up as the spring season gets into full swing and seeds germinate.

Unfortunately, as new gardeners quickly find, not everything in gardening goes entirely to plan. If you planted plenty of seeds, only to be confused by poor germination rates or seeds failing to germinate altogether, you may be wondering why.

Below, I will try to give you some things to look into to find an answer to your question. Understanding what went wrong should help you avoid such issues in the future, and go on to grow plenty of your own crops and other plants from seed at home. 

Temperature Problems

One important thing when it comes to seed germination are the temperatures of the soil or growing medium. If the conditions were too cold, or too hot for the seeds in question then you may experience patchy germination. The seeds may even fail to germinate altogether. 

If you are sowing seeds indoors or under cover, you must pay close attention to the temperatures of the environment. 

A sunny windowsill may be warm during the day, but may become chilly when temperatures fall in unheated spaces overnight. The temperatures, even indoors, may not always be warm enough for warm season crops, which require warmer conditions. 

For certain crops, you may require a heated propagator to provide the temperatures for seed sowing, especially when sowing early in the year. 

However, if you are using a propagator, temperatures may become too warm for certain seeds to germinate well. And it is important to note that some seeds require a prior period of cold stratification in order to germinate successfully. 

If you are direct sowing outdoors, it is important to time things correctly. Sow too early, and a late cold snap could lead to poor germination, or even mean no seedlings emerge at all. 

Understanding the temperature ranges in which different seeds will germinate is crucial to successful germination. Temperature will have a bearing on cellular metabolism and growth rates. Seeds will generally germinate within a certain temperature range. They will not germinate at all outwith this temperature range, and at the extremities of the temperature range, germination rates may be significantly reduced. 

Water Problems

Water is usually required for seed germination. Mature seeds are usually very dry, and need to absorb and take on significant amounts of water before cellular metabolism and growth can resume. Water imbibation activates hydrolytic enzymes, that begin to break down stored food resources into chemicals that can be used metabolically. The seed coating will break down and the seedling will emerge. 

You may have provided too much water to the seeds as you sowed them. Or you may have neglected to keep the soil moist. 

However, water problems might also be related to drainage issues. If the water you provide for seedlings cannot drain away, waterlogging can occur. Waterlogging can lead to compaction of the medium (see below) and can also increase the likelihood of a problem like damping off, or other fungal issues taking hold. 

Lack of Oxygen

Until a seedling grows leaves, aerobic respiration provides its main source of energy. Oxygen is needed by a germinating seed for metabolism. Oxygen needs are very much tied in with water requirements. Some seeds have coatings that need to be broken down before water and oxygen can be absorbed from the environment. 

As mentioned above, watering too much, or not providing sufficiently free drainage for water to flow away can cause compaction. In waterlogged conditions, the air within the medium will be reduced, leading to anaerobic conditions. This can mean that seeds won’t get the oxygen they need. 

Choosing the wrong growing medium can also lead to a lack of oxygen. So it is important to choose a light and friable potting mix, or seed sowing compost, when sowing your seeds. 

Seeds may also simply fail to get enough oxygen if they have been buried too deeply. Make sure you understand and adhere to the right depth for seed sowing for the plants you are trying to grow. 

Lack Of Light

Some seeds must be sown close to the surface, or even on the surface, because they not only require oxygen but also need light to germinate. Burying these seeds too deeply can often mean that they will not germinate at all. Again, make sure you have read instructions for the particular seeds you sow and the plants you wish to grow. 

Seeds Were Not Viable

If you are certain that you did everything right and provided the right environmental conditions for your seeds, and yet they still didn’t germinate, sadly, the seeds may simply no longer be viable. 

First of all, seeds might not be viable if they were stored incorrectly. If seeds are stored in unsuitable conditions – either en route to you, or in your home – where the temperatures are too high, for example, they may have been damaged and may no longer be able to grow into plants. 

It is also important to note that seeds lose viability over a certain period of time. They will not typically be good to sow indefinitely. Seeds will only be viable for a certain length of time, and some will be viable for less time than others. Your seeds that failed to germinate may simply have been too old. 

Seeds Have Been Eaten

If you are still mystified about the lack of germination and have ruled out all of the above, there is one more thing to consider. Your seeds and the environmental conditions may have been fine but seeds may have been eaten before they had a chance to germinate. Of course, this is more likely if you have direct sown seeds into your garden. Birds, mice and other pests may have gobbled up the seeds before they started growing. 

You may not always be able to pinpoint the exact reason why seeds didn’t germinate. But by working through the possibilities above, you may be able to make sure that you meet with more success in future.