Sometimes, seeds refuse to germinate – despite your best efforts. There are several reasons that this can happen – and some might be a little surprising!
So, what should you do if your seeds do not germinate? If seeds do not germinate, try using newer seeds – and plant them at the proper depth! Provide seeds with proper soil aeration, moisture, and temperature. Many seeds germinate best at 70 to 75 Fahrenheit (21 to 24 Celsius) – but each type of seed has an ideal soil temperature range for germination.
A good rule is to plant seeds at a depth that is twice their diameter (so a 1 inch seed is planted at a depth of 2 inches). Remember that some seeds (like lettuce) need light to germinate!)
In this article, we’ll talk about the factors that can affect seed germination and how each of them might be holding you back from getting your seeds to sprout.
Let’s get started.
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What To Do If Seeds Do Not Germinate
In the ideal conditions, seeds germinate much faster – and you should also get a higher germination rate (that is, the percentage of planted seeds that sprout).
If your seeds do not germinate after the times indicated in the app, the problem is likely one of the 5 factors below:
There is no “one size fits all” answer to the question of why seeds don’t germinate.
For example, lettuce seeds like somewhat cooler soil for germination (60 to 75 Fahrenheit is their ideal range). On the other hand, squash seeds like warmer soil for germination (85 to 95 Fahrenheit is their ideal range)
Some seeds (like corn) should be planted deep, while others (like celery) should be just on the surface of the soil. Some seeds (like arugula) last a long time, and others (like spinach) only last a year before their germination rate declines rapidly.
Below, we’ll take a closer look at each of the 5 seed germination factors so you can make sure that everything is on point.
1. Maintain Correct Soil Temperature
Soil temperature is a key factor in seed germination. At the right soil temperature, seeds will germinate faster – with a higher germination rate.
If the soil temperature is too low or too high, seeds take much longer to germinate (if they ever do!) So, it makes sense to get soil temperature right so you can save yourself time (and wasted seeds).
For most flower and vegetable seeds, a soil temperature of 70 to 75 degrees Fahrenheit (21 to 24 degrees Celsius) will work just fine.
Most seeds can still germinate in soil that is outside of this range – it just takes a little longer. For example, squash can take 11 or more days to germinate in soil that is 70 to 75 Fahrenheit (as opposed to 5 to 10 days in soil at 85 to 95 Fahrenheit).
Maintain the correct soil temperature for your seeds and they will reward you with faster germination (as long as the other factors like moisture, etc. are right – more on that later).
You can get a visual of the way soil temperature changes time to seed germination with my app! (preview below)
To give one example, peas take about 6 to 7 days (around 1 week) to sprout at their ideal soil temperature range of 65 to 75 Fahrenheit (18 to 24 Celsius). On the other hand, peas may take as much as 36 days (over 5 weeks!) to sprout at a soil temperature of 40 Fahrenheit (4 Celsius).
A good soil thermometer will tell you the exact soil temperature, which you can use to make adjustments as needed. A heat mat is one way to keep soil warmer for seeds, but there are other methods too.
(You can also learn about lots of ways to keep soil warm for seeds here.)
After you get your soil to the correct temperature, the next thing to do is to consider soil moisture.
2. Provide Proper Soil Moisture
Soil moisture is another important factor in seed germination. At the right soil moisture, seeds will have a higher germination rate.
Seeds also need air to germinate (more on that later). This means soil should be damp, but not soaked.
If the soil is too wet, seeds will not get enough air – and they will be subject to rot or damping off. If the soil is too dry, seeds will not germinate.
One method I like to use for keeping soil moist is a spray bottle (plant mister). This simple device makes it way easier water a seed tray container, with less chance of over watering (which tends to wash away soil or seeds, or drowns them).
Another way to keep soil moist is to use the bottom water method for your seed trays. This method involves placing the seed tray inside a larger container of water.
As long as the seed tray has holes in the bottom, the soil will slowly soak up moisture from below. It will work against the natural force of gravity to absorb the water your seeds need to germinate.
Whether you water with a spray bottle, bottom watering, a cup, or any other method, a humidity dome can still help you out. A humidity dome is kind of like a mini greenhouse, but it is usually made of clear plastic instead of glass.
The purpose is to retain moisture in soil and air beneath the dome. This is really helpful if you have to deal with dry air in your house. Remember to take off the dome after your seedlings sprout.
A good seed starting mix is also helpful if you want to maintain proper soil moisture for seed germination.
Seed starting mix is soilless and fine (no big clumps), and it usually lacks nutrients (you need to add fertilizer later, after your seedlings sprout). Using topsoil from the garden is not the best idea – you might introduce pathogens that grow well in a warm, humid environment and kill your seeds.
Seed starting mix often has some combination of perlite, vermiculite, peat moss, coconut fiber, and possibly some sand or sterile compost.
3. Ensure Good Soil Aeration
Sometimes, it is easy to forget that seeds are living things. They need warmth, water, and even air (yes, they “breathe” in a sense!)
So, it follows that seeds need good soil aeration in order to survive and germinate. There are a couple of ways that seeds end up with a lack of air.
One way is when the soil is too wet. The ideal soil for seeds contains some water and some air. Soggy, soaked soil has too much water – and not enough space for air. This “drowns” the seeds and keeps them from germinating.
Another way is when soil becomes compacted. Normally, there is space between soil particles for air and water. When soil gets pressed down (by walking on it, or putting heavy loads on it), the soil particles get pressed close together. This leaves less room for air.
So, don’t over water your seeds (see the spray bottle or bottom watering ideas above), and don’t push down too hard on the soil!
4. Plant Seeds At The Proper Depth
Planting depth is sometimes overlooked, but it is another important factor for seed germination. If you plant seeds too deep, they might not have enough energy to reach the surface after they sprout. If you plant seeds too shallow, you will often see poor germination rates.
Planting seeds at the right depth increases germination rate and helps plants to sprout faster. The proper depth to sow seeds varies by plant type, but one rule you can follow is: aim to plant the seed at a depth that is twice its diameter.
For example, a seed that has a diameter of 1/4-inch is planted 1/2 inch deep. A 1 inch seed is planted at a depth of 2 inches. The smallest seeds should just barely be covered with soil.
Remember that certain types of seeds (such as celery, dill, lettuce, or petunias) need some sunlight if they are to germinate. So, it’s best to lightly press those seeds into the top layer of soil (maybe sprinkle a dusting of peat moss lightly over them).
You can find out about what types of seeds need light to germinate here.
5. Use Newer Seeds
Are all seeds equal, regardless of age? Well, no – not exactly. After some time passes, seeds are less likely to ever germinate – and some seeds “expire” much faster than others.
Sowing newer seeds might not reduce up the time germination, but it’s one way to get higher germination rates – and avoid wasting your time on seeds that will never sprout.
If you plant seed that is too old (expired), you will get lower (or possibly zero!) germination rates. Some seeds last a long time, while other expire in short order.
For instance: lettuce, onion, spinach, and some herb seeds will only last about a year before their germination rate declines a lot. On the other hand, seeds like cauliflower, eggplant, and pumpkin will last around 4 years before their germination rates decrease considerably.
Conclusion
Now you know what to do if your seeds do not germinate – keep at it, and don’t give up. Sometimes, seeds take a little longer to sprout than you thought they would.
I hope you found this article helpful. If so, please share it with someone who can use the information.
You can learn how to save seeds from your garden here.
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~Jonathon