If you are planting (or have already planted) sunflower seeds, you are probably wondering just how long they take to sprout. You may also be curious about how you can speed up the seed germination process.
So, how long do sunflower seeds take to germinate? Sunflower seeds take 4 to 11 days to germinate, depending on soil conditions (temperature and moisture are the most important factors). To speed up germination, plant sunflower seeds 1 to 1.5 inches deep in warm soil (70 to 78 degrees Fahrenheit) that is damp, but not soaked.
You can see how soil temperature affects seed germination with this app I made!
Of course, you can germinate sunflower seeds indoors and transplant them outside later. However, sunflower seeds can be direct sown, so it might be less work to germinate sunflower seeds directly in the soil outdoors where they will grow.
In this article, we’ll take a closer look at some of the factors that affect how long sunflower seeds take to germinate. We’ll also see how we can optimize these factors to encourage faster seed germination and reduce sunflower germination time.
Let’s get started.
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How Long Do Sunflower Seeds Take To Germinate?
Sunflower seeds normally take between 4 and 11 days to germinate under ideal conditions. However, sunflower germination time can vary a lot, depending on soil temperature and other key factors.
According to the Iowa State University Extension, sunflower seeds can take as little as 4 days to germinate when planted an inch deep in warm soil (meaning in the 70’s Fahrenheit).
On the other hand, Purdue University suggests that sunflower seeds can take up to 11 days to germinate (more likely in cooler soil).
It will all depend on the various factors that affect time to seed germination – let’s get into some of those now!
What Factors Affect Sunflower Seed Germination?
The time a sunflower seed takes to germinate depends on several important factors, such as:
- Soil Temperature – soil that is too cold or too hot will both slow or stop germination.
- Soil Moisture/Humidity– soil that is too wet causes rot or mold, while soil that is too dry prevents germination (the same goes for dry air, which causes faster evaporation of water from the soil).
- Air Circulation – seeds need air to “breathe”, and soil that is too wet prevents this from happening.
- Planting Depth – seeds planted too deep (or too shallow) will have low germination rates.
Let’s dive into more detail on each of these factors, starting with soil temperature.
Soil Temperature For Sunflower Seeds
According to the North Dakota State University, the minimum temperature for sunflower seed germination is 50 degrees Fahrenheit (10 degrees Celsius). Any colder than that and you may get low germination rates, delayed germination, or no germination at all!
In fact, the University of Georgia Extension suggests waiting until soil temperatures are at least 60 degrees Fahrenheit (16 degrees Celsius) before planting sunflower seeds (just to be safe).
If the soil is too cold, you will see low germination rates – that is, if you can get any seeds at all to germinate! This is nature’s way of protecting sunflower seeds from sprouting at a time when they will be unable to survive (that is, in the middle of winter!)
(You can learn about germination rates and how to do a seed viability test here).
***Note: You can find the germination rate on the seed packet itself. For example, if the germination rate is 95%, then you would expect 95 seeds to sprout out of every 100 seeds that you planted, or about 19 out of every 20.***
According to Purdue University, the maximum temperature for sunflower seed germination is 91 degrees Fahrenheit (32.8 degrees Celsius). If the soil is any warmer than this, germination rates will decrease.
Combined with high humidity, high temperatures encourage the growth of mold, which is another threat to your plants.
The ideal (optimal) temperature for sunflower seed germination is between 70 and 78 degrees Fahrenheit (21.1 to 25.6 degrees Celsius).
Keep in mind that these numbers refer to soil temperature, not air temperature. If you want to find out the soil temperature, use a probe-type thermometer to check.
If the thermometer reads a temperature that is too low, then you have some options. One is to wait to sow seeds until the sun warms up the soil.
To speed up this process, clear away any debris (such as leaves or grass clippings) from the soil surface. Also, make sure to choose a location for planting that gets plenty of sun, so that it can warm up the soil faster.
You can even lay down a layer of black plastic on the soil. This will absorb more energy from the sun and trap more heat underneath.
If you are worried about a short growing season, you can also use a cloche (a plastic or glass cover) to trap some heat and warm up the air and soil near your sunflower seeds.
A cloche can be made from a plastic water bottle, and will keep seeds or seedlings warmer than the surrounding air, especially on sunny days.
A cloche can be made from a plastic water bottle to trap heat and moisture in a small area to help seeds germinate faster.
(You can learn more about how to keep seeds warm in this article).
The table below shows a recap of minimum, ideal, and maximum temperatures for sunflower seed germination.
| Soil Temp | Temp (degrees F) | Temp (degrees C) |
|---|---|---|
| Min | 50 | 10 |
| Ideal | 70 to 78 | 21 to 26 |
| Max | 91 | 33 |
maximum temperatures for
sunflower seed germination.
Soil Moisture/Humidity For Sunflower Seeds
Soil moisture or humidity is another important factor to consider when germinating sunflower seeds. When soil dries out for too long, there is a chance the seeds will die.
If the air is too dry, then the soil will dry out faster, and the seeds will have trouble germinating.
If the air is too humid, then the soil will stay too wet, especially if you over water. This can lead to damping off, which occurs when mold or other pathogens affect seeds or seedlings.
Damping off is more likely with high humidity levels, in moist soil, and at cooler temperatures.
Image courtesy of:
INAKAvillage211 from:
https://commons.
wikimedia.org/wiki/File:
Pinus_taeda_seedling_
damping_off_(cropped).jpg
(For more information, check out this article on damping off from Wikipedia).
If you find that you have trouble soil moisture and humidity, you do have some options. One is to use a cloche (mentioned earlier).
When sealed, a cloche traps moisture in the air and soil. That way, seeds have the humid environment they need for proper germinate.
A cloche will help your seeds to germinate faster, increase germination rates, and cut down on the time and effort needed to keep soil moist.
You can also use a humidity dome – you can buy one or make your own (learn more here).
Another option is a cold frame (which is sort of like a mini greenhouse).
Air Circulation For Sunflower Seeds
Seeds need air, just like seedlings and established plants. If the soil is too wet and there is too little air circulation, it will spell death for your seeds before they even have a chance to get started.
To keep your seeds from suffocating due to lack of air, there are two things you can do.
First, keep the soil moist, but not wet. Do not over water the soil, and consider using a cloche to help you to get the right moisture level.
Second, keep the soil loose. Do not compact the soil by pushing down on it either before or after planting your seeds.
When there is more space between soil particles, there is more space for air and water, both of which are necessary for seed germination.
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Planting Depth For Sunflower Seeds
Sunflower seeds should be planted 1 to 2 inches deep for ideal germination. If you plant the seeds too deep, they will fail to germinate or never reach the soil surface.
You can learn more about proper planting depth for seeds in my article here.
How Do I Make My Sunflower Seeds Germinate Faster?
If you want to make your sunflower seeds germinate faster, there are several important actions you can take.
First, protect your seeds from extreme heat and cold. As mentioned earlier, temperature is one of the most important factors that affects seed germination.
If it is too cold to plant seeds outside, then start your seeds indoors (or in a greenhouse outdoors). This gives you a head start on the growing season, and it also minimizes the danger of late spring frosts killing your seedlings.
This is especially helpful if you live in an area with a short growing season (such as northern Vermont).
Second, ensure that the soil is damp (not wet!) and the air is humid. Seeds will not germinate if there is not enough moisture in the soil and air. Consider a cloche to help with maintaining humidity.
You can also use a spray bottle to keep soil just damp enough, but not too wet.
Third, make sure that the soil has enough air circulation. This means that you should avoid compacted soil both before and after planting. It also means that you should avoid over watering your soil.
Fourth, remember that sunflower seeds do not need light to germinate. It is more important to have them in a warm place than in a bright place before germination. If you start sunflower seeds indoors, give the seedlings bright overhead lights (grow lights) after germination.
Fifth, make sure to plant your sunflower seeds according to the proper depth and spacing. Sunflower seeds should be planted at a depth of 1 to 2 inches (2.5 to 5.1 centimeters). If planting in rows, space plants 6 inches apart (2 per foot).
When the first true leaves appear, thin the seedlings (1 plant per 2 feet) to prevent competition between plants.
For more information, check out this article on sunflowers from the Burpee website.
Finally, you can scarify (scratch the surface) of your seeds in order to encourage germination. This can speed up germination and also increase germination rate (the percentage of seeds that sprout).
For more information, check out this article on seeds and seedlings from the Penn State University Extension.
Should Sunflower Seeds Be Soaked Before Planting?
You can soak your sunflower seeds before planting to encourage faster germination. Put them in clean water and let them sit for up to 24 hours before planting.
However, this type of soaking is not required. As long as the growing medium is warm and damp enough, your sunflower seeds should germinate well.
Can You Germinate Sunflower Seeds In A Paper Towel?
You can germinate sunflower seeds in a paper towel. The paper towel holds moisture and allows the seeds to breathe, serving as an alternative growing medium to soil.
To germinate sunflower seeds on a paper towel, wet the paper towel until it is damp (not soaking wet). Then, lay out the sunflower seeds so that they are separated (not touching).
Be sure to keep the paper towel and seeds in a warm place. This encourages faster germination and higher germination rates.
The only drawback of this method is that you will need to transplant the sprouted seeds into soil by hand, since they will soon need nutrients from the soil to grow and establish stronger roots. Be gentle when handling the tiny sprouted seedlings!
Germinating sunflower seeds in a paper towel may be helpful if you live in an area with a short growing season.
Why Are My Sunflower Seeds Not Sprouting?
There are a couple of possible reasons that your sunflower seeds are not germinating, even when it has been 4 to 11 days or more since you planted them in ideal conditions.
Your Sunflower Seeds Are Too Old
One common reason for a lack of germination is that the seeds you are using are too old. In that case, the germination rate may be low – or even zero.
Sunflower (helianthus) seeds tend to last about 2 to 3 years, and germination rates will naturally decrease with each passing year. For more information, check out this article from Clear Creek Seeds.
If you think old seeds is the issue, you can buy sunflower seeds from True Leaf Market here.
Your Soil Is Too Cold Or Dry
Another reason your sunflower seeds are not germinating has to do with soil conditions.
If the soil is too cold, then your sunflower seeds might not sprout right away (whether you are growing indoors or outdoors). They may sprout when conditions improve and the soil warms up.
Don’t wait too long to plant, because if soil temperatures get warmer than 78 degrees Fahrenheit (25.6 degrees Celsius), then your sunflower seeds will germinate slower (and at lower rates).
You can find information on frost dates on the Old Farmer’s Almanac website.
Finally, remember that if the soil is too dry, your seeds will not germinate. In some cases, they may even die before you have a chance to correct the problem.
Keep the soil moist, and consider using a humidity dome to help maintain the proper moisture levels in the soil and air.
If you have a problem with dry soil, check out this article for tips on how to address the issue.
How Big Should Sunflower Seedlings Be Before Transplanting Outdoors?
Generally, sunflower seeds should be planted directly in the soil outdoors. If this is not possible, then transplant them outdoors within 3 weeks of planting seeds.
The University of Minnesota Extension suggests transplanting sunflower seedlings after true leaves have formed. Remember that true leaves are the first leaves that grow on the plant after the cotyledons (the “starter leaves” or “seed leaves”).
For more information, check out this article on sunflowers from the Cornell University Extension.
Conclusion
Now you have a good idea of how long it takes sunflower seeds to germinate (sunflower germination time). You also know about the factors that affect time to germination, how to optimize for faster germination, and how to troubleshoot a lack of germination.
I hope you found this article helpful – if so, please share it with someone who can use the information.
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~Jonathon