You might sprout seeds to start a garden, grow microgreens, or just for fun. In any case, you can make things go faster if you provide the proper environment for your seeds.
So, what do you need for seed germination? Seeds need water, oxygen, and warmth to germinate. Seeds are often germinated in soil, but you can also germinate seeds without soil. Most seeds do not need light, but all seedlings need light after germination.
Of course, giving seeds the proper water, oxygen, and warmth will improve germination rates and speed up the process.
In this article, we’ll talk about what seeds need for germination (and what is optional). We’ll also discuss ways to speed up seed germination.
What Do You Need For Seed Germination?
At a minimum, you need the following for seed germination to occur:
- Water – seeds need enough moisture to germinate. However, too much water can “drown” them by preventing the intake of oxygen.
- Oxygen – seeds need oxygen to “breathe” (respire), as do other organisms. They also produce carbon dioxide, which needs to move away from them (otherwise, they suffocate.)
- Warmth – seeds that are too cold or too hot will go into dormancy. Temperatures closer to the ideal range will speed up germination.
According to the Penn State University Extension, viable seeds are living things. As such, they need the conditions listed above in order to “wake up” and start using their stored energy to germinate and start growing into seedlings.
Soil and light are not required for most seeds to germinate, but there are some exceptions (more on this later!)
Right now, let’s talk about water and how it impacts seed germination.
Water For Seed Germination
All seeds need water for germination. However, providing seeds with enough water for germination is a delicate balance.
A lack of water will prevent germination from occurring. A dry spell after watering can damage or kill seeds.
On the other hand, too much water can drown seeds before they can germinate. Seeds need to be able to take in oxygen and get rid of carbon dioxide. Too much water prevents this from happening.
How Much Water Do Seeds Need To Germinate?
Seeds need consistent moisture to germinate. According to the Penn State University Extension, soil that is 50% to 75% saturated with water is ideal.
With too much water, the soil will be soggy for a long time after watering. You can always add water more often if it dries out, but it is difficult to remove water once too much has been added.
In areas with dry air, you might need to water a little bit every day to keep seeds moist enough for proper germination.
How To Keep Soil Moist For Seeds
There are two good methods you can use to keep soil moist for seeds:
- Spray bottle – this allows you to water more precisely, making it easier to avoid over watering. It also allows you to water only a portion of a seed tray if only one part of the tray has dried out.
- Humidity dome – this provides an environment (usually a plastic tray and cover with a vent) that retains moisture for seeds. You won’t need to water as often with a humidity dome in place.
As an added bonus, a humidity dome helps to retain warmth, which seeds also need to germinate. Of course, you can use a spray bottle for precision watering and a humidity dome to retain the moisture.
You don’t need to use a humidity dome for seed germination – they will still sprout without one. However, it can increase germination rates and save you time & effort.
You can make a humidity dome out of all sorts of different materials, including:
- Plastic containers and lids
- Plastic wrap
- Food trays
Just be sure to remove a humidity dome right after the first leaves appear on seedlings. Otherwise, your seedlings are more likely to suffer from mold problems.
How To Keep Seeds Moist (No Soil)
It is possible to start seeds without any soil at all. However, this still requires some type of growing medium for the seeds.
This medium will allow the seeds to stay moist. It will also give them a place to anchor their roots.
For example, you can use a setup as simple as a paper towel with a plastic bag to keep seeds moist without soil:
- First, wet the paper towel so that it is damp, but not soaking wet (wring it out if necessary!)
- Next, lay down the paper towel and put seeds on half of it (just one side.)
- Then, fold the other side of the paper towel over the seeds (this gives them more contact with a wet surface.)
- Finally, put the folded damp paper towel and seeds inside a plastic bag (seal the bag to retain moisture inside.)
As an added bonus, the bag will help the seeds to stay a little warmer. Just remember to keep an eye on the bag.
If it is sealed, you may want to open it once in a while to give the seeds some more oxygen. This will also help to keep the seeds from overheating if you leave them in a sunny spot.
Also, don’t let the paper towel dry out completely. Use a spray bottle to add more water to the bag if necessary.
Note: you can also use a sponge as a growing medium for seeds. You can learn more about growing seeds in a sponge in my article here.
Keep in mind that some seeds do not transplant well after germination (for example, carrots.) For those plants, it would be wise to sow your seeds directly into the soil in your garden.
Some seeds have a hard coating that prevents water and air from getting through (for example, morning glory). For those seeds, scarification can help to speed up germination.
Scarification means changing the seed coat so that water and air can get through. Scarification can be done with heat, chemicals, or by scratching.
You can use a hard or sharp object to make a small nick in the seed coating. Don’t be too rough – you don’t want to crush the seed or cut it in half!
Scarification is really just a way of speeding up a natural process. In nature, seed coatings eventually get broken down by the environment so the seed can germinate.
Scarification just helps the process along.
Oxygen For Seed Germination
Water alone is not enough for seed germination – seeds also need oxygen to sprout. According to the University of Illinois Extension, seeds absorb oxygen through their coating.
However, providing enough oxygen is somewhat at odds with providing enough water.
With too much water, seeds cannot get enough oxygen (or they cannot get rid of the carbon dioxide they produce via respiration).
Without enough water, seeds may have enough oxygen, but they will get damaged or die due to the dryness.
As mentioned earlier, scarification can help to break down a seed coating to let oxygen through.
How Much Oxygen Do Seeds Need To Germinate?
Seeds need oxygen before they sprout, since they need to use respiration to grow. Respiration basically means using oxygen and sugar to produce energy.
Seeds may not get enough oxygen if:
- The soil is too wet
- The soil is too compact
- They are buried too deep
To avoid suffocating seeds, water them carefully with a spray bottle. Over watering is a common cause of seed suffocation.
When planting seeds, pat down the soil, but don’t pack it down too hard. According to the Iowa State University Extension, this will allow oxygen to move through spaces between soil particles and make its way to the seed.
Finally, remember that it is possible to plant seeds too deep. A good rule is to bury seeds at a depth of 2 times their diameter, but there are exceptions.
Warmth For Seed Germination
Even with proper water and oxygen, seeds won’t germinate properly without the correct temperature. If they are too cold or too hot, seeds will fail to germinate.
The ideal temperature range for seed germination can vary quite a bit, depending on the plant species. However, a temperature of 75 degrees Fahrenheit (24 degrees Celsius) is a good target for most plants.
Proper temperatures are necessary for seed germination. The perfect temperature for a given seed will speed up the germination process.
For example, tomato seeds will germinate in just 6 days at temperatures of 77 to 86 degrees Fahrenheit (25 to 30 degrees Celsius). However, it can take tomato seeds 43 days to germinate at a temperature of 50 degrees Fahrenheit (10 degrees Celsius).
Mother Nature may not cooperate with your efforts to keep seeds warm for germination. Luckily, there are ways to keep seeds warm despite the cold.
How To Keep Seeds Warm To Germinate
There are lots of ways to keep seeds warm for germination, whether you are starting them indoors or outdoors.
For example, you can use:
- Seedling heat mat – this is used to warm a seed tray from below. They work well, but they need electricity to run.
- Humidity dome – this keeps soil moist and retains heat for seedlings. It doesn’t need power, but it doesn’t generate heat.
- Enclosed box – if insulated, a box will retain warmth for seedlings.
- Space heater – this can keep an entire room warm if you are starting multiple seed trays for germination.
- Cloche – this is often made of clear plastic to protect plants from cold, wind, and pests. It can trap heat in the air and soil beneath to keep seeds warm.
- Cold frame – this is like a greenhouse, but much shorter. It is used for growing shorter plants (lettuce, spinach) or for keeping seeds warm for germination.
- Greenhouse – this gives you the most space, and allows you to grow taller plants. It will also keep seeds warm while they germinate.
- Plastic – a layer of plastic over soil can trap heat from the sun underneath to warm up the soil for seeds.
Do Seeds Need Light To Germinate?
Most seeds do not need light to germinate. However, there are some exceptions.
For example, the following seeds need light to germinate:
Other seeds, such as onions and pansies, prefer only a shallow layer of soil to germinate.
Of course, all seedlings need light to grow after germination. Without light, there is no photosynthesis.
Without photosynthesis, plants cannot produce energy for growth.
Do Seeds Need Soil To Germinate?
Seeds do not need soil to germinate. Although we often start seeds in soil, it is not necessary for germination.
For example, you can use a soilless growing mix to germinate seeds. For example, this soilless seed starting mix from Gardener’s Supply Company contains:
- Canadian sphagnum peat moss (If you want to try this water-absorbing material, you can find a large bale of peat moss online from Ace Hardware).
- Wetting agent
- mycorrhizae (Glomus intraradices)
You can also opt for a soilless growing method such as:
- Hydroponics – hydroponics does not use soil. Instead, plants are grown in water, which is really a nutrient solution. Pots with a growing medium (such as rockwool) are used to anchor the roots.
- Aquaponics – this is like hydroponics with fish in the water. The fish produce waste, which helps to fertilize the plants. The plants clean out the water, which keeps it clean for the fish.
- Aeroponics – this method uses a nutrient mist to give plants just enough water and nutrients. This avoids wasting water, and this method uses much less water than conventional gardening or farming.
Now you know what seeds need for germination and how to provide it. You also know how to speed up the germination process and improve germination rates to avoid wasting seeds.
If you are looking for a foolproof, soil-free microgreens growing kit, try out The Good Box (you can learn more here!)
You might also find it helpful to read my article on what seeds to start indoors (to transplant out later in the season after the soil warms up!)
I hope you found this article helpful. If so, please share it with someone who can use the information.