The ideal depth for sowing seeds has multiple answers because there are several factors that affect the success of seed germination.
Some of these factors may include the type of soil and where you are planting the seed.
Planting seeds at a depth 1.5 to 2 inches below the surface of the soil increases their chances of germination and development into healthier plants. At this depth, seeds have access to the ideal amount of warmth, moisture, and aeration. When covered, seeds are protected from washing away and being eaten by pests.
Planting depth can also vary with the seed variety, the location, and the type of soil in which the seeds are sown.
Further in this article, we have elaborated on how these factors affect seed germination and everything to look for in order to produce strong and healthy plants.
What is the Recommended Depth to Plant Seeds?
There are different answers to this question that we are going to answer.
There are drawbacks when seeds are planted both too deep and too shallow.
Some seeds need to be planted deeper, others shallow, and others have a moderate depth.
Despite having all these differences, there is a depth that is generally recommended.
The recommended depth to plant seeds is at least 1.5 to 2 inches within the soil.
This is the depth that seeds can get the necessities with ease and germinate as expected.
Additionally, in many cases, seeds need to be first dried before planting which also ensures successful germination.
See our helpful guide on drying seeds before planting.
What Happens if Seeds are Sown too Deep
When seeds are sown too deep within the soil, there is a high chance that the plant will grow weak, feeble, or even fail to germinate.
When you plant seeds too deep in the soil, they may not get enough warmth, moisture, light, and air which are essential for seed germination.
Some plant’s stems are not designed to push up firmly through long-distance above them.
This may not only make the stem grow weak but also make the plant die early.
When you plant seeds in clay soil, the seed may decay and fail to germinate at all because of how heavy the soil is above the seed.
The seed may also struggle to get adequate aeration and warmth which also prolongs the germination process.
What happens if Seeds are Planted too Shallow
As a farmer, you may be tempted to plant seeds too shallow so that they may emerge quicker.
Unfortunately, some plants may expose tender roots, which should not be exposed early at germination.
When you plant seeds too shallow, you might increase the chances of them being washed away, blown away by the winds, getting buried under the soil, and fail to germinate at all.
Some plants with different types of roots, like the corn roots, may not develop well, and may not grow uniformly.
This can lead to poor germination of the plant. The plant roots will be weak and will not support the plant adequately, resulting in poor yields.
In addition, planting seeds too shallow may expose them to predators like squirrels and birds.
Seeds that Can be Planted Shallow
Despite having some risks, there are seeds that require shallow planting to grow well.
When you plant seeds too shallow, the seed may not get a chance to open as it should, and these may not only lead to drying of the seed zone but also entertain pests to reach the germinating seed and destroy it easily.
These are the surface planting seeds. The majority of these seeds need extra sunlight to germinate.
Examples of surface planting seeds are:
- Celery seeds
- Poppy seeds
- Mexican marigold seeds
- Camaro seeds
These types of seeds should be surface planted for easy and sufficient access to sunlight.
What Depth to Plant Seeds
The depth of planting seeds may also vary according to where you want to plant them. Plants can be planted in plant pots, in the ground, and also in seedling trays.
Where you choose to plant your seeds may also affect the depth at which you should plant the seeds.
1. Plant Pots
Seeds, planted in pots should have drainage holes on the bottom. Plant pots should be at least 1 – 2 inches for sowing seeds.
Smaller seeds can be sprinkled on the soil’s surface in higher densities than larger seeds which require being buried individually below the soil’s surface.
Remember, the soil used to cover the seeds should be twice the size of the seeds.
If you are going to sow new seeds, there are many good soil options out there but I have found this potting soil made by Miracle-Gro from amazon to be most affordable and effective in keeping my plants healthy long after planting.
You can find it by clicking here.
2. In the Ground
Again, it all depends on the type of seed that you are planting in the ground.
The standard recommended depth of planting seeds in the ground is the same as we have recommended at the beginning of this article (1.5 to 2 inches).
3. Seedling Trays
These are trays that are made up of foldable plastic material. Sensitive and smaller seeds with a low germination rate should be sowed in the seedling trays.
This protects the seeds from harsh weather conditions that may destroy them.
When planting seeds in seedling trays, it is wise to plant seeds at least with a depth of twice their width.
The seeds should be sprinkled evenly over the surface of the compost with an interval of at least 2cm between each other.
When the seeds are germinated they can be watered using bottom watering which can promote healthier root development.
Can Soil Type Affect Plating Depth?
The type of soil can affect the planting depth of seeds. There are different types of soils into which you can plant your seeds.
We are going to see how these different types of soil can affect the planting depth.
We are going to focus on the four main types of soils that are;
- Sand soil
- Clay soil
- Loam soil
- Silt soil
Now, we are going to look into each of the above types of soil and know how each of them affects the seed planting depth.
Sandy soil is well known for bigger particles that allow water and air to pass through it at ease.
This type of soil may favor seeds that need the above necessities to germinate well.
Planting seeds on sandy soil may need one to plant the seeds at least twice deep as in any other heavier soil.
This is because sand soil gets washed away easily by water especially during rainy seasons.
Another reason why you need to plant your seeds deeper in sandy soil is that it warms up faster on the surface.
Sandy soil allows the roots of a plant to penetrate deeper into the soil where there is more water available than on the surface.
Seeds and plants planted on sandy soil should be planted deeper.
Clay soil is well known for being sticky and it does not allow fast drainage of water and oxygen because of its tiny particles which are about 0.002mm.
Clay soil is more compact hence makes roots grow through as expected. This kind of soil retains more water mostly on the surface than any other soil.
Seeds planted in clay soil should not go beyond 1 inch in depth.
Remember that you should not cover the seeds too deeply since there will not be enough water and oxygen that will be allowed to penetrate deeply.
Loam soil has a mixture of 20% clay, 40% silt, and 40% sand soils.
This is the best type of soil to plant seeds as it has a good ratio of particle size to air space and allows enough penetration of water and oxygen.
It also allows enough retention of water and nutrients; it has particles that will allow the roots to grow well and obtain the oxygen as needed.
Seeds should be planted at a depth of 2-3 cm in loam soil.
This is a type of soil that has fine particles; it has a high water retention rate which is enough and also, its fertility rate is high.
This is said to be the best type of soil to plant seeds due to its fertility rate.
Planting depth in this type of soil should be the standard one as we said ie 1.5 – 2 inches into the soil.
To sum up all the above, planting depth matters a lot as far as proper germination of a plant is concerned.
As we had learned earlier above, the recommended and standard depth of planting seeds is twice the diameter or the width of the seeds.
In addition, when you are planting seeds, it is important that you carefully read the instructions on how deep the seeds should be planted.
You should also be interested in knowing the best type of soil that you should use to plant your seeds.
This will help you know the depth at which you should plant certain seeds according to the type of soil that you would like to use.