Too many plants or not enough – both are a problem when starting seeds. It raises the question: how to plan ahead so you get enough seedlings for transplant without wasting too many seeds.

So, how many seeds should you plant? **1st method: sow 2-3 seeds for each plant you want. After germination, thin seedlings to the strongest in each group. 2 ^{nd} method: take the number of plants you need and divide by the germination rate. Round up and add a few seeds (or 10%) to give a margin of safety in case of low germination rate.**

It all depends on the seed germination rate – this will have a big effect on how many seeds you need to plant. Planting old seeds, using non-sterile soil, or letting seeds stay too wet (or dry) will all lower germination rate.

In this article, we’ll talk about two helpful methods you can use to figure out how many seeds to plant. We’ll also go through some examples, complete with calculations so you can understand the methods. I’ll also have a link to a Google Sheets calculator for each method, so you can save some time on the math.

Let’s get started.

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## How Many Seeds To Plant (2 Methods To Calculate How Many Seeds You Need)

There are two basic methods you can use to figure out how many seeds to plant:

**1. Multisow and thin**(use this method if you want to guarantee a high germination rate “per cell”, “per pot”, or “per hole” – good if you have limited space for seed starting.**2. Calculate using germination rate**(use this method if you want to avoid wasting a lot of seed and/or you have plenty of space for seed starting.)

I think both methods are reasonable – it just depends on what your goals are. Let’s talk about how to use each method in practice.

Don’t worry about the math – I have a link to a calculator for both methods!

(You can learn how to test seed germination rates here).

### Method 1: Multisow & Thin

This method is pretty simple. The first part is to multisow. *Multisow* just means planting more than 1 seed in a given cell or pot (it could be 2, or 3, or more, depending on the germination rate and how much of a guarantee of germination you want).

For Part 1 (Multisow): first, you figure out how many plants you want. Then, multiply by 2 or 3. That’s how many seeds you will need to plant.

(If you are starting seeds in a tray with cells, you would plant 2 or 3 seeds per cell).

For Part 2 (Thin): after the seeds germinate, you “thin the seedlings”. This means leaving only the strongest, most vigorous plant in each cell or pot (the others would be cut off, or thinned). It seems cruel, but it decreases competition and ensures that the remaining seedlings will grow strong.

(You can learn more about when and how to thin seedlings here).

Let’s look at some examples of the multisow and thin method.

(You can find a Google Sheet with the calculator for Method 1, Multisow & Thin, here).

#### Example 1: Multisow & Thin

Let’s say you have a packet of tomato seeds with a 90% germination rate, and that you want 10 plants.

To ensure a high germination rate, you would sow multiple seeds per cell or pot:

**2 seeds per cell means a 99% chance at least one seed will sprout****3 seeds per cell means a 99.9% chance at least one seed will sprout**

With 2 seeds per cell, there is actually around a 10% chance that one or more cells (pots) will get no germination.

If we go with 3 seeds per cell, there is only around a 1% chance that one or more cells (pots) will get no germination. This is a pretty low risk, so 3 seeds per cell is probably fine.

Since you want 10 plants, we multiply by 3 seeds per cell to get 10*3 = 30 seeds. We need 30 seeds total, and we need to plant 3 per cell.

Later, if multiple seeds sprout in each cell (which is likely), then we thin the seedlings so that only the strongest one in each cell lives.

#### Example 2: Multisow & Thin

Let’s say you have a packet of pepper seeds with an 80% germination rate, and that you want 20 plants.

To ensure a high germination rate, you would sow multiple seeds per cell or pot:

**2 seeds per cell means a 96% chance at least one seed will sprout****3 seeds per cell means a 99.2% chance at least one seed will sprout****4 seeds per cell means a 99.84% chance at least one seed will sprout**

With 2 seeds per cell, there is actually around a 56% chance that one or more cells (pots) will get no germination.

If we go with 3 seeds per cell, there is still around a 15% chance that one or more cells (pots) will get no germination.

If we go with 4 seeds per cell, there is only around a 3% chance that one or more cells (pots) will get no germination. This is a pretty low risk, so we’ll go with 4 seeds per cell

Since you want 20 plants, we multiply by 4 seeds per cell to get 20*4 = 80 seeds. We need 80 seeds total, and we need to plant 4 per cell.

Later, if multiple seeds sprout in each cell (which is likely), then we thin the seedlings so that only the strongest one in each cell lives.

### How Many Seeds To Plant Per Cell

As you can see, the multisow and thin method is pretty good at guaranteeing good overall germination rates on a “per cell” basis. However, it seems like an awful waste of seeds:

**In the first example, we planted 30 seeds to get 10 plants (67% wasted!)****In the second example, we planted 80 seeds to get 20 plants (75% wasted!)**

If you want to save seeds, you can take a little bit more risk and plant fewer seeds per cell. If it works out that you get at least one sprouted seed per cell – great!

If not, then you can always try to transplant a seedling from one cell to another. Just know that transplanting a young seedling may not go so well.

Another option is to sow some more seeds to make up for the losses. This might not work so well for crops that take a long time to grow in an area with a short growing season.

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### Why Plant Two Seeds Together In One Pot?

As mentioned earlier, it makes sense to plant two seeds together in one pot to increase the “per pot” germination rate. This helps you to avoid an “empty pot” with no sprouted seeds.

The following table shows what can happen when you plant two seeds in a cell or pot instead of 1, along with probabilities of each (assuming the seeds are from a packet with a 90% germination rate).

Seed 2: Sprouts | Seed 2: Does Not Sprout | |
---|---|---|

Seed 1:Sprouts | 2 seedlings 81% chance | 1 seedling 9% chance |

Seed 1:Does Not Sprout | 1 seedling 9% chance | 0 seedlings 1% chance |

seeds from a packet with a 90% germination rate. There is an

81% chance of getting 2 seedlings, an 18% chance of getting

1 seedling, and a 1% chance of getting no seedlings

(so there is a 99% chance of at least one seedling).

### Why Plant Three Seeds Together In One Pot?

Planting three seeds together in one pot (instead of two) further increases the “per pot” germination rate. This helps you to avoid an “empty pot” with no sprouted seeds.

The following table shows what can happen when you plant three seeds in a pot instead of 1 or 2, along with probabilities of each (assuming 90% germination rate).

### Method 2: Calculate Using Germination Rate

For this method, you will need to know two things first:

**1. How many plants of that type you need (call it P)**– this is really up to you. It depends how much space you have available and the spacing between plants (check the seed packet or online).**2. The germination rate for that type of seed (call it R)**– this depends on the type of seed.

Now, we divide P/R and round up. This tells us how many seeds we expect to need.

Just in case we get unlucky (low germination rate), it helps to add a “margin of safety”. This could just mean sowing a few extra seeds, or it could mean adding a percentage (for example, 10% more). This margin of safety is up to you.

Generally, the germination rate is found on the seed packet or in the seed catalog (or on the website) you are ordering from. Germination rates can vary quite a bit, depending on the seed type and variety.

*Note that germination rates for seeds decrease over time. Some seeds (such as onions) can last only a year before germination rates decline rapidly. Others (such as radish) can last for several years before germination rates decline.

(You can learn about germination rates and how they decline over time here).

For this method, you can just plant one seed per cell, as long as you have enough space available.

Let’s look at some examples of the calculation method.

(You can find the calculator for Method 2, Calculate Based On Germination Rate, as a Google Sheet here).

#### Example 1: Calculate Seed Quantity Based On Germination Rate

Let’s say you have a packet of tomato seeds with a 90% germination rate, and that you want 10 plants.

Then R = 0.9 and P = 10. So P/R = 10/0.9 = 11.111… (round up to 12).

We will add a 10% margin of safety. 10% of 12 is 1.2 (round up to 2). So, we plant 12 + 2 = 14 seeds. This is much lower than the 30 seeds we planted using Method 1.

So, we would need 14 cells or pots to plant our 14 seeds. At a 90% germination rate, we would expect 14*0.9 = 12.6 seeds to sprout.

This gives us the desired 10 plants, with 2 or 3 to spare (you can thin those extra ones, or maybe find a place for them in larger pots outside of your garden).

Even if we have bad luck and the germination rate ends up being as low as 70%, we will still get 10 plants.

#### Example 2: Calculate Seed Quantity Based On Germination Rate

Let’s say you have a packet of pepper seeds with an 80% germination rate, and that you want 20 plants.

Then R = 0.8 and P = 20. So P/R = 20/0.8 = 25.

We will add a 20% margin of safety. 20% of 25 is 5. So, we plant 25 + 5 = 30 seeds. This is much lower than the 80 seeds we planted using Method 1.

So, we would need 30 cells or pots to plant our 30 seeds. At an 80% germination rate, we would expect 30*0.8 = 24 seeds to sprout.

This gives us the desired 20 plants, with 4 to spare (you can thin those extra ones, or maybe find a place for them in larger pots outside of your garden).

Even if we have bad luck and the germination rate ends up being as low as 67%, we will still get 20 plants.

The examples above show the reason that plants have lots of seeds. In nature, the germination rate is much lower than under ideal conditions we provide them with.

Even so, probability starts to work in the plant’s favor with large numbers of seeds.

Remember that in the worst case scenario, you can always buy some established seedlings (at least for tomato, pepper, and other plants).

## Conclusion

Now you know two methods to help you calculate how many seeds to plant. As long as you know how many plants you want and the germination rate, you should be able to use either method (the calculators should help too!)

I hope you found this article helpful. If so, please share it with someone who can use the information.

You can learn more about starting seeds indoors here.

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~Jonathon