How Many Seeds Do You Need To Grow A Plant?

When you’re planning for the upcoming season, you might want to start seeds indoors. Maybe you have trays and starter pots and you’re planning to plant multiple seeds. But you might wonder to yourself, how many seeds do you actually need to grow a plant?

It’s not as easy an answer as one seed to plant as some people think. In a perfect world that may technically be the case, but it doesn’t quite work that way. In reality, the answer is multifaceted. There are so many different considerations, from what you’re growing to how you sow it.

Before you get started, let’s cover a few of the things that will determine the number of seeds you need to grow one plant. We’ll also cover a few techniques that will put your seed-starting game on point. 

Understanding Germination Rates

The first consideration is germination rate. You can check your seed packet for this information. Germination rate refers to the percentage of seeds that will sprout into plants out of 100. So, if you have a germination rate of 90%, 90 out of 100 seeds will likely sprout if all basic conditions are met. 

It’s also essential to have fresh seeds. As seeds get older, their germination rate will decline. This is why most seed companies include the date that the seeds were packaged. Older seeds may still germinate, so you shouldn’t get rid of them entirely. But as a general rule, the fresher they are, the more viable they will be.

To achieve the highest germination rate, there are a few basic conditions that need to be met, particularly when sowing indoors. You’ll need a grow light, good seed-starting soil, and a heating mat for optimal results. On the other hand, you could even start in a greenhouse. 

If you have optimal conditions to help your seeds sprout, refer to the germination rate to determine how to plant. Sometimes the germination rate is present on seed packets. Sometimes you’ll have to do some digging.

Instead of thinking in terms of starter pot count, consider how many holes you’ll make in the soil. Tally that up, and compare that to the germination rate. Chances are you should plant at least two seeds per hole. 

Germination Rate Formula

When you find the germination rate, follow this formula to determine how many seeds should go in the same hole. Then begin planting seeds. Note this formula only works out perfectly in a controlled environment. 

It’s likely the rate of sprouts you witness won’t be exactly in line with the rate. The rate gives you a baseline for how many seeds per hole to plant. 

Number of Holes x Germination Rate = Number of Plants

Let’s start with 72 holes and one seed each that has a 70% germination rate. You would multiply 72 by 80%, and get roughly 57 sprouts. In this case, you can plant 2 to 3 seeds per hole and you’ll probably experience maximum success. 

Seed Size and Germination

Cucumbers, pumpkins, melons, and squash have high success rates. That’s because larger seeds generally have higher germination rates due to higher fitness. It may not be worth planting two to three seeds per hole here. However, if you’ve already sprouted two seeds in the same hole, just thin them. 

Plants with tiny seeds, like lettuce, tend to germinate at lower rates. You’ll have more success with these seeds when several are planted in one hole. Plant twice the amount of lettuce seeds compared to the ones mentioned above. 

How Many Seeds To Plant?

Seed size is not the only factor that determines germination rates. The condition of the planting area and the type of plant is also important. And you’ll want to make room for failure or loss in the hardening-off process.

Many times a single seed won’t be enough to produce a healthy plant. 

Fruits, Veggies, and Grains

Let’s look at some specific examples to explain the process of deciding how many seeds to plant.

Tomatoes have medium-sized seeds with a super high germination rate (about 98% on average). In this case, you can plant 1 to 2 seeds per hole and thin plants as needed after they sprout.

Giant onion seeds are medium-sized and have a hard casing. The seeds of giant onions also have a high success rate, especially when they are fresh. In this case, the 2 seed per hole rule applies.

There’s a reason people don’t often sprout berry seeds: they often have success rates of 50% and below. A single seed or just a couple of seeds will not become small plants easily. For berry plants, plant multiple seeds per hole. You’ll have a lot less success here than you would with larger seeds. 

Collard greens also have a pretty high success rate and can sprout easily with 2 or even 1 seed per hole. More than one seed gives you more success, and more to work with after hardening off.

Regardless of the germination rate, you should only plant 3 rice seeds or less per hole. This is because large seeds like rice can experience stress in the transplant process if there are too many sprouts in one hole. So don’t plant a whole bunch of rice at once.  

Flowers

One flower I’ve found sprouts very easily is calendula. These seeds look a lot like mealworms, with their twisted casings. They germinate at about 78%. The same goes for borage seeds. Both seed types are about the same medium to large size. 

Chamomile is one of those flowers whose tiny seed relies on numerous factors to successfully sprout. A lot of people I know (myself included) have trouble with chamomile because although the germination rate of the seeds is high on the packet, other issues like moisture or too fertile a soil type can make gardening with them difficult. That’s why you may have to use a large number of seeds to grow one plant of chamomile. 

Some smaller plants like lupine and alyssum self-sow in the garden and don’t need your assistance. In the case of self-seeder plants, just let them do their thing, and avoid the waste of starting them with soil you’ve mixed yourself. 

Herbs

When you plant herbs from seed, you’ll have to remain patient. Gardening with mint, tansy, dill, and parsley is super rewarding but you need several seeds of each type planted per hole. 

For instance, I grew a white sage plant from seed but had to use almost all the seeds I had before I could get it to sprout. The germination success rate for that plant was about 40%. If I had neglected to plant more than one seed my chances of having any luck at all would have been slim. Most herbs have a higher rate than that, but generally lower than that of watermelon, for instance. 

How to Thin Seedlings

If you’ve planted two seeds in a hole and both sprout, what now? Well, select the healthiest of the two and remove the other. Use small scissors to clip the sprout planted in the starter pot instead of pulling it out and disturbing the roots of the plant you’ve selected.

It may seem like a waste, but the roots of the eliminated plant will break down and provide nutrients to the other. 

Frequently Asked Questions