How Many Seeds to Plant Per Hole, Pot, or Cell?
I recently got an email from Sally with a familiar question. It’s the same exact question that I had when I was a beginner gardener and wondered how to start seeds:
“I’m sure this is a silly question, but I always see it recommended to plant more than one seed per hole. But why? I just got a seed starting kit with some seeds and want to make sure I’m using them efficiently. Can you help me out?”
It’s a great question, Sally! Understanding the answer to this question will improve your understanding of gardening and seed starting in general, because the answer hinges on an important concept: seed germination.
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Answer One: Seed Germination Rates
Not all seeds are created equal. Some plant species have higher germination rates than others. Even within a single plant type, some of the seeds are older than others, causing the germination rate to go down.
Imagine you’re growing arugula and the average germination rate is 90%. If you plant a 72 plant starter tray with one arugula seed per insert, you can expect only 65 of those plant inserts to actually germinate (72 x 90%).
Now imagine you plant three arugula seeds per insert. Each of these seeds has a 10% chance of failing, so the probability of them all failing is 10% x 10% x 10% = 0.1%. This means that you are 99.9% likely to have the seeds in that cell germinate. So in a tray of 72 inserts, it would be extremely unlikely you would have any seeds not germinate — barring other factors that affect seed germination.
In short: Planting more seeds per hole increases chance you have perfect germination rates.
Answer Two: Seedling Selection
Just like not all seeds are created equal from a germination standpoint, not all seeds germinate equally. Sometimes you have a seed that shoots off like a rocket and becomes too leggy. If this was the only seed in your insert, you’d be forced to use it.
By planting 2-3 seeds per cell, you allow yourself to luxury of choosing the seedlings that look the strongest. All you have to do is determine which one you like the most, then snip off the other seedlings to kill them.
Exceptions to The Rule
Like most things in gardening, there are always exceptions to this rule of 2-3 seeds per hole.
If you’re planting large seeds like cucumbers, melons, or pumpkins, you should only use one seed per hole. However, you can still plant seeds close together and then thin them out once they’ve established themselves. You just want to avoid crowding these large seeds together so you don’t mess up the germination process.
If you’re growing certain herbs (cilantro, dill, basil), you can get away with planting multiple seeds per hole and leaving them all there as they germinate. These plants can handle being planted right next to each other and basically become one larger, bushier plant.
Now that you know how many seeds to plant per pot, you have a deeper understanding of seed germination in general. For more on seed starting, please check out the simple seed starting for hydroponics guide.
A common question I get by email is, "How many seeds should I plant in each hole or cell?". It's a good question with a great answer — read on to find out!
3 pitfalls of planting seeds too early!
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Like many gardeners, once the holiday clean up is done, my mind turns to garden planning and seed starting; especially with all the new seed catalogues arriving in my mailbox each day! However, January is far too early to start most seeds and sowing seeds too early is just as bad – maybe worse! – than starting them too late. Don’t waste your time, money, and supplies with early seed starting. Here are three pitfalls of planting seeds too early.
3 pitfalls of planting seeds too early:
1) Too little light – Those who rely on a sunny windowsill to start their seeds would be wise to wait until a little longer for seed sowing. Most plants need at least 10 hours of light in order to grow well, and in January, much of the Northern Hemisphere receives less than that. In my Nova Scotia garden, I only get about nine hours of light in early to mid-January. Too little light results in leggy, spindly seedlings, which will never make good garden plants.
2) An indoor jungle – For grow-light gardeners, lack of light isn’t a problem; as long as the light bulbs are hanging only about 3 inches above the plants. And, adequate light will eliminate the leggy factor and help produce sturdy, well branched seedlings. But, starting your seeds too soon can still be a problem. How? Seeds sown too early will result in bigger plants…. which then need to be potted up into bigger containers… which will quickly take over your seed starting area/house and cost you more money is potting soil, organic fertilizer and pots. Plus, you’ll need to be on top of watering, as those sizeable seedlings will need more frequent irrigation.
3) Big plants can bolt – And those big plants in the big pots? Well, they can think that they’ve reached maturity and start producing flowers and fruits while still inside your house. In the case of tomatoes, you may think this gives you an awesome head start to a homegrown harvest, but this is not the case. Tomato plants grow and yield best when they are transplanted before they begin to flower, 6 to 8 weeks from sowing seed. I start my tomatoes in mid-March, for mid-May transplanting. Bolting can also adversely affect other types of seedlings like broccoli, cabbage, cauliflower, squash, cucumbers, and pumpkins. This will reduce or eliminate your harvest, not hasten it.
So, if planting seeds too early is bad, when should you start your vegetable, herb and flower seeds? Refer to the seed packet, catalogue or company website. They should offer accurate advice on when to sow seeds for each type of plant. You can also find an excellent seed starting calculator here. Just enter your last average frost date and it will tell you when to seed indoors.
In the meantime, if you’re still itching to get seeding, try these simple indoor garden projects.
Savvy January sowing:
- Plant up a few pots or trays of shoots or microgreens. We love sunflower shoots, baby kale, and Asian greens. For best results, sow seed under grow-lights.
- Organize your seeds! I always have the best intentions to keep my seed boxes well organized. By September however, succession planting and repeated sowings has resulted in seed box chaos. Take this opportunity to go through your seed packets, discarding any that are old, and donating any that you won’t use again. You can also take inventory of what you have, which will help you decide what to order. Keep seeds organized in a photo box, photo album or other type of storage container.
- Now that you’ve organized your seeds, it’s time to go through your favourite seed catalogues and order fresh seeds. Be sure to check out some of the newly introduced varieties, like the 2017 All-America Selection winners!
Will you be starting any seeds indoors this spring?
Planting seeds too early is just as bad as planting them too late. Learn 3 of the biggest pitfalls of sowing seeds too early from Savvy Gardening.