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!
Name Origin: From the Greek word thyro, to sacrifice, due to its use as incense to perfume the temples. Read more on the History of Thyme.
Natural Order: Labiatæ
Growing Cycle: Short, Shrubby Perennial
Origins: Native to dry, stony places on the Mediterranean coasts.
Height: Usually under 12 inches.
Characteristics: Branched, slender, and woody stems that bear oblong, triangular, tapering leaves that are usually 1/4 to 1/2 inch long. The leaves are green on top and gray underneath.
Thyme Flowers: Little pink or lilac which form whorls and loose, leafy spikes.
Fun Fact: Thyme, particularly the low-growing species, are quite popular with gardeners making miniature and Fairy Gardens. There are many varieties to choose from and we’ve discussed them separately on our creeping thyme and Silver-Edged Lemon Thyme article.
How to Grow Thyme
Growth Cycle of Thyme
(thyme seeds, sowing, cultivation, propagation, harvesting thyme leaves, harvesting thyme seed and wintering.)
There are approximately 170,000 thyme seeds per ounce and 24 ounces will fill a quart container. Thyme seeds retain their germinating power for three years. Cuttings, layers and divisions all work well but the easiest way to grow thyme is from seed.
Growing Thyme From Seed
Because the seeds are so tiny, thyme seeds should be sown very shallowly or pressed into the soil with a fine layer sprinkled on top. Better to plant seed in a nursery bed where more attention can be paid to the tiny plants. This will also enable the more valuable garden space to be used for an earlier-maturing crop.
In the seedbed, plant thyme seeds in early spring with the drills 4 to 6 inches apart with 5 or 6 seeds per inch. If planting in volume, mix sand with the seed to prevent over-planting. Some farmers use as much as 4 parts sand to one part seed.
If you are considering growing thyme and adding it to your garden plan, you might want to check out our Thyme Companion Planting to ensure the best possible yields from all of your herbs, flowers and vegetables.
Thyme plants should be planted no closer than 8 inches apart. Ten inches is preferred but one plant per square foot is optimal.
Young, growing thyme plants should be set out in the garden or field in June or July, preferably in damp ground or just prior to a rain shower.
Thyme can be propagated by dividing the roots (should be done in April) and from seed. The finest plants are produced when grown from seed. However, Lemon Thyme smells sweeter when grown from cuttings or root divisions.
Harvest alternating plants in late August or early September. Harvest plants from alternating rows around three weeks later and the final crop of thyme should be harvested in October. If harvesting for drying, it’s best to harvest thyme just as they come into flower.
Harvesting Thyme Seeds.
Thyme matures unevenly from plant to plant.
While cutting the ripening tops is one way to obtain seeds, use of cloths, sheets, or paper bags may prove more productive. Around noon and again in late afternoon, gently shake the plants to encourage the ripe seeds to fall onto the sheets or into the bags. Collect the seeds and spread them in a warm, airy room to finish drying. Do keep in mind if the plants are wet or damp the tiny seeds may stick to the leaves and flower heads.
In colder climates, mulch your thyme plants with leaves or other garden litter to prevent undue thawing and freezing. In the spring, for best results; dig the plants, divide and plant in a new location.
(leaves and thyme oil)
Either fresh or dried, thyme leaves are used for flavoring soups, gravies, stews, sauces, sausages, dressings and many other dishes.
All parts of the thyme plant are fragrant because of the fairly high concentration of volatile oil. Like olive oil, there are grades of thyme oil with the first distillation being the most aromatic and desired. Both grades are used in perfumery and soap making. Some use the crystals that can form in thyme oil as a disinfectant.
Thyme is a popular aromatic and culinary herb that is a native of the Mediterranean. Growing thyme is fairly easy once you know the environment it prefers.