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!
Growing Lavender From Seed
With its exquisitely sweet scent and colorful blue and purple blossoms, lavender has been prized by gardeners since ancient times. While most home gardeners today grow it more for its beauty and fragrance than for its perfume oils, lavender remains a popular fragrance for home and garden use. With patience and the right garden conditions, you can add lavender to your borders and flower beds inexpensively by growing it from seed.
Before investing the time and resources into growing lavender from seed, make sure that your garden in suitable for lavender cultivation. Lavender requires well-drained soil and bright, full sunshine in order to thrive. It’s a Mediterranean plant that likes hot, dry conditions. Give it too much pampering, and it sulks. If you have a spot in the garden that seems to bake under the hot summer sun, consider planting lavender there. A lavender hedge, used to edge a walkway or surrounding a rose garden, is a classic use of this timeless perennial. Lavender can also be grown in pots, window boxes and herb gardens.
Lavender Varieties from Seeds
Lavender isn’t the easiest plant to start from seed. Some varieties, in fact, cannot be grown from seed and require stem cuttings. If you’re new to starting seeds, you may want to start your lavender collection with potted plants purchased from your local garden center or from a reputable mail order source.
Lavender seeds can be purchased at home and garden centers or through mail order catalogs. The most common varieties started from seed include ‘Hidcote Blue’ and ‘Munstead’, both of which are varieties of English lavender (Lavandula angustifolia). Each of these classic varieties blooms abundantly and provides a strong, sweet fragrance.
Preparation for Seed Starting
It is easiest to start lavender from seed indoors 8 to 12 weeks before the last estimated frost date for your gardening zone. Give your seeds plenty of time to germinate and develop. Lavender is slow to start from seed. A simple plant light suspended over a table provides adequate illumination to germinate lavender seeds. A timer attached to your plant lights can be a lifesaver on busy days, ensuring that the seeds and eventual seedlings receive the necessary 12 to 14 hours of light each day.
Because lavender likes hot weather, a seed starting mat will help the seeds germinate more quickly. These special mats are waterproof and moisture resistant, and provide steady, even heat to seed trays. You can find them through online stores, catalogs and garden centers.
You can use seed starting trays or pots to grow lavender from seed. Make sure that the containers you use have adequate drainage holes, and sterilize any containers or trays you’re re-using from previous years before planting your lavender seeds. To sterilize containers, mix one cup of household laundry bleach in one gallon of water and soak the pots or trays for 10-15 minutes. Remove and rinse with clear, cool water until all traces of the bleach solution are gone. This kills any microorganisms lurking about from previous years. Be sure to use the bleach solution in a well-ventilated area.
The best potting mix for lavender is one that offers excellent drainage. Use sterile seed starting mix available from the garden center. You can mix more vermiculite into the seed starting mix to increase the drainage. Avoid mixes with added fertilizers or excess peat, which increases moisture.
Starting Lavender Seeds
Fill the clean seed trays or pots with soil mixture, and add one or two lavender seeds per pot or seed starting cell. Gently press them into the soil with your finger, but make sure they’re not completely covered; lavender seeds need light to germinate. Use a spray bottle to mist the seeds, and then place them on the heating mats and under lights. Mist the seeds every day so that they are slightly damp, but not wet. Set your light timer and make sure that the seeds and seedlings receive at least 12 hours of light per day.
It will take at least two weeks before lavender seeds germinate, and they do not look like mature lavender plants when they finally emerge. They tend to look like blades of grass when they finally do sprout, but eventually you’ll start to see them develop the traditional needle-like lavender leaves.
Be patient, as some varieties take a little longer than others to sprout. Once the seeds germinate, water lightly with a watering can when the soil becomes dry. Keep the seedlings warm and provide plenty of bright, full light until they grow several sets of leaves.
Hardening off the Seedlings
Before planting the seedlings in the garden, it’s important to acclimate them to the outdoors, a process called “hardening off.” Once all danger of frost is past, bring the seedlings outside during daylight hours. Keep them in partial sunlight for the first few days, and water well. Bring them indoors at night. Repeat this process, making sure the plants receive adequate light and moisture, for at least one week before planting the seedlings in the garden. This helps your seedlings adjust more easily to garden conditions after growing under controlled indoor conditions.
With its heady fragrance, beautiful color and ability to attract pollinators to the garden, lavender deserves pride of place in your flower beds, containers or borders. If you have full sunlight and are ready to try your hand at growing lavender form seed, with a little patience and luck you may have beautiful plants this summer.
With its exquisitely sweet scent and colorful blue and purple blossoms, lavender has been prized by gardeners since ancient times. While most home gardeners today grow it more for its beauty and fr…