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In the dark, short days of winter, it is easy to daydream about the sunny days of spring and summer when your yard or garden are filled with blooming flowers and fresh produce ripe for the picking. Through food preservation practices of canning or freezing, you can get the taste of the fresh produce, but there really is nothing like going and picking a fresh tomato or frying up fresh squash right out of the garden. Thankfully, we can bring some of the joy of getting garden plants ready indoors even if the snow is still falling outside in early spring.
All plants start somewhere. Some plants do fine if you sow seed directly into your garden, while others germinate better in a controlled environment. This is where human intervention can come into play, and spring can start a few weeks early – in your own home.
One of the first steps to take when starting seeds will be to select your seeds. Select varieties that will meet the needs of your gardening goals. It also is important to consider the number of growing days for your area. Some varieties can be started outside, while others should be started inside so that you can have a bountiful harvest before the first frost in the fall. Furthermore, you can sow seeds mid-summer to have transplants for fall crops, like Brussels sprouts, broccoli or cabbage. Also, think about the source of your seeds. Be sure to purchase seeds from reputable suppliers. If you already have seed from the last season, it can be used if it was stored correctly. If you choose to store leftover seeds, keep them in an airtight container in a cool, dry space, or they can be frozen.
There are several options available when selecting a container to sow your seeds in. If you have a more restrictive budget or plan to start a few plants, consider using old butter or yogurt containers. Thoroughly wash the containers and punch holes in the bottom for drainage.
However, if you plan on having several different varieties or want to start several seeds, consider using solid trays or plug trays. There are benefits to both. Solid trays, also called flats, are sturdy and allow you to sow as many seeds as you please. Plug trays have individual planting cells, are useful if you want to start 10 to 20 seeds of each vegetable or variety, and allow you to save space. They also are easy to transplant out of. The biggest disadvantage of plug trays is that each plant will have a more limited amount of growing medium to grow in, which also will restrict water as the plant grows.
You may want to consider using peat pots or other biodegradable pots that can make transplanting simple since you will not need to remove the transplant from the container. However, these pots tend to lose water more rapidly.
When choosing a container, consider the size of the plant. If the plant will be large and grows fast or can suffer if the roots are disturbed, you may want to use a larger container, such as a cell pack or yogurt cup.
When it comes to growing medium, it is important that you use a germination mix or a soilless potting mix rather than soil from your garden. This helps keep the tender seedlings healthy and free of diseases that can come from garden soil. You have several options for potting mix and can even mix your own. It is important to note that you should not plant seeds in a waterlogged mix or too dry of a mix. If you can wring a steady stream of water out of the mix, it’s too wet and you’ll need to add more dry mix.
Many times, we consider the moisture level of our potting mix, but sometimes forget to consider soil temperature. When you purchase your seeds, the seed packet will indicate the optimal soil temperature range for germination. A soil thermometer can provide more information on the temperature of your soil and help you avoid the guessing game. Some seedlings will do fine with cooler soil, while others, like peppers, may need bottom heat to germinate. You can easily provide bottom heat by placing them on top of the refrigerator or using a heat mat.
Now that you have your seeds, container and planting medium, it’s time to sow! But wait, you might not have considered timing. Some seeds can take a while to germinate, while others can germinate in just a few days. This is when you’ll need to consider your growing conditions and what you’re seeding. Many seed companies have calculators or guides to help you decide when to start seeds. Generally, most seed packs will say when to seed indoors, so check the back of the seed packet to find out when to seed prior to transplanting outside. Some other factors to consider when determining when to start seeds:
When the time to plant arrives, fill the containers with the grow medium of your choice, be sure that it is moist and then, it is ready for planting A general rule of thumb when sowing seeds is to cover them with growing medium at a depth equal to two to three times their width. However, it is better to seed too shallow than too deep to ensure better germination of the seeds. To avoid the guessing game when you are planting or harvesting, it is best that you label your seeds from the beginning. Popsicle sticks, plastic spoons or tongue depressors are all good options for labeling. You can include the date you seeded, the type of seed, variety and any other pertinent information.
Once your seeds germinate, one of the most important keys to their success will be the amount of light that they receive before being transplanted into your garden. If you have a safe outdoor area, such as a hobby greenhouse, then you won’t have to worry. However, if you are seeding your plants inside your home, then lighting might be a challenge. Ideally, you’ll want to place your seedlings under an eastern- or south-facing window and rotate them to keep them from stretching toward the light, resulting in leggy plants.
If you do not have an ideal place in your home under a window, you may want to think about using grow lights. These lights offer an artificial form of light that acts as sunlight to provide the lighting needs for plants to photosynthesize. When using grow lights, keep them just above the plants and gradually raise the lights as the plant grows. This will help prevent etiolation (leggy plants) and will result in stocky, healthy plants ready for the garden.
Before your seeds germinate, you shouldn’t need to water. You can increase the humidity in your container by using a clear commercial cover, bag or film. Be sure it is airtight to prevent the media from drying out before and during germination. Once the seedlings germinate, bottom-watering will help keep the soil moist without potentially damaging the tender seedling. Use a solid tray to hold the water, then place the germination container in the water.
The bigger the seedlings get, the more water they are going to require. If your seedlings are inside your home or a greenhouse, they are going to need watered once a day so that they don’t dry out. If possible, maintain a moisture level like that of the media you initially placed in your containers.
Of course, too much of a good thing can be bad. If the soil is too wet or the plants are overwatered, damping off can occur. Damping off is caused by a fungus that thrives in cool, wet soil or potting medium. It can result in a loss of a whole tray of plants and causes infected seedlings to have thin, wiry stems that usually do not survive.
Some plants can stay in the container they are germinated in until they’re ready to transplant into the garden. However, if you are using small plug trays to germinate your seedlings, you’ll need to repot them. These can be “potted up” into cell packs or larger pots. If they are fast growing and it’s time to plant outside, they can go directly in the garden. It can be exciting to see plants emerge from the soil and you may question if they have enough room, but it is best if you wait to transplant until they have developed true leaves.
When you transplant your seedlings, handle them with the leaves. If you planted the seedlings in a plug tray, gently grasp the seedling at the base of the stem and gently pull from the tray, then move to the larger container that has been filled with moist potting medium.
Starting seeds indoors can be a rewarding experience as you watch the change from seed to seedling to a thriving plant, producing tasty produce or beautiful blooms.
References
Jett, L. (n.d.). Planting Schedules for Open-Field, Low Tunnel and High Tunnel Vegetable Crops in West Virginia.
Jett, L. (n.d.). Growing Vegetable Transplants for Field and High Tunnel Production.
Seed-Starting Date Calculator. (n.d.). Retrieved January 13, 2021, from https://www.johnnyseeds.com/growers-library/seed-planting-schedule-calculator.html
Authors:; and Michael Shamblin , WVU Extension Agent -
Last Reviewed: April 2021
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: germination rates.
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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 microgreens and the average germination rate is 90%. If you plant seeds in 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 multiple seeds at 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: Plant multiple seeds per hole to increase the chances you have perfect germination rates.
Just as 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 as your other plants grow.
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 germination in general. For more on seed starting, please check out the simple seed starting for hydroponics guide.
There are some general rules we can glean from all of the above information. The size of the seed will help you determine how to plant. If we were to average the number of seeds based on all seed sizes, you would plant 2 to 3 overall.
Let’s break it down by seed size, to give you a good sense of the kinds of formulas you can use to start seeds. If you’re planting multiple seeds at different sizes, you can simply use this rule to get going.
If you want to get even more exact, you can bust out your calculator to determine exactly how many seeds to plant based on germination rate. Use a ratio to determine how many to plant.
For instance, if you have a seed packet that has an 80% germination rate, and you want to grow 20 plants, you should plant at least 24 seeds, as the remaining 4 will make up the 20% lack of germination expected.
However, since you’ll want to plant in 20 starter cells, you should probably plant two seeds per hole and thin them to the most healthy plants once they’re large enough.
Q: How many seeds should I plant in each spot?
A: While it really depends on the seed type and its germination rate, on average you’re looking at 2 to 3 seeds.
Q: Can you plant too many seeds in one spot?
A: You can! However, you can always thin your multiple seeds that sprout seedlings after they sprout if needed. This will free up space for the ones you leave.
Q: Do you plant all the seeds in a packet?
A: If you’re planting over a large space, you may end up using whole seed packets. However, if you only need one or two plants, you may find you only use a few.
Q: How do I calculate how many seeds I need?
A: Multiply your germination rate to the number of plants you need, and then add a few more to up your percentage. You could also use the space you have to determine how many seeds to use.
Q: Why do you plant 3 seeds?
A: This helps 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.
Q: What seeds can I just scatter?
A: Most wildflowers do best when broadcast. The same goes for grains. Sometimes you can broadcast beets and carrots to maximize your harvest.
Q: What seeds should not be planted next to each other?
A: Any bad companions shouldn’t be planted together. A few of the most notable are corn and tomatoes, beans and onions, cucumber and rosemary, fennel and solanaceous plants.
Q: Does seed spacing matter?
A: It does! You don’t want to overseed if you have a limited amount of seed. Also you don’t always want to have to sacrifice seedlings to make room for others.
Are you interested in learning more about Rectangle seed starting trays? Contact us today to secure an expert consultation!