Coaxing new life out of a seed is one of the highlights of the year for gardeners, right up there with harvesting perfectly ripe vegetables (at least in my opinion). I’ll never tire of watching delicate seedlings break through the soil and stretch towards the light (hopefully not having to stretch too far!) I also like the sense of accomplishment that starting seedlings inside offers me as winter drags on. It’s like bringing a tiny piece of spring’s vitality and optimism into my house.
Starting seeds indoors gives your vegetables, herbs, and flowers a head start so they can grow larger and have better (and longer) harvests or flowering periods. It’s simple and enjoyable to grow seedlings inside with a few basic materials and a little patience. Everyone knows that a little nurturing is healthy for the soul!
- Seedling tray with cells, drip tray, and cover
- Seed-starting soil mix
- Fluorescent or LED grow lights
- Heat Mat
- “Mister” spray bottle and watering can with rain nozzle
- Plant labels
- Face mask (optional) – we’re all quite used to them by now!
Don’t have time to go into great detail? Don’t worry, I’m not going to take it personally. You can jump straight to the section How to Start Seeds Indoors in 4 Easy Steps (and come back to the details another time. They’re really excellent details, I mean. Just a thought).
You can start seeds in almost any small container as long as it allows drainage but the easiest and most efficient choice is a seedling tray with cells (compartments). When it’s time to transplant, it’s easy to slide the plant and soil out of the cell and into the garden or a larger pot. These plastic trays may be reused for a long time. Please remember to thoroughly clean them before reusing them.
You’ll also need a drip tray to gather draining water and a transparent cover to keep moisture and heat in while your seeds develop.
Soil for Seeds
Seeds need sterile, lightweight, moisture-retaining soil that drains easily. E.B. Stone Organics Seed-Starter Mix is my recommendation. Put the dirt in a wide mixing bowl and hydrate it evenly with water before planting. This is when you might want to wear a face mask since the soil is very fine and dusty, and can irritate airways. After you’re finished, wipe clean any adjacent surfaces with a moist towel.
Light is critical! Unfortunately, our Pacific Northwest winters don’t provide enough light to allow a seedling grow large and robust (even in a south-facing window). It’s because of all the clouds). Do you desire seedlings that are pallid, gangly, and weak? I didn’t believe so. Well… you’ll need lights.
T12 or T8 fluorescents may be used, although T5 high power fluorescent lights or LED grow lights are more efficient. The great thing about LED lights is that they maintain the same brightness until they burn out. With fluorescents, the strength can wane as they age, so it’s recommended to change them every 12 months, even if they haven’t completely burnt out. Get fancy with red/blue spectrums or, if you don’t want your home to look like a nightclub, stick to all-spectrum white, which will work just as well.
Adjust the lights to be around 2-3 inches above the seedlings and maintain them there as the plants develop. A chain on hooks makes it easy to adjust the height of the lights. If your light source is fixed, you may simply alter the tray height. When your seeds have germinated, turn on the lights (the exception is lettuce, which needs light to germinate). Plants need 12-16 hours of light every day. A timer makes it simple; no need to remember to switch the lights on and off.
Consider the following scenario: you’re chilly, it’s dark, and it’s wet. Do you want to get up and do something? I for one would not. Then add some heat to the mix, and… well, I still wouldn’t want to wake up, but your seeds will. Many seeds can only sprout in higher soil conditions, and a heat mat may assist speed up germination while preventing fungal growth. After your seeds have germinated, you may remove the heat mat.
Mister and Watering Can
When your plants are germinating and seedlings are little, a spray bottle/mister is ideal for keeping the soil wet but not waterlogged. Once they’ve grown a bit, you can begin to water with a watering can that has a rain nozzle so the water is gently dispersed and doesn’t flatten your seedlings or you can also water from the bottom if you use plastic cells. Just fill the solid tray underneath your pots with an inch or two of water, which will be absorbed by the soil and protect your seedlings from flooding.
I recommend filling a large watering can or bottle with tap water and letting it sit for a few hours to a day to warm to room temperature. Seedlings don’t like cold showers!
I admit I’ve been known to skip labeling my seedlings, imagining that I would definitely remember which cell contained which precious seed. That’s correct. The more seeds you plant, the more you’ll need to identify them so you know what’s growing where. The plants may look distinctive when they’re mature but many seedlings look a lot alike when they’re just getting started.
I fashioned flags out of toothpicks, sticker labels, and markers and covered them with transparent tape. Although they won’t survive long inside the tray while it’s covered, they function well once the lid is removed (if I try to not drench them when watering). I really enjoy the colorful Rapiclip plastic plant tags, which can be moved to the garden with the seedlings and reused year after year. Just write the plant’s name with permanent ink. For either type of label, I tape them to the outside of the cover until the seeds germinate and the cover comes off; then I stick them into the soil.
The finest part is still to come: the seeds! Lots of vegetable, herb, and flower seeds can be started indoors and transplanted into the garden or into outdoor pots when the time is right. These are a few alternatives, along with their recommended sowing dates.
It’s always a good idea to check your seed package for precise timing and to determine whether you should plant that specific seed inside or immediately into the garden. Vegetables such as lettuce, arugula, and spinach may be planted outdoors as early as March. Since beets, radishes, and carrots resist being transplanted, they are usually seeded straight outdoors rather than inside.
Sow in January : arugula, lettuce, onions, scallions
Sow in February kale, lettuce, onions, pansies, parsley, peas, peppers, snapdragons, spinach, tomatoes
Sow in March Bachelor’s buttons, broccoli, cauliflower, corn, cosmos, eggplant, marigolds, nasturtiums, pansies, parsley, peppers, tomatillos, tomatoes, Swiss chard, zinnias, zinnias, zinnias, zinnias, zinnias, zinnias,
Sow in April basil, beans, bok choy, cucumbers, ground cherry, melons, pumpkins, winter squash, tomatillos, zinnias
How to Start Seeds Indoors in 4 Easy Steps
You’ve gathered your supplies, personalized it all to make it unique and beautiful, and you’re ready to start. Let’s get started!
Fill a large bowl with seed-starting mix and mix in a little water to evenly moisten the soil. Since this dirt is extremely fine and might irritate your airways, you should use a face mask.
Put the seed tray into the drip tray and fill each cell with soil to just below the top.
Plant your seeds. If the seeds are tiny, like lettuce or arugula seeds, sprinkle just a few of them over the soil; if they’re larger, like pumpkin, or nasturtium seeds, you can push 2 seeds into the soil in each cell (one is a backup in case one doesn’t germinate). Pour a bit extra dirt on top to cover the seeds, then water the area until it is wet.
Planting the seed at the same depth as its thickness is a decent rule of thumb. For example, lettuce seeds need only a tiny sprinkling of soil to cover them but a nasturtium should be covered with about 1/4” of soil.
Cover the tray and place it under your lights on the heat mat. Don’t forget to identify your plants!
Most seeds can germinate in darkness or light (one exception is lettuce, which needs light) but once the seeds have sprouted, keep the lights on about 12-16 hours per day. As your seedlings develop, adjust the lights or the trays to maintain the lights 2″-3″ above them.
Check on your seedlings once or twice a day to check whether they need to be misted. You want the surface of your soil to stay lightly damp because if your seeds dry out they won’t germinate but if they stay too wet, they could rot. Remove the cover after at least half to two-thirds of the seeds have sprouted. Since moisture evaporates more rapidly now, you should be extremely diligent about keeping the seedlings damp (but not waterlogged).
After the plants have been growing for a while and are larger, you can switch from misting to watering using a watering can (with a rain nozzle so you don’t bowl them over with a flood of water) or you can water from underneath, filling your drip tray to cover about the bottom quarter of the cells. The soil will absorb water as it is required. Whichever technique you choose, be sure to check them at least once a day to ensure they aren’t drying out.
If multiple sprouts have appeared, thin them when the first real set of leaves appears. I understand how difficult it is. It’s upsetting. Nonetheless, it allows the surviving seedlings to develop and flourish. Snip off all but one sprout at the soil line to avoid disturbing your favorite seedling’s roots (we all have favorites; it’s okay).
After two sets of true leaves have emerged, you can start fertilizing with a water-soluble fertilizer or fish emulsion (beware: fish emulsion is a great fertilizer but it has a certain… what shall we call it? a foul-smelling bouquet (not for the faint-hearted). Fertilize every two weeks after diluting your fertilizer to 1/4 the quantity advised on the packaging.
Your children have all grown up. Or at least they’re teenagers and you want them out of the house until they adjust their attitudes. In any case, the time has come to harden them off (sounds like tough love but it’s for the best). You may then plant them!
Harden Off Your Seedlings
Remember that first nice sunny day in April of last year? You put on your shorts, tank top, and flip-flops and dashed out the door to worship the sun goddess? Then, after a day of ecstatic frolicking, you came home and realized that your tender PNW skin was burnt to a crisp? So you’re sunburned, ashamed, and wishing you’d used a little more restraint? Seedlings, too, have the sensation.
The strength of the indoor lights is significantly less than that of the sun. As a result, you must gradually prepare them for the vast outside. This is referred to as hardening off. That will take around one week, give or take. Day 1: place your seedlings outside in a protected area in the shade for an hour or so, then bring them back inside. Day 2: repeat, extending the time by an hour or two. Day 3: Repetition, maybe with some early light.
Repetition, repetition, repetition. Each time allowing your plants to stay outside longer (if the night temperatures are moderate, you can even leave them outside overnight) and get a little more sun each day. These will be ready for planting by the end of the week.
Hardy seedlings can begin the process of hardening off once they have 3-4 true leaves. Begin hardening off your fragile plants one week before you want to put them outdoors.
A Few Planting Tips
Cucumber and squash don’t like it when their roots are messed with, so try not to overwork them while transplanting them.
Tomatoes should be buried deep. Otherwise, the law may come after them (joking). If you bury up to about 2/3 of the stem, roots will grow from each leaf node, making them stronger.
Be sure to water your new seedlings well after planting and keep a regular watering schedule. Since seedlings have little roots, they dry up rapidly.
When to Plant Your Seedlings Outside
The distance from the last forecast frost, which might damage half-hardy and fragile plants, determines sowing and transplanting dates. Our final frost date in Seattle may be as early as mid-March, but since it fluctuates, we normally set it for April 15th to be extra cautious. While everyone has a different perspective on when to transplant, consult your seed packaging for detailed instructions.
Transplant 4 weeks before last frost : scallions, spinach
Transplant 2 weeks before last frost Arugula, broccoli, calendula, kale, lettuce, onions, parsley, and snapdragons are some of the ingredients.
Transplant on our right after last frost Bachelor’s buttons, cauliflower, maize, cosmos, marigolds, nasturtiums, and pansies are among examples.
Transplant 2 weeks after last frost beans, bok choy, ground cherries, melons, winter squash, tomatillos, tomatoes, zinnias
Transplant at least 4 weeks after last frost : basil, cucumbers, eggplant, peppers
What is the best way to germinate vegetable seeds?
Moisten the newly planted seeds with a mister or a small watering can. To speed germination, cover the pots with plastic wrap or a plastic dome that fits over the seed-starting tray. This keeps the seeds wet until they germinate. Remove the lid as soon as you see the first indications of green.
What seeds should not be started indoors?
6 Plants You Should NEVER Start Indoors
- Root vegetables. Root crops simply don’t transplant well. …
- Squashes. Squashes (squash, zucchini, pumpkins) and cucumbers grow extremely fast and large. …
- Corn. Corn typically doesn’t transplant well. …
- Beans. Beans grow quickly as well. …
- Peas. Peas are similar to beans. …
- Cucumbers. …
When should seeds be started indoors?
In general, you should start seeds indoors 6 to 8 weeks before your area’s normal last frost date.
Is it better to germinate seeds in soil or paper towel?
Many seedlings germinate more faster when wrapped in paper towels (versus seeds that are started in soil). The heat, moisture, and controlled conditions inside a plastic baggie help them germinate in only a few days (or less, depending on the seed).