If you are new to growing seedlings, you might want the entire Seed Starting 101 series:
- Seed Starting 101: Key Components To Healthy Seedlings
- Seed Starting 101: A Step-By-Step Visual Guide To Growing Seedlings At Home (this post)
- Seed Starting 101: Up-Potting
New to starting seeds? You might want to start by reading yesterday’s post, Seed Starting 101: Key Components For Healthy Seedlings.
Here’s how I start my seeds, step-by-step and in pictures. The eagle-eyed among you may notice that I show pictures of both 4″ pots and small multi-cell containers. The process is the same no matter what size pot you are using or, indeed, if you are not using any pots at all, but instead use repurposed yogurt containers, old cans or fancy soil blocks.
The seedling-holding vessel doesn’t matter, I just had to work with the pictures I had.
Assemble Your Gear
You will need clean seed starting pots. I like to hose my pots out and give them a quick dip in a bleach bath in late winter to prepare them for their upcoming season of use.
You will need adequately moistened planting mix. It is helpful to store your planting mix in a large plastic or rust-proof metal container.
You will also need seeds. Duh.
Loosely Fill your Pot with Planting Mix
I like to set my pot inside my large container of planting mix so when I inevitably slop planting mix everywhere, it just falls back into the container where it belongs. Fill the pot up, gently mounding it a bit. Do not pack or tamp down the soil, but do give your full pot a couple sharp taps on the counter (or ground or whatever) to settle the soil in place.
Fill Your Pots
Place 1-4 seeds in each pot (or cell). Try to get them towards the center but a little bit away from each other. This will make thinning easier later. I determine how many seeds to sow by thinking about the price of the seed, the germination rate and germination habits of the plant, and whether the plant is open pollinated (likely to have more plant-to-plant variation) or a hybrid (likely to have very little plant-to-plant variation).
Expensive seed, like $4.50 a packet imported hybrid cauliflower seed, should have near perfect uniformity and high germination and vigor. I would seed that very lightly, one or two seeds per pot, with an extra pot sown should one fail to grow. Open pollinated parsley, which is cheap, slow and not particularly reliable to germinate, I would sow more thickly.
Label Your Plantings
This is really important. Even when you’ve been growing your own seedlings long enough to tell a squash seedling from a lettuce seedling (ok, that’s pretty easy…) if you don’t label you’ll still look at a flat of brassicas and ask yourself, “now which one was the brussels sprouts and which one was the broccoli again?”I just write the name of the plant on some masking tape and stick the tape to the pot.
Cover Your Seeds With A Thin Layer of Soil
For big seeds, like squash and cucumber and artichoke, I push the seed into the soil with my pinkie finger up to the depth of my pinkie cuticle. If it’s a really big squash seed, like from one of the jumbo pumpkins or something, I might go a bit deeper. For the small seeds, like lettuce and brassica, I usually just sprinkle a fine layer of soil over the seeds.
Mist (Or Don’t) And Cover
If your soil was adequately moist to begin with, you shouldn’t need to actually water your seedlings, but you can lightly mist some water over the top to settle the seeds in. Just don’t get your potting mix too wet.
Then, cover your pots to create a high-humidity environment. I put plastic wrap over my seed trays, but propagation lids (little plastic seed tray covers) work well too. You can also stick your whole seed tray inside a large, clear plastic bag, like the kind that dry-cleaners wrap shirts in. As soon as you see a few seedlings poking up through the soil, remove the plastic.
Give your seedlings a week or so to get up and growing. If you are using good seed and have given your plants lots of lights they will grow well for you.
Thin Your Seedlings
This is absolutely critical. It took me years to get over my fear of taking scissors to my precious seedlings and voluntarily killing 50% or more of them. Try not to fall into the same trap.
With very few exceptions (like green onion and leek seedlings, which are grown crowded on purpose), you will get much better, stronger, more productive plants if you don’t make them compete for light and nutrition. So grab your small scissors and repeat after me: one pot, one plant – one pot, one plant.
Take a look at your seedlings. Select the stockiest, strongest looking one per pot, and cut the others off at soil level. More details on thinning here. I save all the brassica thinnings and eat them as super-trendy microgreens. That makes me feel somewhat better about the plant decapitation.
From here, just return your plants to their home under lights, move them outside to begin hardening them off or up-pot them as appropriate.