Aww spring! We’re not quite there yet, but it’s just around the corner. Which means it’s time to start planning (and planting) our 2024 gardens! Even though it may still feel like winter where you are, now is actually the time to start growing plants by seed indoors so they’ll be ready to plant in the garden as seedlings in the spring. Planting seeds is a fun way to get a jump-start on spring and also to save some money on plants. This easy seed starting guide will walk you through the process step-by-step.
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Supplies You’ll Need:
- Seed starting soil mix
- Mixing bowl
- Tray with cover
- Tray inserts (I like 3″x3″ or a 36 cell insert)
- Trowel
- Baby trowels (optional, but so handy!)
- Gloves (optional)
- Seeds
- Markers
- Heat mat
- Grow light (I also own this one, but it’s currently out of stock)
- Liquid fertilizer
Seed Starting Process:
Step 1:
First things first, let’s figure out what to plant! Determine what you want to grow, and how many of each plant you’ll need for your garden. You won’t be starting all your seeds at the same time, so making a calendar is key to knowing what to plant on what week. I’ve laid out the entire process of making a planting calendar here. Over the years I’ve started planting in both smaller cells (the 36 cell insert) and larger 3″ x3″ containers, so I add two columns to track how many of each I need for a given plant. For example, if I’m planting two Brandywine tomatoes, I put “2” in the “large container” column on the Brandywine tomato row.
Step 2:
Gather supplies! Here are all of my planting supplies and my heat mat laid out as an example. The seed trays I’m using are 1020 trays and one tray has the 36 cell inserts (usually configured as 6, 6-cell inserts) and one has the 3″x3″ containers. I like using the 3″ containers for larger plants like tomatoes because then I don’t have to re-pot them to larger containers before planting them in the garden. Smaller plants like flowers and herbs are fine in the 36 cell trays until being transplanted. If you’re using the 72 cell trays, know that you’ll need to re-pot all of your plants to larger containers to keep growing before they’re ready to transplant into the garden. I don’t know about you, but that’s way too much work for me!
Step 3:
Fill your bowl (mine is a mixing bowl from the dollar store) with the seed starting mix. I’ve linked my favorite (Black Gold), but Coco Loco is another good one. If you have an organic garden, make sure the soil is OMRI certified. Gradually mix in water until it’s a nice spongy consistency. If it’s dry enough to blow away as dirt in the wind, add more water. Don’t make mud though! We just want it to be damp without any dry spots.
Step 4:
Fill the tray cells and/or containers with the soil. Only fill enough containers for the plants you are planting this week. I usually cut apart the 6-cell trays unless all 6 cells will have the same type of plant. I like to fill to the top, shake them a bit, and then add a bit more soil. You don’t want the soil too loose, but you don’t want it too compact either, otherwise it’s harder for the seeds to root and for the roots to get the oxygen they need. Do you sense a Goldilocks theme going on here? A regular trowel works great for filling the 3″ containers, but the little trowels are awesome for the smaller cells.
Step 5:
Plug in your heat mat and set the tray on top. Create labels for each container since they’ll be moving around to different trays during the process. I learned quickly that it’s hard to remember what’s what without labels! My 3″ containers came with nice white labels, but I also cut up plastic containers (like the ones mushrooms come in) and use those as markers too. I’ve found wood and bamboo markers tend to get moldy, so I stay away from those even though I like their sustainability better.
Step 6:
Plant your seeds! I like to plant 2-3 per cell/container. If more than one sprouts, you will need to separate the plants into separate containers, or cut off the less impressive sprout. I make holes for the seeds with a toothpick, and also use the toothpick to help pick up small seeds and put them into the holes.
Step 7:
Add some water to the bottom of the tray to help create a humid environment. I put the water in the grooves, but not high enough to touch the pots. Cover with the lid. After a few hours, the covered tray should be like a greenhouse–nice and steamy with tons of moisture inside. If not, carefully open the lid and add more water to the bottom. Also make sure that your heat mat is warm.
Step 8:
Once the seeds sprout, move them out of the covered tray and into an uncovered tray under a grow light. The light should be 1-2″ above the tallest seedling. The light should be on 16 hrs a day. I have my trays on a collapsible stand, but I’ve also set them up on the counter in the past (as seen in this picture). The lights I linked come with a stand if you’re using them on a counter or table. Bottom water the seedlings in the uncovered tray by pouring 1/4″ of water directly into the tray (not on the containers/cells) every 2-3 days. Dump out any water that remains after 20 minutes. Once all plants have their true leaves (the leaves after the first “seed” leaves), add 1-2 drops of liquid fertilizer to one quart of water before you pour it into the tray.
Step 9:
One week before you’re going to plant your seedlings outside, begin hardening them off. Put them outside in the shade for 1-2 hrs. Add 1-2 hrs per day in indirect light. Once they have worked up to being outside all day, then keep them outside overnight and plant in the garden the following day. If you live in a dry or warm climate, you may need to water them more than normal at this point. Keep an eye on them!
Step 10:
Plant your beautiful seedlings in your garden! All that hard work paid off and your little plant babies are ready for their next adventure. Congrats!
Q&A
Here are a list of questions you might have and my best answers. If I missed anything, let me know in the comments!
Q: I can’t find either soil you recommended. Can I use something else?
A: Sure! Look for a soil that specifically says it’s for seed starting. Your local nursery can make a recommendation. If you garden organically, make sure it’s OMRI listed and approved for organic gardening. I’ve found that some seed starting mixes have large wood chips in them which I’d stay away from. The chips make it hard to plant the seeds accurately and also tend to get moldy when in the covered tray.
Q: Where do I get the trays, covers, and inserts? Can I use other containers?
A: I usually get the trays and covers at my local nursery. They usually have plastic inserts as well. For the past few years, I’ve been unable to find the 3″ cells locally, so this year I ordered the ones linked which seem sturdy and should be reusable. Big box stores like Home Depot, Lowes, and Walmart will also have the trays. “1020” trays are the standard size and fit perfectly under the grow lights I linked. I also know many people that will recycle empty food containers and use them for seed starting. This isn’t as efficient space-wise, but is a great way to be more eco-friendly. Do what fits with your lifestyle and budget.
Q: Oh wow–to grow all the things I want to grow would be a lot of different seeds. I thought I was supposed to be saving money here??
A: If you’re just starting out, it can definitely seem that way! However, there are sooo many sources of free seeds. My local library has a seed library where card holders can get 30 packs of seeds per year!!! Most cities also have seed exchanges, so look for those on places like Facebook. If you have friends or family members who garden, you can also ask them for a few seeds. Most will have plenty to spare.
Q: I’m going on vacation in February/March/April. What do I do?
A: Oh dear. This happened to me last year. Find a very kind friend or family member to babysit your seedlings. Make sure the lights are on a timer, and have them check on them at least every other day.
Q: Grow lights are really expensive! Do I actually need one? Can I just stick the tray in a window?
A: Sorry to say it, but in my experience grow lights are definitely a necessity. The seedlings grow much more bushy and healthy with the lights. The ones I’ve linked are the ones I’ve personally used, but certainly shop around for other 45W broad-spectrum LED lights. You may also want to use an LED garage light which would fit multiple trays underneath.
Q: Where should I set up my trays?
A: Aim for a warmish place without any cold drafts. My sprouts love it in the kitchen, which is the warmest room of the house in the winter. I have them on a collapsible stand in the corner. Last year I tried keeping them in the living room, but cold air from the front door completely stunted their growth. Also put them somewhere you’ll see them frequently. Seedlings should not be stressed for water and you’ll need to be monitoring them daily or at least every other day. Plus it’s so fun to check on them and see them growing before your eyes!
Now it’s over to you! Are you starting any plants from seed this year? I hope this easy seed starting guide was helpful and enables you to grow your own seedlings!
