Starting seeds indoors without grow lights is simple if you follow this step by step tutorial. This seed starting system works for several different vegetables, herbs, and flowers.
So many things to love about starting seeds indoors: It saves money, it’s fun, rewarding, simple, but also just enough challenging.
The best part about starting seeds indoors is you can scratch that gardening itch in the middle of winter, in the comfort of your own home.
Every year I start hundreds of seeds, indoors, in winter. I mostly grow vegetables, herbs, and perennial flowers.
I’ve started thousands of perennial flowers for my backyard nursery using this seed starting method as well as the winter sowing in Milk Jugs method.
It’s important to point out, this system is for starting seeds indoors. Not growing plants inside. This is an important distinction. Once a seedling becomes established it needs to be exposed to light with UV rays. Since this system doesn’t use expensive grow lights that are needed to grow plants inside, the idea is to just get the seedlings started and then move them outside where they can get the sunlight they need to grow strong.
Step 1- Buying Seeds
Take your time on this step. If growing vegetables and herbs, think carefully about quantities.
Experiment with growing a large variety of edibles rather than large quantities.
The last thing you want is a garden with a 100 zucchini ready for harvest while still buying other produce at the grocery store.
If growing perennials or other flowering plants, do plenty of research to make sure your plants will thrive in your growing zone.
Park Seed is one of my favorite places to purchase seeds online.
Step 2- Timing, When to Sow Your Seeds
Figuring out When to Start Your Seeds Indoors is one of the most important parts of this whole process. This is when you have to do some research:
For vegetables, herbs, and fruits check out this amazing planting schedule.
Chances are, a lot of the vegetables you plan on growing are listed. You can search based on your zone and the site will tell you approximately when to start your seeds.
For perennial flowers, or vegetables that aren’t listed, simply do a google search: ‘when to sow (seed variety)’.
Look for search results that tell you the number of weeks to sow indoors before the last frost.
For example, if you google ‘When to sow Cherry Tomatoes’, you will get a result that says ‘sow indoors 6 weeks before the last expected frost date.’
In this example you will count back six weeks from the date of your last expected frost date and this is when you will start sowing your cherry tomato seeds.
To find your last frost date simply type in your zip code after going to this link: frost date.
Step 3-Cold Stratification (If Necessary)
Once you’ve received your seeds, and figured out when your seeds need to be sown, check the seed packet, catalogue, or website you purchased your seeds from to see if the seeds need to go through a period of Cold Stratification. Cold Stratification is a period of cold temperatures in a moist environment that seeds need to go through to yield a higher germination success rate. Seeds should go immediately from cold stratification to being sown, so again you have to figure out your scheduling. In the previous step you figured out when you need to sow your seeds. Since most seeds require 4-5 weeks of cold stratification, count back an additional 4-5 weeks before the date you determined you need to sow your seeds. The refrigerator is the perfect environment for cold stratifying seeds. Follow these steps to cold stratify seeds in the refrigerator:
- Simply soak the seeds in water for 1 hour, then place the seeds on a paper towel. Don’t drain the water off, instead let the water transfer to the paper towel, making it a little damp.
- Wrap the seeds up in the paper towel.
- Place the wrapped paper towel in a plastic zip lock bag. I like to make a couple of small holes in the bag so it doesn’t get to moist and moldy.
- Place the zip lock bag in the refrigerator and leave them in there during the recommended cold stratification period.
Information on how long to cold stratify seeds should be on the packet, catalogue, or online. Usually a cold stratification period of 4-5 weeks is ideal.
Step 4- Materials
- Purchase bags of a soil-less potting mix. I would also recommend buying a little bit of seed starting mix.
- 6 pack cells which can be any size you want. I prefer 48 count cells.
- Plastic seed trays to hold the 6 packs. I like to double up on seed trays to add stability.
- Plastic domes that fit over your seed trays. These plastic domes will cover your seeds until germination.
I get most of my cell packs, seed trays, and plastic domes online at Growers Supply.
Your materials should look something like this:
I leave out the last two 6 pack cells for watering and rotating purposes.
Step 5- Fill With Potting Mix
At this point it is time to scoop the potting mix into the cells.
Fill all cells to the top and tamp down lightly. I like to stack 5 empty 6 packs together and use the bottoms to tamp down. This also gives me defined squares so I know where to place my seeds.
Next, top off the cells by sprinkling in your seed starting mix.
Do one more light tamp so you can see the squares.
Once you got your cells full of potting mix it’s time to grab your seed packets!
Step 6- Sow Seeds
For larger seeds plant 1 seed per cell.
For smaller seeds, sow 2-3 seeds per cell. For really small seeds it’s a good idea to just sprinkle some into each cell. No need to get crazy trying to count. Only a small portion of small seeds will germinate so don’t attempt to count each one.
As the seeds germinate you will eventually thin out each cell so that only one seedling is growing per cell.
Should You Cover the Seed with Potting Mix?
It depends on the size and also the seed variety. Some seeds require light for germination while others need the dark.
Generally, I push larger seeds a little into the potting mix so they are covered. For smaller seeds I usually leave them on top of the potting mix and just tamp down so there is good seed to soil contact.
Step 7- Labeling
At this point you’ve got your seeds sown. Now what?
Now would be a good time to make sure you have labeled each seed tray. It’s too easy to forget what you have planted, so make sure you label your trays!
Step 8- Water Trays
Fill each tray to the top with water. Wait 10 minutes as the potting mix soaks up the water. After the initial soak up add water if needed so that you’re leaving the tray filled with one inch of water.
After watering, cover each tray with a plastic dome. A lot of times the domes will come with the trays but if not make sure you get a size that is compatible with your seed tray when you are purchasing the trays.
Most of the hard work is done, it’s time to put them under the lights!
Step 9- Place Seeds Under Lights
Contrary to what most people think, you do not need grow lights to start seeds indoors.
Remember, we are only getting seeds started, not growing plants.
Seeds don’t need intense sunlight to get started. The best, and cheapest option is to get a shop light, or a bunch of shop lights depending on how many trays of seeds you have.
A shop light comes with hanging chains and you will most likely have to purchase the two fluorescent light bulbs. I like to use t-12 fluorescent bulbs.
It’s important to hang the lights using the chains because you want the lights to be as close to the seeds as possible. This way they get the strongest amount of light.
The chains allow you to keep the lights close to the seedlings and as they grow you simply adjust the chains.
Look at how close these lights are to the plastic domes…
There are many ways to setup the lights depending on how many seeds you are sowing.
I built the shelves above using strapping and a couple sheets of plywood. Don’t be afraid to experiment with different setups. Even store bought shelves and racks are fine for starting seeds indoors.
Step 10- Growing On
Ok, you’ve got your seeds sown, trays watered, plastic domes installed, and your seeds are placed under your shop lights.
Your only responsibility at this point is to make sure you leave those lights on for about 14 hours a day. I shut the lights off before going to bed.
Depending on what you are growing, you could see some germination within a week. Other seeds might take several weeks. Remember, you want to start your seeds that take the longest first.
Once all, or most of the seeds in a tray have germinated, remove the plastic dome. At this point you want to continue watering so the soil is moist but not soaking wet.
I recommend filling the trays with about half an inch of water. Once the tray is pretty much empty you can refill with another half inch of water. Don’t over water at this point because this is when your seedlings are susceptible to damping off disease, Or Fungus Gnats.
It’s also a good idea at this time to add in some Miracle Grow plant food while watering. Simply follow the instructions on the back to get the right dilution.
When you take the dome off your seedlings, run a fan for several hours. Personally I had a fan running at all times. This helps strengthen the seedlings and prevents disease.
As seedlings continue to grow, thin out the weaker ones so there is eventually one seedling per cell.
- Pro Tip 1– When thinning seedlings don’t pull them out. Doing so could damage the root system of the seedling you are trying to keep. Instead, cut them using pruning snips.
- Pro Tip 2- Add a fan to the seed starting area to create air circulation. This strengthens seedlings and helps prevent disease.
Be sure to raise the chains on your lights as needed so the seedlings don’t contact the lights. Just make sure you keep the lights as close as possible to your seedlings without touching them.
Warning! If the lights are too far from the seedlings it will cause them to stretch towards the light. They will become thin and lanky and will flop over. If this happens your seedlings are pretty much ruined.
What Should You Do Once Seedlings Are Established?
First off, congratulations for coming this far. At this point you should have a bunch of seedlings that are starting to look established. Your next step is to harden off your seedlings.
Knowing when to start hardening off your seedlings is important. And this is when the timing of everything becomes crucial!
The weeks following germination, you want to wait until your seedlings get some true leaves.
When a seedling germinates it has tiny Cotyledons. These are baby leaves that a seedling only gets while it is germinating. After that, it gets its true leaves.
If you did this whole process prematurely then the weather may still be too cold outside and you will be forced to keep your seedlings under lights. If left under lights for too long they will most likely become thin and leggy and start to flop over.
Remember, the lights you’re using are very weak compared to the sun and are not adequate to give the seedlings the energy they need. Your seedlings need to be introduced to sunlight!
At this point your seedlings need to be hardened off and moved outside. If you got your timing right the weather should be good enough to allow you to do this.
If you got your timing wrong your seedlings will need to spend more time under the lights and they could grow thin and floppy.
You are better off starting seeds indoors too late than too early!
Step 11- Hardening Off Seedlings
I’m not gonna lie, hardening off is a pain in the but in my opinion. This is the one part of starting seeds indoors that feels like a chore to me.
Your plants just spent several weeks in a fake environment. The temperature was constant, watering was constant, there was no wind, and the lighting wasn’t even close to the intensity of the sun.
If you were to just put your seedlings outside and leave them, they would certainly die. That is the quickest way to kill a lot of plants!
You have to gradually expose your plants to the outdoor elements. This takes time and patience!
If you don’t have a cold frame, the next best thing you can do is take your seedlings outside, in a protected, shady area for a couple hours a day and bring them back inside.
Eventually you take your seedlings out for the entire day, gradually exposing them to more sunlight and natural conditions, while still bringing the seedlings in at night.
After about 7-10 days of this, depending on the weather , you will likely be safe to leave your seedlings outside.
Step 12- Transplanting
With a little bit of luck, most of your seedlings will survive the hardening off process and will be able to be transplanted to your garden area, or into a pot within 10-14 days.
1. What are some of the easiest seeds to start indoors?
Vegetables like Broccoli, Brussel Sprouts, Cabbage, Tomatoes, Peppers, and Lettuce are great to start indoors. Flowers such as Marigolds, Zinnias, Alyssum, Morning Glory, Nasturtium, and Cosmos, Dianthus, Daisy, and Primrose are also great to start indoors. Many other vegetables and flowers work well with this seed starting method so feel free to experiment!
2. Do you need a heat mat?
No, the great part about starting seeds indoors using this method is you don’t need a heat mat. The closed domes along with the lights usually creates warm enough soil temps for the seeds to germinate. Even if your seeds are in your basement you should be able to get soil temps that are warm enough for seed germination without using a heat mat.
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RJ Caroff says
What temperatures work for starting seeds? My basement temperature drops to about 56 or 57 degrees in the winter and stays there until things warm up in the late spring. I’m assuming I would have to heat an area to start seeds? Thanks!
Those temps are actually ideal… don’t forget that under lights and with a humidity dome the potting mix temps are going to be higher. It’s really all about potting mix temperature, not air temperature. I’ve literally grown thousands of perennials from seeds in my unheated basement in New Hampshire
Thanks for the great info. I’m in Ohio so similar zone with you. I have a bulkhead door in my basement so will probably put seedling on the steps and open the bulkhead to harden off.
You’re very welcome Lou, glad you found this helpful! Bulkhead are great ways to slowly introduce seedlings to natural conditions. Makes things really easy to since you can leave the plants there and all you have to do is close the bulkhead!
I always wondered why my indoor seedlings got so “leggy”. I now realize it is either because I left them under the lights too long, or I had the lights too far away from the plants. This knowledge will really help my process because a lot of my seedlings were dying before. I also didn’t know about the hardening process. This is such a helpful article!!!!
I hate leggy seedlings! Probably the most frustrating part when growing indoors. Happy to hear this was able to help you out, thanks for taking the time to comment Justin!