Starting seeds indoors 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.
Using this method, I start tons of vegetables from seed including tomatoes, peppers, cucumber, zucchini, lettuce, kale, green beans, and peas.
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 intense 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 sunlight.
Step 1- Buying Seeds
Take your time on this step. If growing vegetables or fruit, 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.
Step 2- Timing (When to Sow Your Seeds)
Once you’ve received your seeds, keep them in a cool, dry place until it’s time to sow them. Check the seed packet or catalogue to see if seeds need to go through a cold treatment such as vernalization, or stratification.
The next step is to figure out when to sow your seeds.
For Vegetables, Herbs, and Fruits:
Check out this 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 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.
For Hardy Perennials:
If you are sowing hardy perennials, you can a get an earlier start.
These seedlings can tolerate colder temperatures. They aren’t at as much of a risk of dying unless there is a hard frost (28 degrees or less).
For this reason, you can set hardy perennial seedlings outside about 2 weeks earlier than your last frost date. This means you can start them indoors 2 weeks earlier as well.
Let’s look at an example:
You purchase some Blanket Flower seeds.
After doing a Google search you know that you should ‘sow indoors 6-8 weeks before last frost’.
You are in New Hampshire (zone 5) and the last frost date is usually May 15th.
Count back 2 weeks before your last frost date which gives you a date of May 1st. This is the date you can safely put hardy perennial seedlings outside.
Simply count back 6-8 weeks before May 1st and this is when you want to start that packet of seeds. In this case it would be around March 13th.
Step 3- 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 4- 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 5- Sow Seeds
For larger seeds plant 1 seed per cell.
For small 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.
Do your seeds need light to germinate?
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 6- 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 7- Water Trays
Fill each tray to the top with water. Wait 10 minutes as the potting mix soaks up the water, then add one inch of water to the tray.
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 8- 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 9- 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.
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 10- 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 11- 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.
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