How to start vegetable garden seeds indoors is one of the most common questions I hear from new gardeners every spring. I’ve experimented with various methods to grow garden seeds indoors so today I’m going to show you the method I’ve been using for several years.
Starting your own vegetable garden seeds indoors is a fun project and a way to get a jump start on the gardening season. It also can save quite a bit of money in the long run if you don’t have to buy vegetable garden seedlings from the local garden center.
At our old homestead, I grew seedlings in my greenhouse. Unfortunately I had to leave my beloved greenhouse at our old homestead when we moved in the middle of the winter.
I currently don’t have a greenhouse so we’ve been starting seeds inside our house the last few years. My kids love to help start our vegetable garden seeds indoors every spring. Sometimes this results in seeds getting planted a bit too close together but that’s ok, we just thin them out or transplant them later!
How to Start Vegetable Garden Seeds Indoors Without Grow Lights
Call me old fashioned, but I’ve never used grow lights to start my garden seeds indoors. I prefer good old all natural sunlight and it doesn’t cost me a cent!
That’s not to say that using grow lights is a bad thing. It definitely isn’t bad and can actually be really effective if done correctly. It’s just not my preference. Here’s an article from Grow a Good Life if you want to learn how to start seedlings indoors with a grow lights.
To start vegetable garden seeds indoors without grow lights, you need a window that receives 6+ hours of direct sunlight per day. The best location is a window that faces south. We don’t have any south facing windows on our homestead but we have a giant window in our dining room that faces southwest.
This giant window has a deep windowsill perfect for holding seed starting pots and plants. This window does not receive direct early morning light, but by mid day it starts to capture some of the suns rays. The sun in the mid to later part of the day is actually really quite bright, intense and warm making it the most ideal spot in our house for us to grow seeds indoors.
The Best Way to Start Vegetable Garden Seeds Indoors
1. Select seed starting pots
Here’s our list of 20 Free DIY seed starting pots to give you some ideas. When I was growing up, we bought this style of seed starting trays that acted like mini-greenhouses and reused them each year. After experimenting with various types of seed starting pots over the years, I figured out that my favorite seed pots to use to start vegetable garden seeds indoors mimic the mini greenhouses we used when I was a kid.
My favorite seed starting pots are the plastic lettuce containers with the fitted lid from the grocery store. When used as a seed starting pot, these lettuce containers act like a mini greenhouse to hold in moisture and warmth which really helps the seeds germinate. Once the seeds sprout, I take the lids off.
I use the plastic lettuce containers for seeding plants that I know will need transplanted and don’t mind a little root disturbance, like tomatoes and peppers.
For plants that dislike root disturbance like cucumbers and pumpkins, I plant them one seed per seed pot or paper cup and not in big trays all together.
2. Fill the seed pots with soil
Selecting a good seed starting soil mix is key to growing healthy seedlings. Just like when you’re building a raised bed vegetable garden, it’s important to use the correct type of soil for your needs.
When I had my greenhouse at our old homestead, I mixed up big batches of my own seed starting potting soil following this tutorial on the Garden Betty website.
Since I have less space in my house than in my greenhouse to start seedlings, I need less potting soil. Now I just buy a bag of high quality seed starting mix at the local garden store every couple years.
3. Plant the seeds
Read the seed packet to find out how deep you need to plant your garden seeds. For seeds that need a very shallow planting depth, we find it is easier to lay seeds on top of the soil in the pot and then sprinkle a thin layer of soil on top of the seeds to reach the correct planting depth.
For vegetable garden seeds that need more depth when planted, you can use a pencil or stick to poke a hole or draw a shallow trench in the soil to the depth you need, plant the seed and gently push the soil back over the hole.
4. How to water seeds and seedlings
We use a spritz bottle like this to water our seed pots (we bought a bulk pack since we also use them for our homemade all purpose citrus cleaner). This helps to ensure that the soil stays damp enough but doesn’t flood the pot of soil.
It’s important to not let the soil dry out while seeds are germinating. I have an alarm set in my phone to check our seed pots every morning and water as needed.
5. Monitor sunlight
Place your seed starting pots or trays in a warm, sunny spot. Our sunny window is directly above a heater vent so even on cold mornings, the seed pots are warmed by the air coming out of the heater.
If you have a sunny window to place your seed pots but it’s not a warm location, you can use a seedling heat mat like these to place under your seed starting pots.
Monitor the seed pots daily and watch for growth. It’s so exciting to see the first seeds sprouting up through the soil!
You may have heard of people talking about seedlings that get “leggy”. This means that a seedling or plant that is stretching too much and too far for sunlight grows a plant that has an overly long stem that looks like long legs, hence the term “leggy”.
Seedlings will grow towards the sunlight, a fact that is fascinating to watch. If you look at your seedlings daily, you will notice their growth towards the sunlight.
To try and balance out this directional growth, I turn my seedling pots everyday when I check their water level. If the seedlings start off the morning leaning towards one direction and you rotate them, by the end of the day the seedling will be growing the direction towards the most sunlight. Fascinating!
6.Transplant seedlings as needed
If you planted one seed per individual seed pot, you probably won’t need to do any transplanting until your seedling is ready to plant in the garden.
Some of our seedlings are started indoors well in advance of when they can be planted outside due to our short growing season. These seedlings will need to be transplanted into larger pots as they grow.
The tomato and pepper seedlings we planted indoors in early March will need to be transplanted. These seedlings will likely need to be transplanted another one or two times by the time they can be planted out in late May/early June depending on how warm or cool a spring we are having.
7. How to harden off seedlings
Before you plant your seedlings outside, they need to be hardened off. This means the seedlings need to be slowly transitioned from the warm temperatures of your house or greenhouse to being acclimated to the cooler weather outside.
I start this process a week before I plan to plant my seedlings outdoors in the garden. I start off with putting the seedling pots outside in a protected spot out of direct sunlight once the day warms up over 45 degrees.
The first day I put the seedlings outside for about two hours. Then I gradually add more time each day until the seedlings are out all day. After day three, I put the seedling pots in a location where they will receive morning sun but not direct sun at the heat of the day. Too intense sun exposure on seedlings not properly hardened off can cause the seedlings’ leaves to be sun scorched.
After day five or six, I start to put the seedlings in direct sunlight. By day seven, I start to leave the seedlings outside overnight if the temperature does not get below 45 degrees. If it is too be slightly cooler than that, I put a piece of garden row cover over top (I use row cover for so many things in the garden!) If the temperature is to be close to freezing or below, I put the seedlings in our cool vegetable storage room overnight.
Once the seedlings reach the point of being acclimated outside 24 hours per day, then they are ready to plant in the garden.
Be mindful of where you put your seedlings to harden them off. In 2020, I put several trays of seedlings outside to harden off. I sat them in an antique Radio Flyer wagon thinking that having them slightly up off the ground would prevent them getting trampled by our dog.
I made the mistake of leaving our seedlings in the wagon while we were away from home for a couple hours. When we came home, we discovered that a couple rascally chickens had hopped up in to the wagon and ate all of the seedlings!!
I was devastated. All that hard work of starting those seeds, tending to them daily and nurturing them with such love and care. The only bright side was that our chickens laid some really good eggs in the next day or two!
When should you start vegetable garden seeds indoors?
The timing of when you should start to plant vegetable garden seeds indoors will vary according to your climate and growing season. The timeframe that works for us in a cold, northern growing season in Montana is going to be very different than the seed starting timeframe for someone living in a warmer southern climate.
To determine the best time to start your garden seeds indoors, read our article on when to plant vegetable garden seeds. This article contains everything you need to do to figure out your growing zone, first and last frost dates plus a handy free printable resource to help you determine the best time to plant garden seeds specific to your climate and growing zone.
As an example, I wrote in our article about how to grow a salsa garden, that I start our vegetable garden seeds for tomatoes, peppers and onions indoors in March. This ensures our plants have enough growth time in our gardens during our short growing season in Montana so we can harvest the homegrown ingredients needed to make and preserve our delicious garden fresh salsa.