Starting Seeds Indoors

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seedlings in peat pellets

In December, the seed catalogues start arriving. I drool over new varieties and inventory the seeds I have that performed well last year. I can dream of spring, but the worst of winter is still ahead. In January, I place my seed order and by the time February rolls around, I have just about had enough of winter. I can tell by the angle of the sun, the blooming hellaborus, and the occasional mild day that spring is around the corner. We still have a couple of chilly months, but February means I can start seeds for our outdoor garden!

This is how a gardening addict gets through winter. Well, this and growing indoors hydroponically.

If you are new to starting your own seeds, have no fear! It is an easy and super fun project that is much cheaper than purchasing seedlings from the home improvement store. Follow these guidelines to ensure that your seed starting adventure will be successful and rewarding.

1. Determine what to plant and when

Once you decide which vegetables you would like to grow, you'll need to identify your growing zone to figure out when you should sow the seeds. For example, we live in Zone 7, which is green on this map.

Plant hardiness map growing zones

After you identify your zone, look up the first and last frost dates for your region. 

On your seed packets, you will find some instructions. These tell you when to sow the seeds with regard to the first and last frost. For instance, early spring crops like broccoli and cauliflower should be started indoors about 2 months before the last frost. Other plants, like root vegetables, do best if sown directly in the garden. Your seed packet will give you this information.

A few years ago, I discovered a handy trick. Within my iPhone, I have set up a calendar specifically for gardening with events that repeat annually. Each year, a notification pops up and tells me when I am supposed to plant something!

seed starting garden calendar smart phone

2. Choose your growing medium

There are many different vessels in which you can plant your seeds. Some folks use pre-made biodegradable pots, others make little pots from newspaper. You could also use a self-watering tray like this one. With any of these, you'll want a decent starting mix to fill them. 

For convenience, I like to use peat pellets. These nifty little things expand when wet and are both a pot and soil in one. 

 Peat pellets for seed starting
Peat pellets ready and waiting!


Soaking peat pellets for starting seeds
Starting the soaking process.


Expanded peat pellets for seed starting
Fully expanded and ready to go! 


3. Set up your seed nursery

If your house is chilly, you will want to place a warming mat under your seed tray to bring it up to the ideal temperature. Most seeds germinate best at >70°F.  

Place your pots or peat pellets in a tray and make sure they are thoroughly moistened. Ideally, you would have a clear dome to go over your tray to keep the heat and moisture in, but plastic wrap with a few holes in it will do. 

You will need a light source once your seeds start sprouting. A regular lightbulb will not have the spectrum of light that the plants need, and a sunny window will not have the light intensity required. I have tried to start vegetable plants without a grow light and learned my lesson! The result was weak, spindly plants that grew skinny and tall and flopped over under their own weight. We offer a few grow light options, but our favorite is this one

We built our own simple shelf to accommodate our little nursery (on the left in the photo below), but you can also purchase one like this that is ready-to-go.

seed starting shelf indoor hydroponic system

4. Plant the seeds!

Now that you have everything set up, it's time to plant! Most folks recommend making a few small indentations in each pot and placing one seed in each little hole. Cover with just a bit of soil or peat. Allow them to grow until an inch or so tall and then "thin" or remove the weakest plants. Keep them damp but not sopping wet.

Once they sprout and start growing upwards, vent the dome and then remove it when they are about a half inch tall. The seedlings will now need to be placed under the light. They require 12-14 hours of daylight and 10-12 hours of darkness (that's when they metabolize). We use a timer to make sure we don't forget to turn on and off the light. 

5. Transplant

If you started your seeds in a compartmentalized tray or in peat pellets, you will probably need to transplant them to larger pots as they grow (like these biodegradable ones) . Use a good quality soil mix and make sure they stay moist (but not soaking wet). If your soil mix does not have added nutrients, it is time to start feeding your babies. Remember to keep them under the light as well, but you no longer need that heat mat at this point.

6. Acclimation

Before the seedlings can go out to the garden, they need to be "hardened off". This is gardener speak for acclimated. Set your seedlings outside in a protected location for a few hours every day (unless the forecast calls for severe weather). Be sure not to place them out if the temperature is lower than their hardiness level (see chart below). Increase the amount of time they spend outside by a little each day. This allows the plants to adjust to temperature, wind, and light intensity so that they are not shocked when you plant them outdoors.

vegetable planting temperature chart
Image credit:

7. To the garden!

Once the danger of frost has passed and your plants have been hardened off, it is time to plant them in your garden! If you used peat pellets or biodegradable pots, you can bury the entire pot to reduce disturbing the root system.

If you are planting tomatoes, you should remove the branches from the bottom 2/3 of the plant and bury the main stalk so that just the top 1/3 of the plant is exposed. With most of the plant under the ground, it will develop a strong root system for a stable plant. 

If you can't wait until the last frost date, you could plant earlier, but you will want to provide protection in the event of a chilly night. These frost blankets will help protect tender young plants. If near freezing temperatures are forecasted, you can just toss them over the row in the evening and remove in the morning. 

Now sit back and enjoy watching your garden grow! Should any problems arise, visit our troubleshooting article for tips. Happy growing!

how to start vegetable seeds indoors