How to Successfully Start Seeds Indoors
If you’ve ever tried to start seeds indoors to get a jump on the growing season, you know how frustrating it can be trying to get it just right. So we put together this video tutorial to show you exactly what to do (and how to do it correctly) to start growing seeds indoors.
More Seed Starting Resources
Below is a download showing you when to start planting different types of seeds. It’s a handy guide that’s based on the expected last frost date in your area.
We also have for you an easy-to-follow written guide on when to start what.
Why start seeds indoors?
Some plants, such as tomatoes and peppers, prefer warmer weather and generally won’t germinate until the ground is warmer. By starting them inside, they’ll begin growing much sooner.
Sometimes, you want to start harvesting veggies earlier or getting blooms earlier in the season so you’ll start seeds indoors.
When should you start seeds indoors?
The right time to sow seeds depends on the expected last frost date in your area. Start them too early and they’ll be leggy and overgrown by the time it’s warm enough to transplant them outdoors. Start them too late and you might as well just buy the plants from your local garden center.
What do you need to start growing seeds indoors?
There are a lot of kinds of seed starting mixes, many of which work quite well. We tested many different options looking for the best one – you check out our review of different seed-starting mixes here.
Never use garden soil for starting seeds. We don’t recommend potting mix either, as it is not an optimal growing medium for starting seeds (but if you transplant seedlings into larger containers before you move them into the garden, then potting mix is a good option at that time).
In this video we used Coast of Maine’s Sprout Island Organic Seed Starter mix (it’s my personal favorite and a top performer).
Seed starting mix is dry so you need to moisten it before use. Using a trug (like this Heavy Duty Recycled Rubber Trug, 8.7 Gallon or any kind of large container) fill it with seed starting mix and add water until the mix is nice and moist. This is preferable to just adding water after planting, as the moisture won’t reach parts of the growing mix.
If water comes out when you squeeze the seed starting mix – it’s too wet
If it doesn’t hold together – it’s too dry
Something to plant them in
You can start seeds in anything that will hold the growing mix and stay moist – including yogurt cups, plastic containers, egg cartons, milk jugs, paper pots, peat or cow pots, and many more. Just make sure that they are covered to retain moisture while the seeds are germinating, that there’s a waterproof tray or surface underneath and that you are watering them from the bottom.
You can also buy inexpensive plastic trays with greenhouse covers at most garden centers and hardware stores. The cover is important to keep the soil moist. You can also use a plastic bag or cellophane wrap.
There are self-watering systems if you, like me, forget to water your seeds. These come with a watering tray and seedling tray (typically with between 12 and 24 cells). A platform goes in the bottom of the watering trays so the planting tray isn’t sitting in water. There’s a capillary mat that wicks the water from underneath up onto the surface of the platform, and from there the seed starting mix grabs the moisture (I buy it in 3yd rolls and cut it to size as needed).
I feature several in the video, including the Deep Root Seedstarting System from Gardener’s Supply. I like the larger cells, as you don’t have to seedlings into larger pots as they grow.
Another one I use is the GrowEase Seed Starter Kit, also from Gardener’s Supply.
Also shown is a self-watering system that has a water level indicator, so you can see when more water is needed.
I also show the Biodome cover from Park Seed – it has vents so you can control the ventilation.
Make sure all of your pieces are cleaned before use!
The easiest way to provide supplemental heat is with a seedling heat mat. It is not waterproof, but it is water-resistant so you can get it wet. It heats up to about 85 or 90 degrees, heating up the seed-starting mix so seeds can more easily germinate.
The seed-starting heat mat featured in the video is 20″ x 48″ and costs around $35 on Amazon (there are many brands but they’re all similar), but there are mats in a variety of smaller sizes that cost less. If that’s out of your budget, there are other ways to create heat for your seeds.
- Put them in a warm closet (most seeds don’t need light to germinate)
- Top of the fridge
- Besides a computer or tv (carefully!)
- Use a metal tray or shelf with a 40W incandescent light bulb underneath. LED won’t work because it doesn’t give off heat.
What about by a sunny window? We don’t recommend that, as the window will get cold at night.
Now, add the seed starting mix!
Take the pre-moistened mix and fill the tray. Don’t pack it in, just lightly place it in. Push down the center to make sure there are no air pockets, and then fill once more with the mix. Don’t pack it in, just flatten it out.
Add the seeds
Seeds packets should tell you on the back how long it takes the seeds to germinate, as well as other useful information. Some provide a ton of helpful info, including Renee’s Garden Seeds (they have a flap on the back with extra details) and Botanical Interests (although most of the information is inside the packet so you have to cut it open).
For small seeds, you’ll just want to lightly cover them; larger seeds can be pressed down into the growing medium. See the seed packet for specific details.
For the peppers I feature in the video, I put two seeds in each cell. For larger plants, you might want to stick with one. By sowing two per cell it increases the chances that each cell with have one seedling. If two germinate then I pinch out the weaker one.
Label Your Seeds
Don’t forget to label when you plant or when the seedlings emerge you won’t know what’s what! There are lots of options for seedling markers/labels, and lots of sizes available. Most are quite inexpensive, like this one I use. Make sure that you’ll have enough room for your greenhouse cover. Write the name of what you’re planting in an ink that won’t fade or use a pencil.
Lightly mist the surface. It should not be wet, just moist. Add the lid.
Don’t water from on top. The seeds might wash away, or the seedlings will break. You also can’t tell how much water you’re adding when you add water from the top, which can contribute to fungal problems.
If you’re not using a self-watering seed starting kit, fill the watering tray a quarter of the way up the cells every time you water. If, after 15 minutes, there is still water, pour it out.
And that’s it for sowing seeds indoors! Watch the video for full details.
Next up … see our video on what to do when seeds germinate.
Check back for when we post the video from after the seeds germinate! Or subscribe to our YouTube channel to know as soon as we publish our videos!