How to Start Seeds Indoors

How to start seeds indoors - no need to buy transplants when it's time to plant your garden.

How to start seeds indoors without a greenhouse

This post was updated in January 2021

I really want a greenhouse. A greenhouse or a high tunnel, either one. Or a sunroom attached to the south or west side of the house, somewhere I can start seeds early in the season. And to sit in during the winter when it's cold and I want to be "outside."

I've even collected a few windows here and there, and the glass door we replaced on our home a few years ago, but I don't have enough to build my own greenhouse.

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And I'm even jealous of the cute home-built greenhouse that came with the house our youngest daughter and son-in-law bought. But instead of growing things in it, it houses their kids' outdoor toys.

"No, no!" my heart cries out. "You need to have plants in there!" Oh well, maybe in the future when the children are older she'll discover that she likes growing things. Or maybe not.

If your heart cries out for a greenhouse too you'll be glad to know that you can start seeds inside your home instead. It really isn't that hard, although you might have to rearrange the furniture.

We just have to be be a little more creative when it's time to plant seeds indoors. Let's brainstorm about seed-starting locations and a few methods of starting seeds.

In case you're wondering, the high tunnel in the photos in this post belongs to a friend of mine. She got it through an NRCS grant program.

Grow your own garden plants from seed even if you don't have a hoop house or greenhouse.

Starting seeds indoors

Start by assessing the places inside your house that might work.

For instance, we have house cats, and one feline in particular likes to munch on green things. And knock over containers. And dig in the potting soil. 

I used to grow seedlings on the kitchen counter, but I had to find a new location when Thor came to live with us. He's not allowed on the counters but I regularly find him up there. (And I'm not happy when I find him up there!)

Which means my seed starting containers have to live in one of the extra bedrooms, where the door is closed to keep the cats out.

Keep your seeds warm so they'll sprout

Warmth is more important than light when you first start your seeds, so find the warmest spot in your home for your seed starting containers.

A seed starting kit with a plastic dome on top is an excellent way to start your seeds. The dome will not only keep cats out (ahem) but it also increases the humidity, which sprouting seeds appreciate. 

If your seed-starting location is a bit on the cool side you can purchase a seedling heat mat to use underneath the seed-starting trays.

While seeds don't need light at first, as soon as the sprouts appear they'll start reaching toward the light, so you'll need to move them to the sunniest spot you can find. 

You should also remove the plastic dome at this time, if you're using one. Too much humidity can cause mildew or fungal problems.

Find the brightest light for your seedlings

If you have a south- or west-facing window - and no plant-eating cats around - plan to house your seedlings there. I moved a card table in front of my southwest-facing bedroom window to hold my seed starting trays.

Of course, if you live in the southern hemisphere, you'll want to use a north-facing window instead, if you have one.

Seedlings require a lot of light to keep them healthy and prevent them from becoming leggy. If you need more light, you can augment what you have with mirrors. Thrift stores and yard sales are great places to buy inexpensive mirrors, by the way.

Simply place a mirror behind the plants, so that the window is in front of the plants and the mirror is in back, with the plants in the middle. The mirror will bounce the light around and illuminate the plants from both front and back.

Additional mirrors could be placed on either side, so that the plants are surrounded by mirrors on three sides with the window on the fourth side. Or cover sheets of cardboard with shiny aluminum foil if you don't have enough mirrors available.

Using grow lights

If you have a less-than-perfectly-placed window, you can use grow lights to boost the light.

Regular shop light fixtures with fluorescent bulbs will provide plenty of light, or you can buy grow light bulbs.

You'll need to raise the lights as the plants grow upward. 

If the height of your light fixtures isn't adjustable, you can adjust the trays' height instead. When the plants are tiny, place them on top of something to bring them up closer to the lights. Then move the plants down as they grow taller instead of moving the lights up.

Unusual DIY greenhouses and heating methods

Still wishing for a greenhouse? Maybe it IS possible.

Over the years I've found some innovative ideas for home-made greenhouses, hoop houses and other structures, as well as how to keep the plants inside them warm.

My gardening friend with the drool-worth hoop house in these photos uses a heated above-ground swimming pool to provide warmth for her plants. (And for an occasional winter swim too!)

Other methods of heating include:

- Composting inside your hoop house
- Housing chickens or rabbits inside a hoop house
- A concrete or brick floor will capture the sun's heat during the day and release it at night
- Water barrels (often painted black) inside the greenhouse will also capture and release thermal heat

Another homesteading friend and her husband built a lean-to greenhouse on the south side of their home. The structure was made of 16'x4' wire cattle panels (also called utility panels) with a short end on the ground and the other attached under the eaves of their home, then covered with greenhouse plastic.

The panels are sixteen feet long, so they were bent into a curve. They were attached to each other along the long sides, and formed a "room" alongside their home. Now that I think of it, it was sort of "half a hoop house" or a half dome shape.

By opening the windows between their house and the hoop house in the winter, these homesteaders took advantage of their wood stove's heat to keep their plants warm.

I bought a goat from another homesteading family who built an in-the-ground greenhouse attached to their storm shelter.

They'd excavated right next to the shelter and poured concrete for the floor and walls that went several feet deep into the ground, with concrete stairs at one end.

This "hole in the ground" was topped with a metal frame and glass windows that let the sun shine in. The greenhouse addition was the same size and height as their concrete tornado shelter, which made it attractive as well as functional.

Plants lined the shelves they'd built along the back wall. On particularly cold nights they used heat lamps (the kind used to keep chicks warm) to keep the space above freezing.

Even without a greenhouse you can start seeds early in the season. No need to buy transplants when it's time to plant.

Starting seeds outdoors

Can't you just start seeds outdoors instead? Sure, depending on what plants you want to grow and where you live.

Cold weather crops can be planted directly in the ground and most of them can withstand a light frost.

You'll find some ideas and inspiration in this post on how to grow food in as little as 3-4 weeks and in this post on growing looseleaf lettuce.

If you need to buy seeds, keep reading for the source I use and recommend.

Cold weather crops 

In general the following seeds can be planted outside around the time of you last average frost date (but check your seed packets for specific details):

Brussels sprouts
Chinese cabbage
Collard greens
Mustard greens
Onions *
Swiss chard

*Onions are usually planted as sets or as plants.

Warm weather crops 

These vegetables are best started indoors as seeds. They can be planted outdoors after all danger of frost has passed. In general, wait until the temperature is above 70° to plant these seeds outdoors or to transplant them into the garden.

Corn *
Sweet potatoes **

*Corn doesn't transplant well and should be planted directly in the ground.

**Sweet potatoes are grown from slips, not from seeds. Learn how to start sweet potato slips at home, to transplant outdoors when it's warm enough.

Warm weather vegetable plants take much longer to mature and bear fruit (or rather, vegetables), which is why many gardeners start their seeds indoors as much as six weeks before the ideal planting date - or buy already-started transplants from the nursery.

If you live in a place with a short growing season, you might not have time for some of these plants to produce before your first frost arrives, so choose short-season varieties and/or start your seeds indoors so you'll have a harvest before your season is over.

Frost protection

If you're expecting a late frost and have already planted your warm weather plants outdoors, you can cover them to help keep them warm. 

Turn a glass canning jar over each plant if they're small. Plastic gallon-size milk jugs can also be used by cutting off the top and turning it upside-down to cover each plant, or cutting the botom off and setting the top portion on top of the plant. These are called "cloches."

Cover the plants with a "low tunnel" of frost-resistant fabric, which is also called floating row cover or frost blanket. 

You can see a picture of and read about the homemade low tunnel that I put together for my cabbage plants each year, although it's covered with a insect-resistant mesh rather than frost-resistant fabric.

Or build a cold frame over the plant bed by surrounding the bed with straw bales and cover the top with re-purposed windows or plexiglass.

If you use any of these methods, be sure to uncover the plants before the temperature warms up so you won't "cook" your young plants. The heat will build up in there quite fast.

Where to buy seeds

Seeds are selling out everywhere this spring. Gardening is enjoying a resurgence in popularity and I am thrilled! I love to see people interested in getting back to the basics and learning old skills.

However this means that the major sources of seeds are selling out online and in stores, and it's harder and harder to find seeds right now. 

By the way, did you know you can save extra seeds that you have left over this year for planting next year? You can!

Smaller seed sellers might be the best way to find what you're looking for. I recommend Mary's Heirloom Seeds, a small company that carries over 700 varieties of open-pollinated, heirloom, non-GMO seeds. I've always been happy with the service and the quality of seeds I've purchased from Mary.

If you'd like to know more, Mary wrote a guest post here on Oak Hill Homestead several years ago. Read more about Mary's Heirloom Seeds here.

Need more resources?

If you'd like more information on starting a vegetable garden, here's how to turn your garden dreams into realityhow to order seeds and how to build a raised garden bed even if you're not a master builder.

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You might think all is lost if you don't have a greenhouse. Here's how to find the best location for starting seeds inside your home, plus some DIY greenhouse alternative ideas.
This post contains affiliate links. Read my disclosure here.

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  1. Wow, super helpful post. Especially for beginners. Great read!!

  2. All really great tips! Thanks for sharing this with us at the Homestead Blog Hop, please come back again soon!


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