Winter in our area isn’t over yet. The last frost day is still a few months away. But spring is coming and with it the next growing season! Starting seeds indoors is the start of it.
When we say starting seeds indoors it doesn’t mean in the house (even though it can be that), but in an enclosed environment that is best for the particular seed we are starting.
Why start seeds indoors?
We mainly start seeds indoors because of our short growing season. This way we can extend the season upfront. While it is still snowing outside, we grow young plants inside to transplant into the garden as soon as the weather conditions are right for the particular plant.
Growing plants from seeds is a lot of fun. I am always amazed at how out of a dry little something (seed) a new plant grows and produces delicious fruits that contain the same seed to produce new plants.
Starting plants from seed also saves money. It isn’t a lot of work, but you can start a lot of seedlings yourself for the price of buying one plant.
The best place to start seeds indoors
We said in the spring starting seed schedule article, that you have two options when starting seeds indoors, add more time, meaning starting seeds very early, or you can create better-growing conditions, so the seeds germinate and grow fast. We aim for the latter. For any given plant variety we want to create optimal growing conditions.
Not all seeds are best to start in a warm house, depending on the climate a propagating greenhouse or even a cold frame might be a better option since it also has more optimal light. The idea is to have a place that is sheltered and somewhat warmer than the outside, to get a head start for seedlings.
In our cold climate (Zone 3) seeds can be started in all of the above and even outdoors by using winter sowing, (follow the link to read more about that). Winter sowing works great for cool-weather plants like cabbage, lettuce, and other greens. If you only have limited space indoors, move all the cool weather crops outside. In our seed starting schedule, those are all the plants that can be planted out before the last frost date.
For heat-loving summer crops like peppers and tomatoes, a warm and sunny location is best. We will talk more about supplemental light below.
What do you need to start seeds indoors?
Seed starting pots or propagation trays come in all shapes and sizes. If you want to avoid plastic you can build your own pots out of newspapers or avoid pots altogether by using a soil block maker. There are also peat moss pots available, but from our experience, they don’t work so well. Maybe because our climate is too dry.
We use small planters (often recycled from plants we have bought here and there) for plants that are not staying inside long: like cabbage, onions, or lettuce.
For peppers and tomatoes, we mostly use the (free) yogurt containers. It seems like they have the optimal size for those plants and save me some replanting work.
Recycled toilet paper tubes make great planters for cucumbers. They can be planted with the seedling into the ground, so you don’t disturb the roots.
For squash and bigger plants, we use a bigger container so that the roots have more room to grow and are not disturbed by transplanting.
Propagation seed starter trays are great if you just want a start on plants like lettuce, chard, beats, etc.
As in most cases with gardening, we encourage you to keep things simple and achievable. Plants will grow in whatever pots you start them in. If you want to be specific, you can, but there is no real need for that.
The one thing that we would recommend is sturdy planter trays. They do make life easier to handle many seedlings at once.
You can grow microgreens in them in winter, so it sure is worth it to have them.
– Potting soil
The seed starter potting soil is important. You want good light soil. Special seed starting mix or soil that is very fine and sterilized might be important for some seeds that are very small. For most vegetables, it is not needed.
Make your own soil, Mel’s Mix from the Square Foot Garden book. Mix together: 1/3 compost, 1/3 vermiculite, and 1/3 peat moss.
You can find all of these ingredients in a garden center or Home Depot. Read more about the DIY container soil here. This is our favorite soil to use, it is not as high in peat moss as ProMix, and much higher in natural compost. Lately, though it has been harder to find natural bug-free compost.
Even though we don’t recommend using enriched potting soil, it often is the only soil that is widely available. The chemical fertilizers only give the plant a speedy start, but then the plant tends to ask for more. We do use it if we don’t find all the ingredients for Mel’s Mix.
For sowing seeds in seed trays to prick them out later, you can use vermiculite instead of soil. We have a whole blog post about it, to learn more go here.
Labeling is important so you know what varieties you are actually growing. It does not matter what kind of labels you use. Garden labels are great, but a plastic spoon works just as well. To avoid plastic, you can use wooden labels, unless you make your own, you will spend more money though since they don’t last as long as the plastic labels do.
Also, a garden notebook is a helpful gardening tool, here is how to make your own.
– Heat Mat
As we already mentioned many seeds need warm temperatures to germinate, so find a warm spot in your house. The top of a fridge would be a better place than a cold but bright window. Placing the tray on top of a heating vent in the winter is great too. You want about 85F degrees for fast germination. A Germination Station with Heat Mat can be helpful.
After germinating not all seedlings like it warm. Winter crops like the cabbage family plants, like it rather cool. We find they do better in a sunny basement window or out in the garage greenhouse. Or use winter sowing for cold-weather crops.
– Grow lights
For germination, a seed needs moisture and nice warm temperatures, but not so much light. As soon as the seeds are up, young plants need a lot of light.
Starting seeds later in the season (see the planting schedule), helps with better light conditions, so that you might not require any grow lights. A south-facing window might be all you need.
Whenever possible we recommend using a sunny window, since a grow light is more comparable to a cloudy day than to direct sunshine. To imitate sunlight, you will need expensive grow lights that can make growing seedlings not worth the cost.
But if your spring is mostly cool and overcast, or you do not have good south-facing windows, adding grow light might be essential. East- or west-facing window would be better with supplemental light. T5 lights work well as supplementary lights, LED lights are more energy efficient. A north window is not a good choice for seedlings.
Fill a container with soil and compact it down slightly. You want your container to be filled without air pockets, but also not too compacted. If the soil is dry, now is a good time to water. Make sure the soil is moist before planting the seeds.
We usually do not sow seeds in seed trays to prick them out later, it’s just one more step of work, and why do more if you don’t have to? But it is an option too.
Plant seeds no more than 3 times their size deep. Since we are indoors, they can be planted even more shallowly. Only peas and beans do better well covered. But we usually don’t start them indoors anyway.
Plant 1-3 seeds for plants that grow best alone, like lettuce, tomatoes, and cabbage. Once the seedlings are up and growing, thin them out to have just one plant. See also what to do with multiple plants in one seedling for more options.
Onions, beets, and radishes love growing together as a cluster, you can start 4-6 seeds in one pot of them.
After the seeds are covered spray them with water. In our dry climate, we also like to cover the pots with plastic wrap to keep moisture.
We have a separate post for starting tomatoes from seeds, and we save ourselves even more transplanting work.
Do you like to start your plants from seeds or would you rather buy seedlings? Please let us know in the comment below.