AND TIPS TO AVOID THEM

Starting seeds indoors is necessary for many crops in our climate (zone 4 - 5) whether you grow them yourself or purchase them from a local farmer or garden store. This includes tomatoes, peppers, eggplant, broccoli, pumpkins, squash and many beloved annual flowers. Giving them a head start by growing indoors during the winter months ensures these crops will mature and produce within our short growing season.

While both an exciting and educational late winter hobby, growing starts at home is also challenging and requires a lot of attention and care. Unhealthy seedlings will lead to unhealthy plants that are more prone to pests, disease, and a poor harvest. Here are some common mistakes and tips to avoid them when starting seeds at home.

Too much water

While water is necessary for plants to survive, most plants prefer to have an opportunity to dry out their roots in between watering. Too much water leads to root rot, fungus and mold issues. Tender baby plants don’t have very many roots or leaves, so a little rot can be devastating. Keep these tips in mind:

Many seed starting kits sell a plastic dome to go over the growing container. This is only to keep the soil damp so the seed can germinate. Once the seed germinates (germinate means to put out roots and shoots), remove the plastic lid. Otherwise, there isn’t enough air flow and it creates too damp of conditions.
Before watering again, always test the soil moisture with your finger. If it feels damp like a wrung out sponge, you don’t need to water yet.

If you’re re-using plastic containers like yogurt containers etc. make sure to poke some holes in the bottom so the water can drain out of the soil.
Be careful to not wash away the seeds when watering. Water the soil well before you plant the seeds and then use a spray bottle to water until the seedlings are big enough to handle a gentle watering.
Finally, don’t let your seedlings and seedling containers sit in a tray of water for more than a day. Pour off any standing water and use less water next time.

growing seedlings in the Window Sill

Seedlings need 12 - 14 hours of light per day, so unless you have a greenhouse, you’ll need supplemental lighting at home.

Many people place their seedlings in a window sill because that’s where the natural light comes in. However, I don’t recommend doing that for a couple reasons. Window sills tend to be the coolest part of the house and are often drafty which can stress baby plants, which want a warm stable environment, like puppies, children and all baby creatures. Additionally, window light is not sufficient enough for healthy seedlings (more on that in the next section). Instead…

Set up a light and your seedlings on a table or shelf that isn’t directly in a window sill
Set away from drafts and heater vents, which can desiccate the tender leaves.
I know when I was living in an apartment, it was hard to find space that met all these criteria - as with everything, just do your best!

Inadequate lighting

This is the number one reason for leggy and unhealthy seedlings. Seedlings need 12 - 14 hours of light per day, which is impossible inside in Montana without supplemental lighting. Here are tips to ensure your seedlings have enough light to grow big and strong inside.

I highly recommend investing in a grow light which has a wide spectrum of blue and red light that promotes vegetative growth best.
Other options are fluorescent or LED lights - look for “blue” or “white” light. Avoid incandescent lights which produces a lot of heat and can toast seedling leaves.
Once you have a light, set it just 2 - 4 inches above your seedlings and adjust the height as they grow. If the light is farther away, the seedlings will start to appear leggy, thin, and stretched out, which we don’t want.
Evenly distribute the lighting across the growing containers or plant trays and/or rotate them every few days to keep the seedlings growing straight. Seedlings will start to lean and grow towards the strongest light source.

Thinning

Squash seedlings have just started growing their true leaves.

I always tell people to plant more than one seed per container to ensure that at least one seed will germinate. If you’re using old seeds, sometimes I recommend planting 3 or 4 seeds per container because seed viability wanes each year. More on seed lifespan and viability in this blog. However once a seedling is established, we don’t want more than one plant in each container (unless you have a very big container) because the two plants will end up competing with each other for space, nutrients, and light, which results in leggy, stressed, and unhealthy seedlings. This means, that you’ll have to “thin” or remove any additional seedlings. This is often hard for people to do who “don’t like killing plants,” but trust me, you have to in order to have healthy plants and a healthy harvest.

Wait until the seedlings have at least one set of true leaves.
Choose to keep the healthiest looking seedling. Remove any other seedlings so only one plant remains per container or cell.
Cut the seedling you want to remove with scissors or small pruning shears so as to not disturb the roots of the seedling you want to keep. Remember, seedlings don’t have many roots to spare, and they are very delicate.

Nutrient deficiency

Garden City Harvest’s Youth Harvest crew pots up pepper seedlings. Potting up means to transplant a plant into a bigger pot.

Without enough nutrients or space, seedlings become stressed and stunted — they may appear to stop growing or leaves might turn yellow and drop (this is also a sign of overwatering, so rule that out first). Usually after 4 - 6 weeks, most plants will need additional nutrients than what that small container of soil can provide. Additionally, starts may out grow their original container, requiring more nutrients and more space. Ideally, when they reach this stage, they can be planted outside; however, that’s not always the case. If your seedlings aren’t ready to go outside yet, there are two ways to give your seedlings more nutrients while they wait in pots.

Liquid Fertilizer

The first is using a water soluble liquid fertilizer, which usually needs to be diluted with water according to the directions on the bottle. I like fish emulsion because it’s high in nitrogen, which is exactly what growing plants need.

Water your plants with diluted fish emulsion fertilizer every other day or at minimum once per week until planted outside.

Pot Up

The second way to give your seedlings more nutrients (and space) is to plant them in a new and bigger container with new soil. This is something you should plan on doing for tomatoes, peppers, tomatillos, and eggplant since they are usually started indoors in February or March and not planted outside until the end of May.

Potting up means to transplant a plant into a bigger pot than the one it’s currently in.
As always when transplanting, water immediately after potting up.
Watch this video we made that shows you how to pot up tomato seedlings.

Learn more on potting up

Hardening Off

This is perhaps the most forgotten or overlooked step by beginners and yet the most crucial. Hardening off is the process of gradually acclimatizing indoor starts to outdoor conditions. A plant that has known the inside of a home or greenhouse its whole life can’t suddenly be expected to survive outside immediately. It will get sun burned, desiccated, blown over or broken by the wind, or simply freeze overnight in the cold. Here’s how to harden off starts:

Begin the process of hardening off a week or two before you plan to plant the starts outside.
The first day, set your starts outside in a protected spot for an hour. Check the weather and choose a mild day. Cloudy days are great, or set the starts in dappled shade where the sun is less intense. Water the starts and check back in an hour. Wind, sun, and outside air will dry starts out much faster than inside conditions.
The next day, leave them out for two hours, with about an hour of direct sunshine in the morning (morning sun is less intense than afternoon sun). Again, water them when you set them out and check back after an hour to make sure they aren’t wilted, flopped, or sunburned.
Gradually increase the length of outdoor time and direct sunshine over one to two weeks.
Once they’ve acclimatized to a full day outside, leave them out overnight as long as there is no danger of frost. (Watch the weather!)

Once you’re starts have adapted to living outside, they are considered hardenend off and ready to go in the ground.

Happy planting!

Note: Starts that you purchase from a nursery or Farmer’s Market have been hardened off already.

Common Mistakes When Starting Seeds Indoors