How to Start the Best Seedlings Indoors for Your Garden

How to Start the Best Seedlings Indoors for Your Garden

How to Start the Best Seedlings Indoors!

Starting your own seeds indoors is a great way to b more self-reliant and save money on your garden! This project gives you control over the fertilizers, pesticides, and potting soil used. Starting from seeds also gives you a huge number of varieties to choose from instead of just two or three varietes offered at the garden center.

You also have complete control over when you start seedlings. This gives you the option of starting cool-season crops early enough to get an extra harvest in the spring!

Learn How to Set Up a Seed Starting Calendar to track when to start your seeds for the best results.

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I’ve been gardening since I was 3…I still remember helping my Dad plant bean seeds in our garden as a little tyke. I began growing my own seedlings in windowsills in the spring then created an easy seed starting set up that I also use for growing microgreens in the winter.

I also know what it takes to start seedlings on a commercial scale from my education and work in the horticultural field.

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Mary's Heirloom Seeds offers a wide variety of seeds... Start the Best Seedlings Indoors for Your Garden

Why Start Your Own Seedlings?

There are many reasons that gardeners decide to start their own seedlings in a sunny windowsill or under lights in the late winter and early spring.

  • Save money
  • Reduce environmental impact
  • Control over pesticides and fertilizers
  • Plant a wider selection of varieties
  • Green therapy!
  • Grow microgreens

Save Money By Starting Your Own Seeds Indoors

The cost of greenhouse production is enormous. Besides the investment in the facility itself, there are costs for heating, cooling, watering, chemical applications, labor, growing medium, seeds, containers, and transportation. Once the flats reach the retail nursery they still need to be cared for – more labor. Plus, everyone wants to make a profit off those little plants. Of course, you pay for all of that when you buy seedlings.

There are expenses involved in starting your own seedlings indoors. You’ll need grow lights, extension cords, a power strip, and a timer, plus a shelf or table for your setup. If you travel or are super busy, it might be better to just purchase your seedlings. However, the cost of one packet of seeds is usually about the same as one 6 pack of small seedlings or 1 pint-sized start. So you really can get a lot more for your money with this DIY project.

A popular non-organic fertilizer...I don't think this color occurs in nature.
A popular non-organic fertilizer…I don’t think this color occurs in nature.

Control Over Fertilizer & Pesticide Application

You might be surprised at the volume of non-organic chemical applications used to produce those gorgeous flats of veggie and flower starts in commercial greenhouses. There are insecticides, fungicides, miticides, fertilizers, and hormones for regulating growth.

Some of the insecticides applied are systemic, which means that bees and butterflies are poisoned by the nectar from treated plants. Systemic insecticides are transported through the entire plant and none of this is listed on the label when you buy seedlings

How to Start the Best Seedlings Indoors for Your Garden

Steps to Start Your Own Seedlings

This project might seem overwhelming at first, but if you take it step by step you’ll be off to a great start! Let’s begin with what you need for your indoor seed set up.

  • Seeds
  • Growing medium
  • Containers
  • Lights
  • Miscellaneous (seedling heat mats, labels, fan, plant mister)

What Kind of Seeds Should I Buy?

There are so many choices – heirlooms, hybrids, organic. What should you buy? If you want to…

  • save seeds from your plants for next year, choose heirloom or open-pollinated seeds.
  • to grow the biggest tomato or most disease-resistant pepper, hybrids may suit your needs best.
  • be sure that your seeds have not been treated with fungicides, choose organic.
  • save money on food, choose seeds for crops that you enjoy growing, eating, and preserving.
  • get the best results, find out what varieties do well in your growing conditions.
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Fast growing greens, like spinach, can be direct seeded into your garden.
Fast growing greens, like spinach, can be direct seeded into your garden.

Should You Start All of Your Seedlings Indoors?

You probably won’t want to start all of your seedlings inside. Many crops do best when direct seeded into the garden. These include root crops, beans, peas, and corn. Some crops grow so quickly that you probably don’t need to plant them inside.

Start enough plants to fill your needs.
Start enough plants to fill your needs.

How Many Seedlings Should You Plant?

Figure out how much space you have for your favorites and how much you are likely to use before you plant an entire packet of eggplant. If you only like a little, don’t plant a whole flat. I still have trouble with this part, so don’t feel bad if you end up with more than you need! You can give some to neighbors.

The back of the seed packet usually has information about when to plant.
The back of the seed packet usually has information about when to plant.

When Should I Plant My Indoor Seeds?

This will depend a great deal on the type of seed and where you live. Start by checking the USDA Zones to find out the average date of the last spring frost in your zone. Mark the date on your garden calendar. (Be aware that this is the average date of your last frost, it will vary from year to year.)

Now, look at the seed packets for information. The packet shares a range of how many weeks before the last spring frost you should start the seeds. Count back on the calendar and make a note to start the seeds on the appropriate date.

For more information, check out my post How to Set Up a Seed Starting Calendar!

Picking the Best Potting Soil

Many people like to bring in some garden soil to start their little plants. If you do this, make sure you sterilize the soil to kill any pathogens that cause disease. Sift the soil through a screen and dampen (you don’t want it soaking wet). Spread the soil in baking pans and cover with foil. Place in your oven at 250 F and bring the soil temp up to 180 degrees F for 30 minutes. Be aware that the scent is kind of funky.

I prefer to use a growing medium that contains no soil because it drains better. You can purchase a ready-made mix, or make your own with 1 part finely milled peat moss, 1 part sterile compost, and 1 part vermiculite.

Coir is an environmentally friendly alternative to peat moss. I’m avoiding the use of peat moss because the peat bogs are home to endangered species. If you choose coconut coir in place of peat, you need to rinse it thoroughly 2 or 3 times before planting seeds.

Composted leaf litter is another great substitute for peat moss in your seed starting medium. You have a lot of leaves you can save money by making your own potting ‘soil’.

Check out How to Start Eco Friendly Seeds!

Seed starting trays

Choosing Containers for Starting Seeds

There are many kinds of containers for starting your little seedlings. It’s important to make sure they are clean (sanitize with mild bleach solution) and have drainage holes. You can use peat pots or pellets that can be planted along with the seedling. Mini greenhouse kits are also available. They look like the flats seedlings come in and include a transparent lid for retaining moisture.

Recycled containers (plastic yogurt containers, the bottom half of milk cartons, plastic or paper cups, even newspaper pots) work great as long as they are clean and excess water can drain from the bottom. You can also make plantable newspaper pots with a handy form!

Pepper plants under shop lights. One cool and one warm bulb provides a broad spectrum of light.
Pepper seedlings started under lights in my basement.

Choosing Grow Lights for Seed Starting

You can start your seedlings in a sunny windowsill, but I would start them a bit closer to your last frost date and be prepared to turn them every day to keep them from bending toward the light too much. They won’t be as strong as seedlings started under lights, so if you are planning to start seeds indoors every year I recommend setting up a seed starting station with grow lights.

I have a  spot in my basement dedicated to starting seeds. A plastic shelving unit gives me room to start up to 10 flats of plants. Each shelf has a 4-foot long shop light hung from the shelf above by wires, allowing me to adjust the lights up and down. I am in the process of replacing the shop lights with full-spectrum LED grow lights that produce much stockier seedlings.

easy seed starting station
My seed starting station with LED grow lights on the top shelf and my old shop lights on the bottom.

I’ve had good results with my seed starting set up for many years and it didn’t cost a lot to set up. It is advisable to replace fluorescent bulbs every year or 2 for the best results.

Plug your lights into a timer to come on for 12 hours each day.

Seedling Heat Mats

I’ve read all kinds of home do-it-yourself setups for providing bottom heat for the germinating seeds. All I can say is, please be careful! Make sure you aren’t creating an electrical hazard.

I purchased 2 seed starting mats years ago and they are still in great shape. I’ve saved many times the purchase price by starting my own seeds with these mats, so I have no complaints.

Make sure that the soil isn’t too hot for proper germination. Most seeds germinate best in the 65-85 F range. Check out this chart for optimal temps for different seed types.

How to Plant Seeds Indoors

Now that you have all of your seed starting supplies and your area is set up, you’re ready to go!

  • Add water to the growing medium so it is damp, not soaking wet
  • Scoop growing medium into your containers, leaving room to cover seeds with more soil
  • Check the seed packets to see how deep to plant the seeds
  • Sow 2 seeds in each pot in case one doesn’t germinate
  • Water the seeds lightly and cover with clear plastic to retain moisture
  • Label your containers with the crop and planting date
  • Check each day for germination and moisture levels
  • Don’t allow the soil to dry out
  • As soon as the seeds begin to germinate, remove the plastic
  • Check more often for moisture and water when the top of the soil dries out
  • If more than one seed germinates, pinch the smaller one back
  • Use a small fan to blow on seedlings and develop stronger stems

Some seeds take longer to germinate than others. Check the seed packet for the length of germination so you’ll have an idea of what to expect. See the note at the end of this article for instructions on testing seed viability.

Tips for Growing Your Own Seedlings

Damping-off is a fungal infection that causes the little plant to topple over and die. Closer inspection will reveal a pinched looking stem just above the soil line. This disease is more common when the growing medium is kept too damp, too cool, or a non-sterile soil mix is used.

If it happens, toss them out and start over with new growing medium and freshly sterilized pots. Be sure to allow the soil surface to dry between waterings. Using a mister bottle will help prevent overwatering and mimic dew settling on the little plants.

As they grow, lightly brush your hand over the tops of the seedlings 2 or 3 times a day to help them grow stronger in anticipation of their move to the great outdoors.

Organic fertilizer is less likely to burn tender roots.
Organic fertilizer is less likely to burn tender roots.

How to Fertilize Seedlings

If you used a growing medium that contains a timed release fertilizer for seedlings, you won’t need to provide any nutrients until they are transplanted to the garden. Otherwise, use a very weak solution of kelp or fish emulsion to water them once a week or so.

Don’t overdo it! It is very possible to ‘love’ your seedlings too much and burn their tender roots with too much nitrogen. Most fertilizer containers will give instructions for use on seedlings.

Cabbage seedling just transplanted to the garden.
Cabbage seedling just transplanted to the garden.

How to Harden Off Seedlings

As the date of your average last frost approaches, you’ll want to harden off the seedlings to get them ready for life in the great outdoors. Neglecting this step could expose your baby plants to extreme temperatures and wind that can kill them.

  • Move seedlings outside on warm, mild days for a few minutes and place them in a protected spot out of direct light
  • Increase their time outside each day, as weather allows, and don’t leave them out overnight until all danger of frost has passed and they are fully acclimated
  • Check your seedlings often to prevent drying out or sunburn
  • When the overnight temperatures are warm enough, you may transplant them into the garden
Rows of cabbages in my Dad's garden.
Rows of cabbages in my Dad’s garden.

How to Transplant Seedlings in Your Garden

When the seedlings are ready to transplant to the garden, and the chance of frost has passed, make sure their new home is ready for them. Till the soil and prepare the bed.

  • Water seedlings about an hour before transplanting so they’ll have time to soak up all they need.
  • If they are root-bound gently loosen the roots so they will grow out instead of in a ball.
  • Plant at the same depth as they were in their pots. Tomatoes are one exception…they can be planted up to the newest set of leaves. Pinch off lower leaves and roots will form along the stems to get them off to a strong start.
  • If possible, cover each seedling with a row cover or shade cloth to protect them while they adjust. Don’t cover them with anything that will heat up in the sunlight. Glass and black fabric may cook them, even on an overcast day.
  • Water them well as their roots have been disturbed and won’t be able to absorb as much for a few days.

Get Hooked on Starting Seeds Indoors!

Starting your own flower and vegetable seedlings is a rewarding and fun process! Once you’ve got the hang of it, you’ll wonder why you ever bought starts from the nursery. Congratulations…you are officially addicted to gardening!

Testing Germination Rates

If your seeds are old, you may want to test their viability, or ability to germinate. Place 10 seeds on a damp paper towel and fold it over. Place the paper towel in a plastic bag and label it with the date and seed variety. Leave in a warm place and check every day.

Some seeds germinate quickly, like lettuce and cabbage. Some seeds, such as peppers, take longer to germinate. If the seeds have not germinated consistently after 2 weeks, purchase fresh seed to replace them.

Some seeds, such as parsnips, do not germinate well after just a year. Others will keep for long periods with no problem.

hot peppers - planning the best vegetable garden

Hints for Starting and Transplanting Peppers

Pepper plants like heat. You will want to wait a couple of weeks or so after your average last frost date to transplant them into the garden. Warm the soil up with black plastic or the black landscape fabric for a few days before planting peppers. Cover them if night time temps are expected to drop down below 60 F.

Do you have any tips, hints, or tricks for starting your seedlings indoors? Leave a comment!

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