Starting seeds indoors doesn’t require a greenhouse either! All you need is a sunny window. Read along for a full guide and the best tips and tricks on how to start seeds indoors.

The Benefits of Starting Seeds Indoors

Other than the health benefits of gardening, starting seeds indoors has a ton of benefits.

Longer Growing Season

Starting seeds indoors gives those tiny baby plants a healthy opportunity to thrive before the outdoor growing season in your area. For places like where I live, we have a shorter growing season due to a colder climate. This means by starting seeds indoors, it ensures your plants are ready to go in the ground as soon as the weather is favorable, maximizing your growing time and increasing your produce or flowers.

Control Over Environment

When plants are grown indoors, you can control the temperature, light and humidity of the space. This gives your seeds the best chance to germinate and grow strong without the threats of pests, unpredictable weather or whatever Mother Nature throws at you.

Stronger, Healthier Plants

By having control over the environment, you’re also increasing your chances to grow strong, healthy seedlings that are more likely to thrive once transplanted outdoors. Plant starts that have had consistent warmth and sunshine are more likely to be stronger and larger than plants that have been started in an inconsistent outdoor environment.

Succession Planting

Succession planting is when you start stagger planting by planting out some starts earlier than others to maximize the harvest and minimize threats. When seed starting, you could plant some tomato seeds, for example, in the beginning and some at the end of May. That way, instead of putting all your tomato plants in the ground all at once, you stagger them. Staggering aka succession planting can prevent you from having way too much produce at one time. It also helps if some of your first round of plants get taken out by late frost.

Lower Cost

Growing plants from seed is much cheaper than buying fully grown plants or even seedlings from the garden center. Starting your own seeds saves money and you can access a wider variety of plants than you could find at most nurseries. For example, heirloom varieties are often a bit more expensive and by planting seeds, you can get those plants for a much cheaper rate.

Where to Place Seed Starts Indoors

Maybe you have a small house and not much room to dedicate to growing. That’s ok! (In that case, you also may be interested in the best houseplants for small spaces.) You don’t need to dedicate a full room in your home or fancy equipment when starting seeds indoors either. A sunny windowsill can provide plenty of space!

Any of the following spaces will be helpful starting seeds indoors, just remember to avoid cold, drafty areas. You don’t want to place your delicate seed starts near uninsulated windows or in a place where there may be wild temperature fluctuations. Tender seedlings like consistent, warm areas.

Ideas for Where to Place Seed Starts Indoors

A Sunny, Warm Window

Most seeds need 6-8 hours of sunlight to germinate. A south-facing window tends to be best because it will provide the most sunlight. Be sure to continuously check on your seeds to ensure they aren’t burning. We don’t want to scald the tender seedlings either! Lastly, make sure to turn your seed trays. You don’t want some seedlings hogging all the light or becoming “leggy.”

Under Grow Lights

If you don’t have a spot in your home with 6-8 hours of sunlight, you may want to invest in grow lights. Grow lights provide consistent and reliable light to your seedlings. Keep the lights on for 12-16 hours per day to mimics the outdoors at this time of year. Grow lights are nice because they allow you to put the seeds almost anywhere in your home including basements and dark corners.

Don’t forget warmth!

Seeds like warmth too, so don’t forget that element when setting up your indoor seed growing area. If your house tends to be cold or you are keeping your starts in the basement or on the floor, you may want to consider buying a heat mat. A heat mat will provide the seeds with continuous heat regardless of fluctuating temperatures indoors or out!

How to Start Seeds Indoors

Read Your Seed Packets!

I cannot stress this point enough! Read the back of your seed packets! The back of the packet will tell you everything you usually need to know about the seeds, including whether or not your seeds like to be transplanted. Transplanting is when you grow a plant from seed in a small container or pot, then transplant them into the ground later. Not all plants like to be transplanted. In fact, some won’t make it if you transplant them. Corn and root vegetables, for example, don’t like to be transplanted.

The back of the seed packet will often also indicate when you should plant your seeds for your area. If the packet doesn’t tell you this, a quick Google search will!

Prepare Your Containers or Soil Blocks

If you are on a strict budget or just starting out, you can start seeds in upcycled yogurt containers or even toilet paper rolls. Just make sure that your container has proper drainage. For most seeds, containers that are 2-3 inches deep are fine. You can also always transplant to a larger container before putting your plants into the ground.

Sometimes garden centers will also give away old pots. Just be sure to sanitize reused pots, so you don’t spread any possible diseases.

If you want to level up, seed trays are the way to go. Seed trays, in my experience, make seedlings much easier to move and often come with a cover. This is helpful when you have seeds that prefer a lot of humidity and require misting or just need to stay damp.

Soil Blocking

If you want to level up and be more environmentally conscious, try soil blocking! Soil blocking is a way to start seeds that is completely plastic-free. With soil blocking, you use a handheld soil blocker to compact soil into a block that the seed is then directly planted into. Soil blocking also may be better for the plant because the roots aren’t bound up in a pot. This means the roots get more oxygen which helps growth. I’m trying soil blocking this year and so far, so good!

Shop the post:

Prepare Your Soil

Potting soil for seeds is different than your everyday garden soil because regular garden soil can be too heavy for seedlings to poke through. Seed starting mixes usually contain materials like perlite, vermiculite and coconut coir to help make the soil light and help the seeds retain moisture.

Plant the Seeds!

First, fill the containers with the seed starting mix. You’ll want to leave about an inch from the top of the container, so the soil doesn’t spill over when watering. Then plant the seeds in the soil according to instructions on the seed packet. Some seeds need to be planted close to the surface, where as others require a depth 2-3 times the seed size. Lastly, gently press down the soil to ensure the seed is in contact with the soil.

Label

It’s funny how many times think “I’m going to remember what this plant is” and I never do. Haha! Don’t be like me, label your seedlings! This is especially important when you have different varieties of the same plant and they all look the same. I like this indelible garden marker and these labels, but you can also just use a Sharpie and some tape.

Water Gently!

You’ve put so much time and effort into planting, so be sure to water gently! You don’t want to have all your hard work float away. Use a watering can with a fine sprayer, or if your planting seeds like lettuce that can easily get washed away, place your seedlings in a shallow tray of water to soak up water from the bottom.

Thin seedlings

Some seedlings, depending on how they like to be planted, also need to be thinned. This means plucking out the smaller, weaker seedlings to prevent over-crowding. Vegetables like lettuces, radishes, kale and carrots all need to be thinned once they produce their first “true leaves.” True leaves are the second set of leaves to grow on a seedling.

Harden Off

Before popping your seedlings into the ground outside, you’ll need to “harden” them off by acclimating them to outdoor conditions a little bit at a time. Make sure this is after your areas last frost date.

First place them in a sheltered, shady area for a few hours a day. Then after a few days, gradually increase their sunlight until your seedlings have fully hardened off after about 10 days. Be sure to keep an eye on the weather too. Even though your plants are going through a hardening off period, this doesn’t mean that they need to sit through a freak frost or torrential downpours. You can still bring them inside for short periods if the weather isn’t cooperating.

Transplant

After your plants have been hardened off, transplant them into your garden, or into larger pots if you are doing a container garden. Either way, make sure the soil is loose and that you water the plant in well after planting.

Tips and Tricks for Starting Seeds Indoors

Don’t reuse old soil

It’s tempting to reuse soil from last year’s containers, but there’s a few problems with that. First, the soil could have diseases in it that could kill or inhibit the growth of your new plants. Additionally, the soil is depleted of nutrients from its previous use. I like to add old soil to my compost pile.

Clean and sanitize your tools and containers

We all want to be lazy and skip this, but always clean and sanitize your tools and containers. Your tools and old containers can harbor diseases or mold– neither of which you want to introduce into your garden. To clean, I like to rinse off my tools and containers with a hose to get off any initial debris. Then, I’ll go in with a brush to get off anything that the hose couldn’t take off. Next, I dunk in a gallon of water with 1/8 of a teaspoon of bleach. This small amount of bleach is enough to kill anything lingering. Then, let air dry and your tools or containers are sanitized.

Don’t fertilize seedlings

It’s understandable– you want your seedlings to do their best and adding fertilizer makes sense, right? Wrong unfortunately. Seedlings are delicate and easily be burned by fertilizer, so wait on fertilizer until you’ve transplanted the plants into their final spot.

Phew! I know starting seeds indoors seems like a lot of work, but the gardening is such a fulfilling hobby. If you have any more tips for starting seeds inside, be sure to leave them in the comments!