A Beginner’s Guide to Indoor Seed Starting: Seed Starting Set-Up — Backyard Harvest Project (2024)

As another season of Covid Uncertainty rolls around, I see the gardening momentum started in 2020 is continuing into the winter of 2021. Gardening Instagram is filled with people starting seeds and sharing portraits of new little seedlings. When I started gardening, I found the whole process of seed starting daunting. The science, the equipment, the timing, the management. This guide is meant to help you get started off on the right foot.

Do I Need to Start Seeds Indoors?

Maybe. Zone 4 or 3 gardener? Likely. The reason we start seeds indoors in a short-season climate is to ensure our plants produce before the growing season ends. Most gardeners can tell you the heartache of a giant sunflower head that is just about to bloom as the snow starts to fall on it. However, there are pros and cons to indoor seed starting that you should be aware of before you get started.


  • Short season gardeners can grow long season plants.

  • Cost savings on plants - bedding plants are significantly more expensive than a package of seeds (see note about seed start investment below).

  • Allows you to grow a much wider variety of plants than what you might find at your local nursery.

  • Allows organic gardeners complete control of seed types and soil inputs.

  • Scratches that mid-winter gardening itch.


This is where you can press the eject button on seed starting. New gardeners or gardeners with less time to invest can start lots of seeds outdoors (called direct sowing), and fill in any long season plants by purchasing from a greenhouse or local gardener (who got overzealous and started way too many seeds). If you are ready to delve into the world of indoor seed starting…read on.

Seed Starting Set Up for the Backyard Gardener

The options for your seed starting set up are endless. For me, I had to take the time to differentiate between a professional setup (for greenhouses, market gardeners, and other income-generating growers), and a set up for an enthusiastic hobbyist like myself. Below is my opinion on what you need (and can skip) to get started.

Basic “Cheap and Cheerful” Set-Up

This setup is ideal if you are new to seed starting, and want to dip your toes in the water. With this set up you can start a few basic veggies 4-6 weeks before planting outside and purchase some of the longer growing plants (like tomatoes, peppers, and woody herbs). You’ll be able to start 216 seeds with this setup, more if you continue to start seeds once your first batch has moved outside. If you purchase a used shelf or already have one on hand, you can create this set up for under $100.

  • 1 x shelf unit with at least 3 shelves that are at least 10” x 20” (the size of a basic seed starting tray)

  • 3 x seeding starting trays (with no holes) with a dome lid - standard size is 10” x 20”

  • 3 x 72 cell seed starting tray (I like the perforated type that also you to separate the cells in groups of 6)

  • 1 x bag of soilless seed starting mix ( I use Pro-Mix organic seed starting mix)

  • 3 x Grow Light Bulbs (I use Sunblaster 26W 6000k fluorescent bulb) with a clip-on lamp - paired with a sunny window (this will not be enough light in a dark room)

  • 1 x water spray bottle

Full disclosure - I have started tomatoes and peppers using this setup - but it’s not ideal. By the time my plants could go outside they were leggy and weak (there just wasn’t enough light). It made them more vulnerable to pests and climate damage.

Upgraded Home Gardener Seed Starting Set-Up

So you are liking gardening, and you want to start growing more veggies or cut flowers from seed. You’d like to start some seeds that need to grow indoors for 6-12 weeks. Here’s how you upgrade your seed starting set up.

  • 1 x shelf unit with at least 4 shelves that are at least 18”x48” (this will allow you to store 4 trays per shelf, with a slight overhang). Wire shelves are ideal so you can hang lights from them. I purchased this shelf that has shelves that are 24” x 48”.

  • up to 16 x Seeding starting trays (with no holes) with a dome lid - standard size is 10” x 20”

  • up to 16 x 72 cell seed starting tray (I like the perforated type that also you to separate the cells in groups of 6)

  • up to 8 x 48” Grow Lights. See below for a discussion on grow lights - there are a few options for you

  • A plug-in timer for your lights

  • Soilless seed starting mix (I use Pro-Mix organic seed starting mix)

  • Vermiculite

  • Heat mats (can do a large 20” x 48”, or just get one or two smaller 10”x20” mats and use them for seeds that really demand heat to germinate)

  • 1 x water spray bottle

  • 1 x watering can

  • 1 x small fan

I’m cheap when it comes to gardening, so I am building my grow light set-up shelf by shelf. Each shelf can handle four seed trays (with dome and insert), one large heat mat (20 x 48”), and two 48” grow lights. Your investment is going to vary widely based on the grow lights you purchase. For 2021 - I’ll have 2 shelves ready to go, with an eye on expanding by one shelf next year.

Starting Medium

I have started seeds in a random potting mix mixed with random compost and had varying levels of success. This year, I am using a sterile soilless mix.

We want to start seeds in a sterile medium so we don’t have fungus & diseases messing with our seed growth. Dampening off is a common fungal disease the will kill your little seeds before they really even get started. In addition to it being sterile, it’s important that your seed starting medium is light and fluffy so those new little roots can grow.

I use Pro-Mix organic seed starting mix. It promises me it has “organic fertilizer” that will gradually feed my plant for “up to three months”. Given this a marketing claim, I really have to way to know if it’s true, and my seedlings will definitely be in soil before that three-month mark is up.

Is there a cheaper option? I’m sure there is, but I like the ease of just going to my garden store and buying a bag of the stuff. You’ll find recipes all over the Internet that combine seed starting mix with compost and worm casting (worm poop, super high nutrient good-stuff). The scientific jury is out on this method, so I prefer to keep it simple and stick with the commercial product.

Containers & Trays

You can start seeds in so many different containers and trays, but to keep things simple, I like to start all of my seeds using 72 cell seed starting inserts in 10”x 20” trays with a dome. If you are gentle with this equipment, it will last you for several years. I do like inserts that are perforated. I’ll explain why when we get into the process of seed starting.

When it’s time to pot up (or move seedlings to a bigger container) then things get a bit more eclectic for me. I use 4” pots, yogurt containers, red solo cups and even large peanut butter tubs. Ideally, your container will have a straight or flared lid (if you use a container that gets smaller at the top, it’s harder to remove the seedling when it’s time to transplant). It’s also CRITICAL that you create drainage holes in your container. You can purchase 3.5” round pots - you’ll fit 18 per tray. Just keep in mind some bigger plants (like tomatoes) will need bigger containers again.

Skip the egg cartons for seed starting. The cells are so small, they dry out quickly. I find they are more hassle than they are worth. I also didn’t like using biodegradable pots. I had issues with mold, and they aren’t re-usable.

Additional Supplies

In addition to lights, a starting medium, and containers, there are a few other items you might need.


Vermiculite is dry compressed flakes of a silicate mineral. Its main purpose in seed starting is to hold moisture. You sprinkle it on top of your seed starting tray - it’s ideal for seeds that say ‘keep the soil moist until germination’, but you can use it on all of your seed starts. Vermiculite is optional, if you are trying to keep costs down, you can skip it.

Heat Mats

Heat mats come in 10x20 in size, which fits one tray, or 20 x 48 , which can fit 4 trays. The key to seed starting is heat and moisture. Heat mats makes make things easier, especially if you are starting seeds in a place with a cooler ambient temperature (like your basem*nt). Heat mats are also optional - they will just speed up and increase your seed germination.

Spray Bottle + Watering Can

A spray bottle is not optional. They are inexpensive, and it’s how you ‘water’ your tiny seedlings. The flow from a proper watering can will dislodge their tiny little roots from the seed starting medium. You’ll use the spray bottle at first, and then a watering can with multiple holds on the spout as your seedlings get larger.


Running a fan on your seedlings will help them get tougher for their eventual move into the great outdoors. If you don’t have a fan, you can just ‘tickle’ your seedlings. So this item is also optional.


Grow lights need to be on for about 14-18 hours a day. A simple light timer will ensure your seedlings are getting the correct amount of light. This is also optional, but I highly recommend it (mostly because I’m a bit lazy, and I love to automate things).

A large plastic storage bin with a lid

I dump all of my seed starting mix into a bin so I can ‘pre-moisten’ the mix. You could just do this in the bag, but I like adding several bags of soil starting mix at once, so I find the container handy.

A grow tent

I really don’t know much about the little grow tents you see on the market. I can see how they would help increase heat and moisture, but I have never used one for basic home gardening.

Phew. Now that you understand all of the supplies you might need, it’s time to talk about the method & timing for seed starting. Stay tuned for part two of this blog post.

A Beginner’s Guide to Indoor Seed Starting: Seed Starting Set-Up — Backyard Harvest Project (2024)


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