Skip to content
Home » How To Start Seeds Indoors: The Ultimate Setup

How To Start Seeds Indoors: The Ultimate Setup

  • diy
How to start seeds indoors + the ultimate setup

Starting plants from seed can help you get an early jump on the gardening season and save a few bucks in the long run. 

Today, I will walk you through everything you need to assemble the perfect seed starting station, give you a tour of my own station, and give some tips to help you start plants from seed.

Tour My Seed Starting Station

This setup is actually in my greenhouse, and not inside my house or garage, but it is generally the same principle when setting things up indoors. I may have a few extra items you won’t need if starting indoors, which I’ll point out and explain why in this article.

Start With Simple Shelving (Preferably on Wheels)

Shelving doesn’t have to be fancy. Keep things simple with a rolling metal shelf with enough space for plants to grow tall. You can also mount shelves on the walls using brackets. 

I have both in my greenhouse. Brackets that hold 11″ wooden shelves (sealed with black outdoor paint), as well as a free-standing shelf in the corner that I can move outdoors when acclimating my plants to the harsh sun or elements.

DIY greenhouse with shelves across recycled windows

Additionally, I use stackable shoe boxes under my potting table as extra space to stack plants, and as protection for some of my more sensitive plants. It’s doubly protected against the cold, and against mice in my greenhouse who like to nibble on young plants. See these shoeboxes in action here via video:

Seed Starting Pots & Trays

Buy hardy seed starting pots once, wash them out with a bleach-water solution, and use them year after year. Look for sets that include a humidity dome to protect the plants and keep them moist during germination.

Most common cell packs are medium-sized 6-cell seedling trays, smaller 12-cell seed trays, or individual pots. I like to have a mix of each for the various types of seeds. Some plants I sow with just a few seeds to smaller cell trays (like eggplant, tomatoes, and larger plants), others prefer being in bunches together (like spinach) and are sown in individual containers, larger pots, or full trays. 

You don’t need to buy fancy seed starting trays if you are on a budget. 

Budget-friendly DIY options include: 

  • Simple plastic cups from the grocery store with drainage holes poked in the bottom
  • Newspaper pots or toilet paper rolls formed into pots
  • Egg cartons made from recycled material (the paper version only)
  • Reuse washed yogurt cups
  • Gallon juice container or milk carton (large plastic ones) (great for winter sowing!)
  • Reuse bleached pots from a local garden center

In lieu of using pots, you can create soil blocks using a soil block maker. Blocks allow for better air flow which makes for healthy seedlings.

Also, buy trays that are at least a couple of inches deep and have no drainage holds. Place your seed starting pots inside the trays, and fill the TRAY with an inch or so of water when watering the seedlings. This is bottom watering rather than pouring water on top of the plant. It keeps water from splashing onto your seedling and causing disease, plus it ensures it is deeply saturated down to the roots. 

When I know I will be out of town for a week, I can fill the trays with enough water to last the entire week!

Seed Starting Medium

You’ll want a seed-starting mix uniquely formulated as a germination medium. Don’t use regular potting mix or garden soil for starting seeds. Often these will have fertilizer germinating seeds don’t need at this stage, as well as soil pathogens that can cause diseases that prevent your seeds from germinating. 

Specialized seed starting soil mix contains perlite, vermiculite, and peat moss. Or if you prefer something peat-free, go for a coconut coir mix. 

Clip-on Fans

Fans are probably one of the most important items in my greenhouse, but they are also very helpful for indoor seed starting.

Clamp a small fan onto each shelf to keep the air circulating around your seedlings. It mimics the breeze in nature to help develop sturdier stems and helps prevent fungus and mold growth on the soil surface (called damping off).

Clip on fan

Grow Lights

If you are starting seeds indoors in a house or garage, you should definitely use a grow light. Even if you have a sunny window in a room that gets a lot of natural light, it might not be enough light. Most outdoor garden plants need 6 hours of light per day.

Without adequate light, seedlings grow tall and leggy seeking out the sun, and this makes for weak stems and other problems down the line. You’ll want a supplemental light source.

But are grow lights different than regular lights? Yes! They are designed specifically for plant growth and give off more of the red and blue light spectrum than regular bulbs or even fluorescent bulbs. So, while you could still use standard fluorescent lights, it will not be as beneficial or mimic the benefits of the sun. For sun-loving plants like tomatoes, peppers, cucumbers, eggplant, melons, and more, this will dwarf their growth and health.

Seed starting trays with grow lights and heating mats

Seedling Heat Mats & Greenhouse Heater (optional)

If you are in a temperature-controlled environment, you may not need heating mats or a heater. The only warmth in my greenhouse is a small greenhouse heater and heating mats. 

If it is too cold, seeds won’t germinate. Warm soil not only helps the seeds germinate, and germinate faster, but it is better for the plant. Cool, wet soil can cause a fungal disease called damping off that kills your baby seedlings or causes seeds not to germinate. Warm things up, and you’ll have a much better start. 

The benefit of heating mats is localized heating rather than changing the entire room temperature. It saves the energy bill, while still boosting the soil temperature.

Greenhouse heater

For those of you who are starting in an unheated greenhouse, the combination of heating mats and a plug-in greenhouse heater is a lifesaver! While you could get by without it, you’ll have so much more flexibility to get a head start with it. A greenhouse heater with a temperature-controlled plug unit will heat automatically at whatever temperature you set it to start or blow a fan at the temperature you set. 

NOTE: These small greenhouse heaters may take the edge off freezing temperatures, but it will still get very cold, and you should plan for heavy freezes accordingly. I turn on my heating mats and the greenhouse heater during an expected freeze. 

Plug Protectors & Plug Timers (optional)

Plug protectors keep water from splashing on plug ends, which often happens while watering plants in a greenhouse. And plug timers are a great way to automatically control when the fans turn on (mine turn on during the day only), and when the heating mats turn on (mine turn on evenings when the temps drop, and turn off late morning when the sun hits the greenhouse). 

Tips On How To Start Seeds Indoors

Now that you have your ideal setup, and followed some of the instructions from above, you’re ready! 

Here are a few extra tips to help get you started, plus common seed starting mistakes to avoid.

Let The Seed Starting Soil Absorb Water BEFORE It Goes Into Pots

Before sowing seeds, stir the seed starting mix in a large bucket with water until it is moist and fluffy. Give it time to absorb the water, and make sure there are no dry spots. THEN scoop it into your starter pots. A common seed-starting mistake is planting the seed in dry soil and then top watering it. Often these mixes have dry spots that don’t want to absorb water, so you must help it along. 

How Deep Should I Plant Them?

A general rule of thumb is to plant your seeds 2-3 times deep as they are wide. But check the back of your seed packet, because some seeds need light to germinate and prefer almost no soil covering them.

Getting Timing Right: When To Start Seeds Indoors

The average recommended time is anywhere from 6-8 weeks before your last frost date, but it can also depend on a few other factors. The primary mistake you want to avoid is starting when it is just too cold for your seeds to germinate properly (if you are using an unheated or underheated greenhouse/garage), the plant becomes overgrown in the pots before you can plant them outside. Overly mature plants that have long outgrown their pots will struggle more when planted in the garden and may be more prone to disease. 

Check the seed packet instructions for recommendations on each plant, because seed germination may take longer for some plant types than others.

Also, ensure you are starting seeds in the right season. Warm-weather crops like tomatoes, corn, eggplant, cucumber, marigold, etc., are started in spring to grow in summer. Cool-season crops like lettuce, peas, cabbage, violets, etc., grow best in fall or early spring.

Pot Up Plants As They Outgrow Their Containers

“Potting up” simply means moving the seedling from the smaller pot to a larger one as it grows. It will stay dwarfed in size if you don’t transplant them.

If I have the budget for it, I like to pot them up into peat pots or cow pots (similar to peat pots, but without the peat content…it uses dried manure instead). These can go directly into the ground without having to disturb the roots. 

TIP: This is usually the time when you can use a water-soluble fertilizer to feed your young seedlings. Don’t do it until they at least have their first true leaves (after the initial sprout / baby leaves).

Start seeds indoors: Potted seedlings in a greenhouse

Don’t Neglect Hardening Plants Off

Plants started indoors aren’t used to outdoor elements, and they must gradually acclimate. Harsh sun, wind, dramatic temperatures…your seedlings have been coddled to this point.

It may take 1-2 weeks, depending on conditions. Take them outdoors and place them under indirect sunlight for two hours on the first day, then lengthen the amount of time they spend outdoors each day. Expose them to more sun each day, but keep the soil moist.

The Benefits of Starting Seeds Indoors

By now, you are wondering if the cost of creating a seed starting setup is worth it. 

After purchasing shelves, fans, lights, heating mats, trays, and seed growing medium, you might think it was easier just to buy the young plant instead. 

However, there are a lot of great reasons to start from seed, some of these benefits include the following reasons below:

Starting seeds - seed packets and saved seeds

It Can Cuts Costs (In The Long Run)

Who are we kidding, gardening can be expensive. Cut down on the cost by saving seeds year after year and starting your own seedlings. Of course, you have to be really intentional about saving seeds. But even if you still find yourself buying seeds, they are considerably less expensive than buying starts.

Yes, you buy seed-starting equipment…but you only need to buy it once (with the exception of seed-starting soil). After that, you’ll start spending less sowing seeds than buying starts.

You Can Grow Unique Varieties

You’ll have access to a wider variety of plant options compared to buying pre-grown seedlings from nurseries and garden centers. One year I grew 10 varieties of broccoli…I didn’t even know there were so many varieties out there! Just when you thought you hated a specific vegetable, there might just be a variety out there that will convert even the toughest critic. 

Broccoli plants under a chicken wire cover

Your vegetable garden is going to boast amazing and healthy plants!