Learn to start seeds indoors with this DIY system! Get your seedlings off to a strong start with these 11 essential supplies.

Starting your own seeds indoors is incredibly rewarding, but those pre-made seed starting kits can put a serious dent in your gardening budget. The good news? You can create a DIY seed starting system that’s just as effective (if not more so!) for a fraction of the cost.

In this guide, I’ll walk you through the 11 essential supplies you need to get your seedlings off to a strong start without breaking the bank. I use this set-up every year, every season, to create a gorgeous cut flower garden filled with beautiful blooms. So let’s embrace the power of DIY and make this one ourselves!

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A vibrant garden full of colorful flowers in bloom. The foreground boasts an assortment, including pink dahlias, yellow zinnias, and orange blooms. In the background, partially obscured by trees and plants, is a traditional greenhouse with a peaked roof—a perfect cut flower garden.

11 Must-Have Indoor Seed Starting Supplies

Let’s get your DIY seed starting system up and running! Below are the 11 essential supplies you’ll need to gather. I’ll share details about my own setup later, but first, let’s cover the basics…

  • Seeds: This might seem obvious, but high-quality seeds are the foundation of your success! Choose varieties suited to your climate and gardening goals. (Link to reputable seed sources like the ones you mentioned)
  • Vermiculite: While not strictly necessary, vermiculite is a fantastic seed-covering medium. It’s lightweight, helps retain moisture, and allows seedlings to emerge easily.
  • Seed Starting Mix: Unlike regular potting mix, seed starting mix is finer and lighter, providing the ideal texture for delicate seedlings.
  • Seed Trays: These come in various sizes and configurations. Choose seed trays that fit your space and the number of seedlings you plan to start. I usually go with the 72 or (2) 36 cells.
  • Bottom or Drainage Trays: Essential for catching excess water and preventing soggy roots. Look for drainage trays that fit snugly beneath your seed trays.
  • Clear Dome Lids: Clear dome lids create a mini-greenhouse effect, maintaining humidity and warmth for optimal germination.
  • Grow Lights: Crucial for providing adequate light, especially in areas with limited sunlight. LED grow lights are energy-efficient and provide the right spectrum for seedlings.
  • Programmable Timer: Timers help your lighting go on and off daily with a low-maintenance, set-and-forget approach.
  • Table or Shelf System for Seedlings: A sturdy surface to hold your trays and lights. You can DIY a system using wire shelves, as I did, or repurpose existing furniture.
  • Heat Mat: Heat mats provide gentle bottom heat, which can significantly speed up germination. Not all seeds need additional heat, so read the seed packets for information.
  • Plant Labels: Don’t forget to label your trays! You’ll be surprised how quickly you forget what you planted where.
  • Oscillating Fan: Oscillating fan improves air circulation, which helps prevent damping-off (a fungal disease that can kill seedlings).

Where to Buy Seeds

It’s almost time to start planting certain flower varieties, so I already have my seeds. If you don’t have yours yet, check with your local nursery, big box store, or reputable online retailers like Floret Flowers, Johnny’s Selected Seeds, and Renee’s Garden.

DIY seed starting system before Hardening Off Plants After Starting Seeds Indoors - close up of indoor seed starting equipment with seedlings under grow lights

My Indoor DIY Seed Starting System

In my previous home, I started seeds in my basement. Now, I use my sunroom, which is brighter but still requires grow lights for optimal growth. The key is to have adjustable lights that you can raise as your seedlings grow.

Here’s how I created my DIY seed-starting shelf system:

  • Grow Lights: I used a combination of 2-foot and 4-foot LED grow lights, piecing them together as needed.
  • Why DIY? Pre-made systems were too expensive and lacked the space I needed for my 21 seed trays.
  • Choosing the Shelves: We opted for tiered wire chef shelves. They’re affordable, adjustable, sturdy, and can be repurposed for other uses after the seed-starting season.

How to Create a Seed-Starting Shelf System

After much deliberation, we ultimately decided on these tiered wired chef shelves. They are perfect for starting several seed trays. It’s easy to hang grow lights on them. The shelves are adjustable. Plus we can use them for more than just growing seeds. So this was a no-brainer. To accommodate roughly (21) 10″x 20″ seed trays, we bought two sets of shelves.

Tips for Choosing DIY Seed Starting Supplies

Do You Need to Use Grow Lights With Your DIY Seed Starting System?

100%!!! When starting seeds indoors, it is essential to use grow lights so you grow stronger, healthier seedlings. To grow well, they’ll need 14-16 hours of light. They just won’t get that during the depths of winter so I strongly recommend investing in lights you’ll use year after year.

You’ll also want the ability to adjust the lights as they need to be within 4 inches of your seedlings to keep them from getting leggy while they grow.

Using Complete Seed-Starting Trays

I have used these complete seed-starting systems and love them. They even have ones with a self-watering tray and peat pot cells. If you can find the ones with the self-watering tray reservoir, get them. It’s much easier to bottom water your seedlings this way.

I’ve even used 4″ deep biodegradable cells, clear plastic dome and irrigation trays too. The reason I purchased the 4″ deep biodegradable cells is because there are a few seeds that need deeper cells to start and grow in.

Re-Using What You Have With Your DIY Seed Starting System

If you want to reuse containers you already have too, make sure you properly clean them. Use 1 part bleach to 10 parts water and clean everything thoroughly to get rid of any leftover pest or disease issues.

Seed Starting Soil vs. Regular Potting Mix: Why It Matters

You might be tempted to just grab a bag of your usual potting soil and call it a day, but hold on! Seed starting mix is specially formulated to give those tiny seeds the best possible chance at life. Here’s why:  

  • Texture: Seed starting mix is much finer and lighter than regular potting soil. This allows delicate roots to easily navigate their way through the mix, leading to stronger, healthier seedlings.  
  • Drainage: Good drainage is essential to prevent soggy soil and “damping off,” a fungal disease that can kill seedlings. Seed starting mix is designed to drain well while still retaining enough moisture for germination.  
  • Sterility: Seed starting mix is typically sterile, meaning it’s free from weed seeds, diseases, and pests that could harm your seedlings.  
  • Nutrient Content: While seedlings don’t need a lot of nutrients initially, seed starting mix often contains a balanced blend to support early growth.

Soil quality can make or break any garden, so I can’t stress enough the importance of good quality seed starting mix.

What You Need to Know About Sowing Seeds Indoors - 11 must-have Indoor seed start supplies - sowing seeds in peat pots

Vermiculite: A Seed-Starting Superstar

Vermiculite is a mineral that expands when heated, creating lightweight, porous particles. It’s a fantastic addition to your seed-starting arsenal for these reasons:  

  • Moisture Retention: Vermiculite holds onto moisture like a sponge, ensuring your seeds stay consistently hydrated.
  • Aeration: The porous nature of vermiculite improves airflow around the seeds, promoting healthy root development.  
  • Easy Emergence: Seedlings have an easier time pushing through vermiculite than through denser soil.
  • Disease Prevention: Vermiculite can help prevent damping-off by improving drainage and reducing soil compaction.  

How to use vermiculite:

  • Seed Covering: Sprinkle a thin layer of vermiculite over your seeds after sowing.  
  • Mix it in: Add vermiculite to your seed starting mix to improve its texture and drainage.  

Some growers recommend using vermiculite to cover seeds after planting instead of soil. It’s not necessary if you don’t have it, but the seeds have an easier time growing through it. And after having done this several times, I prefer the vermiculite.

Heat Mats for Starting Seeds Indoors

These are the heat maps I use. Keep in mind that you don’t necessarily need the same number of heat mats as you do cell trays. Figure out how many heat mats you need based on the most seed packets you’ll be starting at one time. I did not do this and totally overbought heat mats. So don’t make the same mistake I did and save yourself a few dollars.

How to Start Seeds Indoors Without a Greenhouse - The Supplies

Plant Labels and Sharpie

I can’t stress enough how important it is to label EVERYTHING you plant right after sowing. You’ll never remember the name and variety later so do yourself a favor and label it when you sow. These are the plant tags I use. To write on them, I’m just using a Sharpie. Ultimately, you want to use something that won’t rub off too, so keep that in mind with whatever you decide to use.

Hardening off plants after starting seeds indoors with seed labels

DIY Seed Starting System: Troubleshooting and Tips

  • Damping Off: This fungal disease can be prevented with good air circulation, proper watering practices, and sterile seed starting mix.
  • Leggy Seedlings: This is often caused by insufficient light. Ensure your seedlings are close enough to the grow lights.
  • Hardening Off: Before transplanting seedlings outdoors, gradually acclimate them to the outdoor environment. Read my article about how to harden off seedlings here.
How to Start Seeds Indoors Without a Greenhouse

Common Questions Creating a DIY Seed Starting System

What is the cheapest way to start seeds indoors?

If you do some research online, you’ll see lots of ideas for DIY seed-starting set-ups – everything from using old egg cartons to making biodegradable newspaper seed pots that can be planted in the ground come spring.

Depending on your budget, reusing household containers and relying on natural sunlight may be your best (and least expensive) option for starting seeds indoors. But if you’re looking to start seeds indoors without having to rely on natural light, then creating a DIY seed-starting system is typically more cost-effective than buying a pre-made one.

And remember, while the seed starting supplies shared in this post are an investment, they can also be used year after year!

zinnias in the potager by the cottage

What month is best to start seeds indoors?

Many plants – flowers and vegetables – can be started indoors in winter to prepare for the spring growing season. Timing depends on your last frost date and when your seedlings need to be started. Some require 10-12 weeks before that last frost date. You’ll want to have your supplies in place and ready to go well before then. However, it’s important to pick your planting dates based on each individual plant and its growing time.

I share more about how to plan for seed starting in the next post in this series, sharing tips to get organized before starting seeds. CLICK HERE to get my FREE DOWNLOADABLE PRINTABLE that will help you get organized to sow seeds this year. Print as many pages as you want and add to your gardening journal for ease of reference during the growing season.

snapdragons and larkspur flowers in cottage garden that are deer resistant flowers
Snapdragons and Larkspur

DIY Seed Starting System Wrap-Up

Have you ever started seeds indoors before? What supplies did you use or would recommend? I would love to know more in the comments below.

Next up in the series, we’ll be chatting about how to get organized before starting seeds indoors.

For more information about making your own DIY seed starting system, please see this article from the University of Georgia Cooperative Extension.

Thanks for stopping by the blog today!

Enjoy your day! xoxo

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Home and Garden Blogger Stacy Ling cutting zinnia flowers in her cottage garden with wood picket fence in front of garden shed
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32 Comments

  1. For this newbie, there is so much to learn. 😊 You have given a great step by step on how to start. I am so looking forward to planting. Thanks for always sharing your knowledge!

  2. Stacy,
    I really appreciate all your information! Although I have a greenhouse, I’ll be starting a lot of these seeds inside so your information is so valuable to me.

  3. Thank you so much for sharing this! I have an enclosed greenhouse garden shelving unit that has the cover and lights and I need to get things started! It’s not large, but it was an estate sale find and I keep forgetting I have it. I hadn’t seen the heat mats. Brilliant. I love Floret.❤️

    1. Thank you! Yes the heat mats really help get the seeds going! I am so excited to see what you grow! Are you doing flowers and veggies? Yes, they produce amazing seeds! xo

  4. Your basement looks exactly like mine right now. I can’t wait to see them blooming in the garden this summer. Happy Saturday!

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  6. Last year in a pinch I used heating pad until I got the heat mats. Looks like I missed out on getting seeds from floret flowers. They were sold out 🙁 I’m enjoying watching your journey growing plants from seeds. It’s a miracle how this happens. Keep up the good work.

  7. It is so nice to read such a detailed description of how you start your seeds. I am going to start mine for the first time this weekend so it’s nice to have this tutorial for reference!!! Wish me luck:)

    1. That is wonderful Maria! I am so happy to hear that! What are you going to grow? I’m starting my sweet peas next week. Looking forward to watching our gardens grow together! xo

  8. Super informative post!! I just picked up some trays this morning…I can’t wait to get everything started!! You are a couple of gardening weeks ahead of me.

    1. Thank you so much! I am so excited to start growing stuff! It will be so much fun to grow our gardens together. I am sowing my sweet peas next weekend!

    1. Thank you Anne! I am so excited to branch out of my gardening comfort zone and try some new plants! Have the best weekend! xoxo

  9. Could you share the information that you have written in your spiral notebook? What are the categories? I see flowers, days to maturity…what else?
    thanks!

    1. Hi Margaret! I’m sharing a post tomorrow that will detail how I organized myself to start my seeds. Stay tuned! xo

  10. I support my family gardener’s by sharing posts like this. They are my husband, daughter and DIL. We all agree you can never have too many flowers!

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  12. To Stacy Ling: I added up the hardware items you used ,and in my area (Denver) You spent more than what a lean-to greenhouse costs. I counted 9 heating pads, 8 lights, 1 timer, 5 shelf bakers’ shelves. I’ll have to stick to the top of my refrigerator for heat; it gets some south facing light, and I have a West facing window which gets a lot of light, and I have a 6′ folding table there. I also have two grow lights with one bulb, not an 18″ one. I’ll have to do with what I have. Your stuff added up to $758.00 a lean-to is $641.00. I don’t know if a greenhouse needs lights or heat mats.

    1. Hi Susan! I totally understand the need to work within a budget. Every gardener is different having different needs, space requirements, hardiness zones, micro-climates and budgets. I’m so happy to hear you are growing stuff too! Best of luck with your garden!

  13. Will get a tray and start my indoor gardening activity. Excited to see plants blooming. This one is good, recommendations to start gardening.