DIY Organic Seed Starting Mix: A Flower Farmer’s Guide to Growing Healthy Blossoms on a Budget

As a flower farmers, we know that healthy, vibrant blooms begin with strong seedlings. While there are plenty of pre-made potting mixes available at garden centers, making your own seedling mix can be a game changer. Not only does it give you complete control over the ingredients, but it’s also a cost-effective way to ensure your flowers have the best start possible—without breaking the bank.

In this guide, I’ll share a simple recipe for a DIY organic seedling mix that works wonders for starting your flower seeds. This mix is light and fluffy, providing an ideal environment for your young plants to take root and thrive.

Why Make Your Own Seed Starting Mix?

You may be wondering, "Why bother with making my own mix when I can just buy one?" Great question! Here’s why I prefer to create my own seedling mix as a flower farmer:

1. Better Control Over Ingredients: Commercial seedling mixes often contain synthetic fertilizers and other additives that may not align with your organic growing philosophy. By mixing your own, you can ensure everything is natural and chemical-free.

2. Quantity: We grow a lot of flowers from seed and having bulk mix on hand is a huge time saver, plus, all of the ingredients have other uses in potting up, storing dahlias, etc so there is no waste, no last minute drive to the garden center for that extra seed tray you forgot you needed to start.

3. Cost-Effective: Seedling mix can get expensive, especially when you’re sowing hundreds of flower seeds. By making your own, you’ll save a lot of money over time, especially when you’re starting large batches for your farm. Making your own seed starting mix costs about $1 a quart if you do less than 50 quarts, quantities over that usually cost far less as you can maximize your savings by buying the ingredients in bulk. Pre-made organic seed starting mix will run you about $2 a quart. I'll try to remember to update with how many quarts we use for how many seedlings after this growing season.

4. 
   

The Ingredients You’ll Need

You can keep it simple or go all out with your process - going all out has the added benefit of making you feel like a medieval alchemist creating magic from dirt - which you totally are!.

To create the perfect seedling mix, you’ll need three key ingredients that are light, airy, and capable of holding moisture while draining excess water efficiently. Here's the basic formula I use for flower seedlings:

• Coco Coir (or Peat Moss): 1 part

• Perlite: 1 part

• Vermiculite: 1 part

  ***If you add 1 part worm castings you're seedlings will all get into Harvard***

• 
  

1. Coco Coir (or Peat Moss)

Coco coir is a fantastic, eco-friendly alternative to peat moss. It’s made from coconut husks and offers great moisture retention and air porosity. If you’re looking for something sustainable, coco coir is the way to go. It helps maintain consistent moisture levels in your seedling tray, which is essential for germination.

If you choose to use peat moss, it has similar moisture-retention properties but may not be as environmentally friendly due to the way it’s harvested and some feel it raises the ph of the mix, which is not always ideal.

2. Perlite

Perlite is a lightweight, volcanic mineral that improves drainage and prevents your mix from becoming compacted. Proper drainage is vital for healthy root development, and perlite helps achieve that. It keeps the mix light and airy, so your flower seedlings aren’t drowning in excess water. You’ll want to make sure that your seedling mix doesn’t retain too much moisture, as this can lead to damping-off disease or root rot.

3. Vermiculite

Vermiculite, like perlite, is another mineral that helps with aeration, but it also adds moisture-retention properties. It holds onto water in small quantities, releasing it slowly to your seedlings as they need it. Vermiculite also contains trace minerals that can aid in seedling development. It’s especially beneficial for flowers that need a consistent water supply as they grow, like cupcake zinnias - the quickest way for your fancy varieties to revert to the plain face versions you certainly did not splurge for, is to stress out the seedlings.

Step-by-Step Instructions for Mixing

Now that you have your ingredients, let’s get to the fun part: mixing!

1. Start with a clean container. I recommend using a large plastic bin or bucket, something with enough space to mix everything thoroughly without spilling over.

2. Measure equal parts of each ingredient (coco coir, perlite, and vermiculite). A standard ratio is 1:1:1, but you can adjust it depending on your specific needs. For example, if you’re growing flowers that prefer drier conditions, you can add a bit more perlite for better drainage.

3. Rehydrate Coir if it comes in a brick. Doing this part alone in the bucket before adding your other ingredients makes the work of mixing way easier.

4. Combine the ingredients in your container and stir thoroughly until everything is evenly mixed. You want the coir to be spread out evenly throughout the mix so that moisture is retained uniformly.

5. Add water. After mixing, it’s time to hydrate your seedling mix. Add just enough water so that the mix is very moist but not soaking wet. It should feel like a wet sponge—moist enough to hold its shape but not dripping.

6. Ready to Use. Now your seedling mix is ready to go! Fill your trays or containers with the mix, be sure your cells are fully filled as sometimes large air pockets can be hidden under the surface. The easiest way to do this is to firmly tap bottom of the the tray against a hard surface to force the dirt to settle and then refill any lower cells. Plant your flower seeds according to the instructions on the seed packets - some seeds need to be covered as darkness aides in germination, some need to have light so keep the uncovered, some need cold-stratification (here's how to do that).

   
   

Tips for Flower Growers

• Sterilize Your Ingredients: While the ingredients I’ve mentioned are generally sterile, if you want to be extra cautious about preventing any fungal or bacterial issues, you can sterilize the coco coir or peat moss by heating it in the oven (around 180°F for 30 minutes). This step isn’t necessary but can help minimize risks when you're working with lots of trays.

Use Worm Castings for Boosted Nutrients: If you’re looking for a nutrient boost right from the start, you can mix in worm castings.

• Keep Track of Moisture: The key to successful seedling growth is maintaining the right moisture levels. A misting bottle can help you keep the surface of the soil moist without over-wetting it but bottom watering the trays in the gold standard, especially for tiny seeds like poppies or snapdragons. Be sure to check the moisture regularly to avoid drying out the mix.

  
  

Conclusion

As a flower grower, there’s nothing more rewarding than seeing your blooms start from tiny seeds and grow into vibrant flowers. By making your own DIY organic seedling mix, you’re giving your flowers the best possible start in life. Plus, you’re saving money while reducing your environmental footprint—what’s not to love?

Whether you’re growing sunflowers, zinnia, or wildflowers, this simple, affordable mix will help your seedlings grow strong and healthy. So roll up your sleeves, gather your ingredients, and get ready for a season of flourishing flowers!

Happy growing! 🌸