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Make Your Own Seed Starting Mix

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January garden tasks - seed starting

Today, we’re diving into the fascinating world of seed starting and creating your soil mix. Sometimes, the costs of gardening can add up, particularly with items like potting soil that have seen recent price increases. If you’re feeling the pinch, making your seed starting mix is a cost-effective solution that’s easier than you might think.

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Seed Starting Mix Basics

Seed starting mix doesn’t have to be complicated. It only needs two things: either coconut coir or peat moss, and vermiculite or perlite. These simple ingredients provide the necessary structure and aeration for seedlings to thrive. Amendments are unnecessary at this stage since everything a plant needs for the first few weeks is in the seed itself.

Vermiculite vs. Perlite


Vermiculite is a natural mineral that undergoes a process called exfoliation when heated. This expansion results in a lightweight and absorbent material. Here are some key attributes:

  1. Water Retention: Vermiculite has excellent water retention properties, making it beneficial for plants that prefer consistently moist soil.
  2. Nutrient Retention: It can hold onto essential nutrients, gradually releasing them to plant roots as needed.
  3. Aeration: While it provides aeration, it is not as effective as perlite in promoting drainage.


Perlite, on the other hand, is also a mineral, but it is expanded by heating crushed volcanic rock. Here are its notable characteristics:

  1. Drainage: Perlite is renowned for its superior drainage capabilities, preventing soil compaction and facilitating aeration.
  2. Lightweight: Being lightweight, perlite contributes to a well-aerated soil structure without adding much weight.
  3. Neutral pH: Perlite is pH neutral, ensuring it won’t significantly alter the acidity or alkalinity of the soil.

Choosing Between Them:

  • If your goal is to improve water retention and nutrient availability, vermiculite may be more suitable.
  • For plants that demand well-draining soil and benefit from increased aeration, perlite is the go-to choice.

Some seed mix recipes use both.

The Basic Seed Starting Mix Recipe

  • 8 parts (pre-moistened) coco coir or peat moss
  • 1 part vermiculite… And/Or…
  • 1 part perlite

That’s it! It doesn’t have to be complicated. You can also mix it up with any mixture of coco coir and perlite that you have…it’s not an exact science. You just need a place for your seedlings to hang out for a few weeks so they can come to life and drink up whatever amount of water they need.

Potting Up Your Seedlings

Once your seedlings develop their true leaves, they’ll need a gentle dose of fertilizer, diluted to about 1/4 the regular strength. If they outgrow their initial containers, potting them up into nutrient-rich potting soil ensures they continue to thrive as they prepare for transplantation into the garden.

Soil Sterilization and Pest Control

Sterilizing your soil is crucial for preventing the introduction of pests like fungus gnats into your house, or other diseases into your garden. Methods like baking store-bought soil or solarization effectively eliminate pathogens and pests, ensuring a healthy growing environment for your plants.

Pouring boiling water over your mixture is another effective method of sterilization. Additionally, incorporating beneficial nematodes into your soil can help control pests like fungus gnats, safeguarding your seedlings as they grow.

Nutrient Enhancement and Building Healthy Soil

While seedlings have minimal nutritional needs initially, it’s essential to provide them with the necessary nutrients as they grow. After transplanting seedlings outdoors, consider adding organic fertilizers like compost or worm castings to provide a nutrient boost. You can also incorporate slow-release fertilizers or organic amendments like bone meal or blood meal to enrich the soil and promote healthy plant growth.

If you are building healthy soil over time, then you may not need all the amendments that are usually suggested. Most garden centers and big box stores are happy to sell you fertilizers but you may not need them.

make your own seed starting mix
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Conclusion and Recommendations

In conclusion, understanding soil composition and mastering the art of seed starting are essential skills for any gardener. By creating your own soil mix, sterilizing your soil, and incorporating alternative soil additives, you can ensure that your plants have the best possible start. Remember to focus on nutrient enhancement and building healthy soil over time to create a thriving garden ecosystem.

We have two suggestions as to where to purchase coconut coir:

  • The Dollar Store has a nice-sized bag for $1.25. We think that is the best price we’ve seen.
  • Amazon has a 16-quart package of Burpee Organic Coconut Coir Concentrate. It sold for $11.57 at the time of this publication. (affiliate link)

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