You can save a lot of money by growing your vegetables and flowers from seed versus purchasing mature plants. But if you’re going to successfully grow your plants from seed, you need to give them the best shot at reaching adulthood (and ultimately yielding you tasty veggies or attractive blossoms). You can give them a leg up with seed starting mix. Unlike soil, seed starting mix offers the right balance of nutrients, moisture retention, access to oxygen, and disease protection plants need to survive from seed to maturity.
What Is Seed Starting Mix?
Seed starting mix is a soilless material that provides those just right conditions that seeds need to germinate. Seeds are typically planted in seed starting mix indoors in seedling trays or small pots. Once seedlings develop two sets of true leaves, they are ready to graduate to your garden. Seed starting soil is typically made of three ingredients:
Peat moss: Made up of decomposed sphagnum moss and other plant material found in boggy conditions, peat moss retains moisture well and offers a disease-free environment that’s light enough to allow for roots to grow through it easily.
Perlite: This volcanic glass that resembles styrofoam improves soil aeration, allowing oxygen to easily reach young plant’s roots.
Vermiculite: This mineral-rich material retains moisture well so young roots are less likely to dry out, while also aerating the soil.
Is Seed Starting Mix Necessary?
You don’t need to use seed starting mix. Seeds certainly have the ability to germinate and grow outdoors in regular soil. In some cases, it may not make sense to use seed starting mix, such as when you’re seeding a large area for wildflowers. That said, it makes sense when you’re growing vegetables as it significantly improves the seeds’ chances for germination and creates a disease-free environment that gives fragile seedlings the best odds of maturing to adulthood.
Benefits of Using Seed Starting Soil
Starting soil offers several advantages over common soil when it comes to growing plants from seed:
It’s disease free: Since starting soil is a sterile environment, the seedlings are safe from diseases and insects that can plague soil.
Optimal consistency: Starter soil is fine and loose, allowing the delicate roots of seedlings to grow through it more easily than heavier soil.
Moisture retention and aeration: Starting soil retains moisture well, while still being loose enough to allow for airflow, creating the perfect environment for seed germination and growth.
Low nutrient content: While this may sound like a bad thing, it’s really not. Seeds have enough nutrients stored inside them to germinate and grow, so they don’t need to draw a lot of nutrients from the surrounding soil. And since starter soil has a low nutrient content, the seedling’s roots are encouraged to grow outward to seek additional nutrients, which helps them develop a strong root system.
What Is the Difference Between Seed Starting Soil and Potting Soil?
Seed starting soil isn’t soil at all. Instead, it’s made up of fine materials like vermiculite and peat moss that are low in nutrients. Potting soil, in comparison, has a heavier feel and includes soil, compost, and a much higher concentration of nutrients. While seed starting soil’s make-up encourages seed germination and seedling growth, potting soil is designed to provide all the nutrients potted plants need.
How to Make Your Own Seed Starting Mix
You can purchase premixed seed starting mix or make your own by purchasing a few ingredients. Creating your own mix is simple. Mix together one part peat moss or coco coir, one part vermiculite and one part perlite, all of which you can find at most big box home improvement stores, in a large tub using a shovel. Though optional, you can also add worm castings (aka worm poop) to the mix to give it an extra kick. You’ll find worm castings available through online gardening sites or at a local garden center. Add water until the starting soil is saturated enough that you can form it into a ball. Then it’s ready to have seeds planted into it.
How to Make Potting Mix for Potting Up
While potting soil has a few of the same ingredients as starting mix, there are some key differences. To make a potting mix, combine three parts peat moss or coco coir, two parts compost or worm castings, and one part perlite.
Where to Buy Seed Starting Mix
If you want to avoid buying the individual ingredients, you can purchase premade seed starting mix. It’s available at local garden centers and in the gardening department of most major home improvement stores.
What is the best soil for starting seeds?
True to its name, seed starting mix is the best option for starting seeds. The mix of perlite, vermiculite, and sphagnum peat moss create a sterile, disease-free environment that provides the optimal amount of air flow and moisture retention to promote seed germination and growth.
Do I need a sterile seedling mix?
Yes, and here’s why: A sterile seed mix isn’t susceptible to the diseases and pests found in non-sterile mixes. With a sterile seed mix, you won’t have to worry about your seeds succumbing to fungus that can lead to damping off, a disease that causes young seedlings to die via rotting stems at the soil line. A sterile seedling mix also won’t contain pests that can destroy seedlings, such as fungus gnats, spider mites, leaf miners, and aphids.
Is perlite or vermiculite better for seed starting?
Both should be included. Use a combination of perlite and vermiculite in your seed starter mix. Perlite’s porous structure helps to aerate the soil, so oxygen can more easily reach the tender roots of young seedlings. Vermiculite has excellent water retention qualities, providing the moisture seedlings require to grow.
Does seed starting mix expire?
While some seed starting mixes have use-by dates stamped on them, that doesn’t necessarily mean you can’t use a seed starting mix that’s passed that date. If you keep seed starting mix in a cool, dry place, it will stay usable for a long time, though there might be some depletion in its nutrient content. If the starter mix has been sitting on the shelf for a while, add a small amount of compost to rejuvenate it.
Can I reuse seed starting mix?
You can reuse seed starting mix, but it’s usually not worth the effort. Since starting mix can pick up pathogens when you use it, you’ll need to heat it to 200 degrees for about 30 minutes in the oven, pour boiling water over it, or microwave it to sterilize it. If putting dirt in the same places where you cook food makes you cringe, then dump your old starting mix in the compost bin and make or buy some fresh mix.
How much does it cost to make your own seed starting mix?
You stand to save a lot of money by making your own seed starting mix versus buying a premade mix. You’ll spend around $10 to make about a cubic foot of seed starter mix. You’ll pay twice that amount for a commercially made seed starter mix (though you might pay more at first since purchasing larger bags of individual ingredients will initially cost more).
What can I do with old potting soil?
There are a number of things you can do with old potting soil. Adding potting soil to your compost bin helps break down compost. You can also use it to help build up soil in existing garden beds or when creating new raised garden beds.