Are you planning to start vegetables, flowers, or other plants from seed?
Instead of buying transplants from the garden center or nursery, starting from seed is far more economical, plus it’s a fun project!
One of the most important supplies to have on hand is growing medium, but there are so many different types to choose from – which one is best?
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Perhaps you are a newbie and are still learning some gardening basics?
If you’re starting seeds for the first time, you’ll want to make sure to choose the right type of medium before you sow, to save yourself from heartache and disappointment.
Garden soil, potting soil, topsoil – if you find yourself at the garden nursery, looking at the different options and wondering which bag to buy to grow seedlings, this guide has you covered!
Choosing the right growing medium for this type of propagation can mean the difference between sweet success and sad, sad failure.
Ready to learn more? Here’s what we’ll cover:
What You’ll Learn
Can You Use Garden Soil?
Some gardeners may be tempted to save a buck by skipping seed starting medium and using topsoil from the back yard – or even a cheap bag of garden soil from the big box store.
You may be able to start seeds in this way, but there are a few considerations before you fill your seedling trays or nursery pots!
Garden soil that has not been sterilized can compromise the health of young seedlings, potentially introducing harmful viral, bacterial, or fungal pathogens, such as those that cause damping off.
If this unhappy condition occurs, you’ll notice the stems browning just above the soil line. The stems will wilt or shrivel, and the young plants will collapse and quickly die.
Sterilizing this type of medium can help, but pathogens aren’t the only issue.
Another potential problem with garden soil is the texture. Seedlings have small roots that need finely textured, loose growing medium so they can easily spread out.
If you have heavy, compact clay soil, your seedlings will not thrive in such a growing medium without some serious amending ahead of time.
And if you have to both sterilize and amend the substrate to make it work for starting seeds, why not just make life a little easier and start with a mix intended for the purpose?
Also, how sure are you that your backyard topsoil doesn’t contain weed seeds?
These will be difficult to kill to prepare the soil for use as a growing medium for propagation, since some weed seeds only die after spending seven days at temperatures of 180°F or higher.
Because of the difficulty of maintaining that temperature at home to alleviate the risk of weeds, using a readymade seedling mix is a much easier option.
Are Seed Starting Mixes Best?
While commercially available potting mixes can be used provided they are sterile, the lightweight media in soilless mixes formulated for seed starting enables tender roots and shoots to emerge easily.
It also makes transplanting easier.
I prefer to use soilless seedling mixes for this propagating seeds – but I always look for those free from peat moss, a gardening ingredient with heavy environmental baggage that is being banned in the European Union and the United Kingdom.
One of my favorites, Rosy Soil Seedling Mix, includes ingredients such as biochar, sand, compost, and worm castings.
Rather than providing a sterile option, Rosy’s Seedling Mix contains beneficial mycorrhizae to help young plants get established.
Want to give it a try? Rosy Soil Seedling Mix is available for purchase in eight-quart bags via Walmart.
And there are other great options especially designed for maturing plants as well!
If you’re low on space and prefer sterile ingredients, you can also use coconut coir as a propagation medium.
You can find coconut coir in packs of two concentrated space saving blocks from Burpee.
Concentrated Coconut Coir Blocks
You just need to add water, and each block will expand to eight quarts, ready for use.
Since coconut coir isn’t a nutrient-rich substrate, be sure to fertilize young plants regularly with a suitable food.
When to Use Specialty Mixes
By now, you’re probably thinking that growing mediums specifically formulated for propagating seedlings are the best choice.
But there are exceptions!
Are you growing something else besides annual veggies or flowers?
Depending on the species, you may need to choose a different type of substrate – one more suited to the plant’s needs.
If the mature plant has unusual substrate requirements chances are its seedling form will also need a special medium.
An extreme case that comes to mind is the Venus flytrap, which requires a substrate formulated for carnivorous plants when propagating.
While bog dwellers such as Venus flytraps and pitcher plants prefer moist, damp potting medium, there are also the plants from arid regions which will require their own type of specialty substrate.
As they need excellent drainage, succulents and cacti should be grown in very gritty mixes composed of 50 to 80 percent mineral content.
Clearly, the best ingredient ratio depends on the type of plant, so know what your species of choice needs before you get started.
Unfortunately, specialty substrates for starting seedlings are fairly hard to come by, so you may need to make your own.
Grow With a Good Foundation
The type of growing medium you choose is no doubt the foundation of a plant’s health – and now you know how to choose the right one from the very beginning!
Do you have any remaining questions about potting soil for starting seeds? Let us know in the comments section below!
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