Transform Your Garden with DIY Gardening Soil

The price for bagged germination mix and potting soil or raised bed soil can be cost prohibitive when you have a lot of seed trays to fill and a lot of raised beds to top off.

Creating your own soil blend can give you significantly more bang for your buck and even create healthier plants.

First, let’s talk about the different components of soil mixes so you can build your own from there.

Water retention and drainage

When gardening and growing any kind of plants, the ability for the soil to both drain and retain water at the same time is a strange but essential part of plant health.

If the soil drains too quickly, you have to water constantly so the plant doesn’t die from dehydration. If the soil retains too much, the plant will still die, but from asphyxiation.

Your ideal soil will drain well so the roots are not water logged, but still hold on to some water so the plant doesn’t dry out quickly. 

Your environment will play a role in just how quick or slow draining you will want your mix to be. If you live in the desert maybe you don’t want any drainage, while if you live in a rainforest like we do here in the Blue Ridge Mountains, you might want a good amount of drainage.

Additionally, consider the kind of container you are going to be growing in. A fabric grow bag will dry out a lot faster than a terracotta pot, and the smaller the container the faster it dries. 

Coconut coir and peat moss are the most common bases for soil mixes as they hold onto moisture very well. There is a lot of controversy surrounding peat moss so many people turn to coco coir as an alternative. If you are interested in learning about the environmental impact of both of them, that is a very easy Google search away. 

Perlite and vermiculite are commonly used to create drainage through adding air pockets in the soil. Perlite are those white, styrofoam looking rocks you find in almost every bagged mix. Vermiculite is the gold dust-like rock substance you may also sometimes come across. Vermiculite is also coming under scrutiny for testing positive for asbestos so that is another thing to be aware of. Small-size pumice/volcanic rock is another option that works well for drainage too.

Nutrition

Compost is not fertilizer! Say it with me now, COMPOST IS NOT FERTILIZER!!!

I have seen so many people (myself included) who misunderstood the nutritional application of compost and used it without any additional nutrition. I lost so many seedlings my first time making my own seed mix because I only added compost and nothing else.

As soon as I figured out what was wrong (in my case it was a magnesium deficiency that turned all my tomato and pepper seedlings purple and brittle) I top dressed the 4-inch pots they were in with balanced fertilizer and watered it in. Within 48 hours the purple was replaced with green and the plants were okay.

Since then, I still add compost, specifically vermicast and a sea-based one of lobster or crab shell compost, but I also add a balanced organic fertilizer too.

A nice, mild 4-4-4 (bonus points if there’s mycorrhizal fungi in the fertilizer you use) seems to do the trick and make the seedlings quite happy. One aspect of this though is that depending on the type of fertilizer you use, the pellets may expand when wet which can be problematic if that happens after the seeds are planted. I’ve seen the pellets expand and cover the seeds, preventing them from germinating properly which can easily be avoided by pre-wetting your soil blend and giving it a good mix before filling your seed trays. 

Amendments

Aside from composts and fertilizers, there are other amendments you can add to give your seedlings and plants an extra boost. One is azomite or rock dust to add extra trace minerals. There is also bio-char for carbon sequestration and creating perfect apartments so to speak for beneficial microorganisms to take up residence in your soil and improve water holding capacity and biological activity. 

Germination versus potting mix

Germination mix tends to be much more fine and lightweight so seeds do not struggle with pushing up through the soil or growing roots through it. It also tends to not have much if any added nutrition. Potting mix tends to be more coarse in texture and have some amendments/food added to it. When making your own blends, you get to choose what’s important to you and experiment. 

Freckle Twins’ garden seed starting mix

This blend is what I use to start thousands of seedlings on my farm. I’m always tweaking and experimenting and seeing what I can do differently, but this is my core recipe:

• 2 gallons of coco coir (straight or from a bagged coir potting mix*)
• 1 quart vermicast
• 1 quart compost (preferably something sea based for trace minerals)

Organic fertilizer and Azomite: Follow the instructions for potting plants on the labels, usually 2 Tbs per gallon (just for reference, 2 quarts equals half a gallon).

Add a ton of water, let sit for about 30 minutes and then mix and fill your trays.

You can also use a compost sieve and sift the mix before wetting if you want to make sure it’s not too chunky. I personally don’t bother with this, but it is up to you.

If using a coir heavy potting mix, you don’t need to worry about adding extra drainage since it will already have it. If you use just straight coir, add a quart of fine perlite or your choice of drainage material.

For making potting soil or a raised bed mix, the concepts are the same as when you make a germination mix:

• 4-5 parts coir 
• 2 parts compost
• 1 part drainage
• 1-2 parts soil conditioner (if you so desire)
• 1 part biochar (if you can find it/want to use it)
• Organic fertilizer and azomite or rock dust (follow the package directions)

So there you have it. Go forth, get dirty, make mistakes, grow some plants, and take notes of all your successes and failures!