Plant Nursery Potting mix, make your own!

Potting mix, making your own at a low cost is a key skill in running even a small plant nursery. You are going to use a lot of potting mix. You want a great mix you can make at a reasonable cost. This is part 4 in our series on How To Start A Plant Nursery. We are here to help you get your plant nursery started without breaking the bank.

How to make a great potting mix at an economical cost.

This is a question we can’t fully answer as the answer varies, The main factors are:

What are you growing?
Where do you live?
How much soil mix you need?
Are you able to transport bulk materials or have them delivered.

What is in a potting mix you make or buy?

Generally the mixes you buy or will want to make do not contain soil. Soil is defined generally as “Soil, also referred to as earth, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support the life of plants and soil organisms.”

The mixes you buy or might make may contain some or all of the elements of “soil” but are not naturally occurring mixes. You can’t just dig a proper soil mix up out of the ground! Mixes that are made are considered soil-less mixes. That said you could go out in an undisturbed location, dig up some “soil” add some amendments and make a good potting mix.

To make your soil mix, you will want to focus on gathering what you can locally. You will also want to try to buy in bulk. If you have a wheel barrow or plastic tub, you can certainly mix it yourself. Avoid store bought mixes, they are very expensive. Also avoid ANY product that comes with fertilizer in it. We only use slow release fertilizers and can add them very economically ourselves.

What are the needed components of a good general Potting Mix?

You want 3 main components in a soil mix that you make yourself. First is a water or moisture holding material. You want to maintain a moist environment around the roots of plants. Although you want to retain some moisture you need some drainage so your plants aren’t sitting in a pot of water. Lastly even though you will use slow release fertilizer, you could have a component of organic matter in your soil mix. This is to help nourish your plants and provide some needed minerals.

What are good moisture retaining materials for a Potting Mix?

Sphagnum Peat Moss – Long used in potting mixes, Peat Moss is great at holding moisture, lightening up your mix and it is readily available. The cost of Peat Moss is not inexpensive but not cost prohibitive either. It can hold up to 20 times it’s weight in water. Peat Moss however is hydrophobic thus, when it gets too dry, it actually repels water until slowly hydrated. (For those concerned about the sustainability of natural Peat Moss can read this interesting article: The Truth about Peat Moss

Coco Coir – (Pronounced Coco Core.) “Coir, also called coconut fiber, is a natural fiber extracted from the outer husk of coconut. Coir is the fibrous material found between the hard, internal shell and the outer coat of a coconut.” Coir can also be ground into a “Peat” type consistency and will allow your potting mix to retain some moisture over time. Coco Coir is a great component to a potting mix but it is generally too expensive for even a small nursery grower. It is a byproduct or a waste but has to be processed and then shipped across the globe to get to the USA.

Soils and Materials That Drain Well

Screened Top Soil – Typically a soil that is rich in organic matter. Often contains decayed bark, wood, vegetative material and even decomposed manures. Can be a good and inexpensive base material for your potting mix. Top soil can be mixed with bark, Perlite or vermiculite to ensure adequate drainage.

Sand – Good course sand, often called mason sand, can add drainage to your soil mix. Sand is available almost anywhere in either bags, pickup in bulk, or delivered by truck. Its in the $15 to 25.00 per yard range, delivered if you buy 6+ yards. You can also go to many supply yards and buy a yard or 2 dumped in your pickup truck or trailer or buy it by the bag. We have successfully used a mix of 2 parts sand with 2 parts humus and 1 part Perlite.

Perlite – Is made from volcanic rock, is light, helps retain some moisture and helps aerate soil mixes. Perlite is found in many professional potting mixes and makes yours look more professional as well. We use 10 to 20% in almost every mix we make. We use it in our cutting rooting mix at a rate of 2 parts Perlite and 1 part sphagnum peat moss.

Pea Gravel – While not that commonly used, pea gravel can add some drainage to a potting mix. Much like Perlite it helps aerate and retains some moisture too. You may have access to some low cost pea gravel or even small, yellow beach stones. Try it at about a 10% ratio with other materials!

Barks and Organic Materials including some that drain well.

Finely ground Softwood Barks

Pine and fir barks that are ground very finely can be an excellent potting medium by themselves or mixed with other ingredients to make a great potting mix. Finely ground barks or fines, drain well and provide good root/plant support. In addition as they decompose the will provide good nutrients for most plants. They are light and easy to work with.

Pine and fir barks are available very inexpensively in areas such as the South and Pacific Northwest. Search online and also call saw mills as this is where bark is removed from logs and becomes almost a waste product. Some saw mills may allow you to come to the mill and they will load your truck or trailer. Generally the cost is very reasonable, $10 to $20 per cubic yard. In certain parts of the USA the pine and fir barks are very difficult to find.

Hardwood Bark

Available in locations such as the Northeast, Hardwood Bark can be a great component for your potting mix. You should buy what is called double or triple ground bark. The bark, commonly used as a plant much needs to be nice and fine to use in a potting mix. If you can, buy your hardwood bark months ahead and let it start to decompose. We often scrape old bark out of shrub beds to use in our mix and then apply the newer mulch to the beds to dress them up. Hardwood bark is available in bulk from saw mills and also in bulk at supply yards for pick up or delivery. We pay $20-25.00 per yard, delivered.

With any bulk bark material make sure of the following. Make sure materials you use is not treated with any chemicals or dyes, do not use these. Make sure the bark does not contain a lot of wood. Too much decomposing wood is not great for a potting mix. Absolutely avoid wood chips in your potting mix, OK to use as a top dressing but not in the mix.

Add Organic materials to your potting mix

General compost or humus – decomposed leaves, grass and other vegetative waste. Well decomposed humus is a great base for a potting mix. Humus is available by the bag, by the yard, and in some areas by the truck load. Our local county and maybe your town or county may have a vegetative waste program where they may offer humus for free or purchase. We buy 10 yards of screened humus at a time.

Check around, municipalities who collect leaves or grass clippings often offer humus. Some call it “Leaf Mold” which would be unscreened material and not fully decomposed. If you collect this in advance, keep turning it over, it will decompose down to a humus. This is worth the effort, especially if the material is free.

What you should not use in a potting mix

Never use any pre-made potting mix that contains fertilizers. As mention you should always use a slow release, commercial fertilizer. Bagged soil mixes with fertilizers will burn your plants.
Wood chips from a tree service are often available for free but are not a good ingredient for a good potting mix. Wood chips make an excellent top-dressing or mulch for plants. We use them like crazy for this purpose. However, wood chips mixed into your potting mix can rob the mix of nitrogen as it is consumed by the decomposing wood. Not to be confused with bark, decomposing wood is not for your potting mix.
Be careful with hardwood bark sold as “Mulch.” Much of it is just hardwood bark but some process it with a lot of wood (See wood chips) or use dyes. Verify you are getting hardwood bark only.
Some top soils are not as organic as you might think. Some bagged products and some bulk top soil is actually made of some organic material but may contain some previously contaminated soil that has been baked. You want to be a little careful here but no paranoid. Read the bag.

Some great formulas.

In the South or Pacific Northwest

In this area try to find a saw mill or a source for softwood bark. You can use this straight as long as it is finely ground. If not, buy or get it a year in advance. Let it decompose, preferably turning it every few months.

To softwood bark you could also add course sand, perlite, humus, pea gravel, hardwood bark, or screened topsoil. You would do this if you can source the ingredients inexpensively in bulk.

Potting Mixes for the North East

You would not want to use any one ingredient in the North East. Top soil is too heavy, humus can pack down, just sand alone can turn to almost concrete. Here are some mixes we have tried.

2 parts humus, 2 parts course sand, 1 part Perlite. – Drains well, has a good organic component and can be purchased in bags or truck loads. We buy in bulk and produce this mix for about $30.00 per cubic yard.
2 parts humus, 2 parts hardwood bark, one part perlite. This is our current preferred soil mix. It is a nice light mix, we can buy the humus and bark at around $20-25.00 per yard. We buy the perlite in 4 cubic foot bags delivered for Cost buying in bulk is also about $30.00 per cubic yard. One finished yard will fill
2 parts screened top soil, 2 parts sand or hardwood bark, 1 part perlite. This is a great mix if you can’t find humus and in bulk will cost around $30.00 per cubic yard.
2 parts Sphagnum Peat Moss or Coco Coir, 2 parts (Screened top soil, sand, hardwood bark, or humus) 1 part perlite. This is a great mix if you can find some ingredients in bulk but not all. Buying some ingredients in bulk will cost around $40.00-60.00 per cubic yard.

How much potting mix do you need.

We found this guide to determine how much potting mix you need to fill your pots, by the yard. Nursery Pot Fill Volume Guide. For reference a cubic yard is 3 feet X 3 Feet X 3 Feet or 27 cubic feet. If you are buying materials by the bag, they will come in measured in cubic feet. You will have to convert to cubic yards. For example if we want to add 20% perlite to our potting mix the formula is. 27 cubic feet X 20% = 5.4 cubic feet per yard of finished mix. We simplify that by adding 10-12 bags of perlite for each 10 yards of finished mix.

From the guide we see a yard of potting mix will fill about 60, trade 3 gallon containers or about 200, trade 1 gallon containers. For this series How to Start a Plant Nursery we are going to grow 500 plants. Therefore, you will need about 2 1/2 yards of potting mix to fill 500 trade 1 gallon pots. While that isn’t a lot of material if buy in bulk, it is a lot of 2-4 cubic yard bags. Try to buy one, if not all of your potting mix ingredients in bulk.

Nursery mixes – the possibilities are endless

We have tried to give you a lot of ideas so you can create an inexpensive potting mix yourself. Buying pre-made bags is going to become very expensive over time. You want to experiment and try what is available locally, in bulk quantities. Happy Potting!

Our Plant Nursery Start Up Series

How to Start a Plant Nursery – With super low start-up costs.
How to Get Free Plants – Your secret start up advantage
Propagate Plants All Year – Always be propagating
Make Your Own Potting mix – Inexpensively for your nursery
Propagate plants by Dividing A Great Way to Increase your Nursery Plant Inventory