There are some home gardeners who are content to buy bags of Miracle-Gro from Walmart. But that’s not you, is it?
You’ve been in the gardening game long enough to want something more. You want to save money, absolutely. But more than that, you want control. You want to know exactly what you’re feeding your precious plants.
You’ve reached a point of no return, but don’t worry–I’ve got you! What follows is my tried-and-true recipe for homemade potting soil, along with several variations for different plants and planting scenarios.
Store-bought potting soil is made of four main ingredients: peat moss, pine bark, perlite, and fertilizer. You can easily make your own potting soil at home and incorporate far more beneficial amendments for your plants. Making homemade soil mix is time-consuming, but it’s worth the extra effort. By making your own potting soil you will save money and be able to control exactly what elements are in your mix. Once you have the basic recipe down, you can make small adjustments to suit your plants’ specific needs.
Intrigued? Read on to learn about the secret ingredients to GreenUpSide’s potting soil recipes.
How To Make Homemade Potting Soil Mix (From Scratch!)
Before we start throwing things together and mixing, you need to understand what’s going in your homemade potting mix and why.
Homemade potting soil mix, whatever the variation, is usually comprised of some combination of the following nine ingredients.
- Sphagnum peat moss
Peat moss is the base of nearly all potting soil mixes, store-bought or homemade. Peat moss works well as a base, as it is a fluffy, soil-less medium that holds water and provides aeration.
Peat moss tends to be acidic, and lime is usually added to mixes containing peat moss at a rate of ¼ cup lime for every 6 gallons of peat moss. Peat moss may also be slightly hydrophobic–meaning that peat moss resists water initially.
You can easily remedy this problem by moistening the peat moss slightly before mixing it with other ingredients.
Peat moss, while it is an incredible growing medium for plants, is formed from organisms dying in bogs over millions of years. This process takes so much time that peat moss is technically a non-renewable resource.
Today, Sphagnum peat moss mined from bogs in Canada has become an environmental issue, as the processes that produce horticultural-grade peat moss are not sustainable. Activists are urging gardeners and potting soil producers to look for another equivalent.
Fortunately, there is an alternative to using peat moss in homemade soil mixes.
- Coir fiber
Coir fiber has a similar consistency to peat moss, and is harvested from coconuts. Coir fiber is more expensive than peat moss, but some would argue that it is a more sustainable base for potting soil mixes.
Coir fiber isn’t as nutrient-rich as peat moss, and it’s a good idea to soak coir fiber before using it to wash away some of the saltwater accumulated during the manufacturing process.
Coir fiber retains water and is heavy enough to hold the weight of a growing plant. Its fibers provide a growing medium to strengthen young taproots and allow for ample drainage and aeration.
Limestone is mainly added to potting soil mixes to balance the acidity of peat moss. As previously mentioned, add ¼ cup lime for every six gallons of peat moss.
Limestone is fairly inexpensive and comes in two strains–calcitic and dolomitic. Dolomitic lime contains more magnesium than calcitic lime.
Perlite is a volcanic rock often used to improve drainage in potting soil mixes. Perlite promotes aeration and increases soil porosity–without adding much weight.
Horticultural perlite is somewhat expensive but it is sterilized and readily available at most garden or farm supply stores. Perlite is a great addition to potting soil mixes because of its neutral pH.
Like peat moss, perlite is hydrophobic and needs to be pre-moistened before being mixed with other ingredients.
Vermiculite is a nutrient-rich, expanding clay that retains water and air in potting soil mixes. Vermiculite adds calcium and magnesium to the mix, essential nutrients to enhance plant growth.
Vermiculite is a super mineral that also serves to increase soil porosity.
For more information on perlite and vermiculite, check out my article comparing the two here.
- Coarse sand
Coarse sand is an inexpensive material used in potting soil mixes to increase drainage and add weight. Sand has little nutritional value, but is especially beneficial for cacti and succulents, as it resembles these plants’ native terrain.
Larger plants benefit from a mix with more sand, as the sand serves to anchor their roots below the soil.
No homemade potting soil mix is complete without the addition of fertilizer. The best thing about making potting soil yourself is that you can control what fertilizers you use and exactly how much.
I choose organic or all-natural fertilizers over synthetic whenever possible because I don’t want myself or my plants exposed to manufactured chemicals. Most organic gardeners recommend using some combination of these five elements:
- Rock phosphate
- Seaweed extract
- Azomite (trace minerals)
Start by mixing equal parts of these five ingredients. Adjust amounts as needed once you learn what your plants respond best to.
- Wood chips
Composted wood chips function like pieces of pine bark in store-bought potting mixes–to increase porosity in the mix. If you use wood chips from a local source, make sure that they have been aged for at least one year prior to incorporating into the mix.
Wood chips have their benefit in a homemade potting soil mix, but they do draw nitrogen away from the plants. Supplement your mix with blood meal or alfalfa if you opt to use wood chips.
Compost is the golden ingredient in homemade potting soil mix. Compost is composed of organic matter, so it is rich in nitrogen, phosphorus, and potassium, among other nutrients.
Compost is full of beneficial bacteria and other microorganisms, and has the added benefit of water retention.
The beauty of incorporating compost into your own potting soil mix is that you can choose where you source your compost. Be sure to use compost that has been professionally processed, or use local compost that you know has been heated to at least 140 degrees Fahrenheit to sterilize the compost from weed seeds, fungal diseases, and bad bacteria.
One note about compost–don’t incorporate compost into seed-starting mixes. Compost is too heavy for seed starting and is more likely to grow green mold (algae) that seedlings can’t outcompete for sunlight and water. (See my article on green mold here.) Save compost for older seedlings and more mature plants.
Now that we’ve identified the nine key ingredients of homemade potting soil, let’s get started mixing!
All-purpose Potting Soil Mix For Flowers & Vegetables
I like to use a recipe from Virginia Highlands Community College’s horticultural program for annuals. This recipe encourages vegetative growth and pushes the plants to flower and fruit come harvest time.
This recipe uses a five-gallon bucket to measure peat moss and compost, and a smaller, 5 ounce Dixie cup to measure other ingredients.
- 3 buckets of screened peat moss
- 0.5 Dixie cup lime
Moisten these ingredients, then mix together
- 2 buckets vermiculite
- 3 buckets screened compost
- 1 Dixie cup blood meal
- 1 Dixie cup bone meal
- 1 DIxie cup trace elements
Mix these ingredients together, then add water
Be sure to wear gloves and a mask when mixing these ingredients. While this is an organic recipe, try to avoid touching these concentrated substances with bare skin and avoid breathing in any dust produced during the mixing process.
This mix produces a little over 40 gallons of homemade potting soil mix. If that’s a little more than you need, cut this recipe in half or quarter it. This is a great all-purpose potting soil mix that suits a variety of flowers and vegetables.
If you’re serious about making your own potting soil from scratch, it might be worth investing in a portable cement mixer. These spinning mixers are a lifesaver for those of us making multiple batches of potting soil! There are some models on Amazon for under $200. Harbor Freight carries cement mixers as well.
Animal troughs also work well for mixing large quantities of potting soil. If you scale this recipe back, you may be able to mix everything together in a wheelbarrow or garbage can. Regardless of where you make your mix, be sure to mix all the ingredients together thoroughly and moisten before using.
I love this general-purpose potting mix, but some university extension offices have come up with other variations if you’re interested in using different mixes for your specific plant needs.
Potting Soil Mix For Houseplants
Houseplants may not need quite as much care as annuals, but indoor plants do benefit from a well-draining potting soil with a few added nutrients. Cornell University’s recipe for foliage plants is as follows:
- ½ bushel sphagnum peat moss
- ¼ bushel vermiculite
- ¼ bushel perlite
- 8 tbsp. ground dolomitic lime
- 2 tbsp. superphosphate
- 3 tbsp. 10-10-10 fertilizer
- 1 tbsp. iron sulfate
- 1 tbsp. potassium nitrate
One bushel is equivalent to about 9 gallons. So ½ bushel is around 4 ½ gallons and ¼ bushel is about 2 ¼ gallons. When it’s time to bump up your houseplant to a bigger pot, whip up a batch of this mix and your plants will thank you!
For a simpler mix, Clemson University recommends using 2 parts pine bark, 1 part peat, and 1 part sand. Just be sure to apply a liquid fertilizer regularly, as this mix has little nutritional value.
Potting Soil Mix For Succulents & Cacti
If making a soil mix specific to succulents and cacti, incorporate more sand than you would in other mixes. The University of Florida recommends
- 2 parts sterilized garden soil
- 1 part peat moss
- 1 part perlite
- 1 part coarse sand
Sterilized garden soil is soil that has been heated to kill off any weed seeds or fungal spores. To sterilize soil at home, simply bake a sheet pan’s worth of moist garden soil in the oven at 250 degrees. Use a food thermometer to make sure that the soil temperature reaches 180 degrees, and cook for 30 minutes.
High organic material is essential for flowers and vegetables to thrive, but cacti and succulents can live without it. Steer clear of added fertilizers in cacti and succulent potting mix, as fertilizers run the risk of doing more damage than good to these plants that prefer poor soil.
While potting soil mixes geared for other plants might retain moisture, desert-dwelling plants need a mix that drains well and prevents root rot.
Seed Starting Mix
Store-bought seed starting mixes tend to be finer-textured and significantly less dense than potting soil mixes. To make your own seed-starting mix, Oregon State Extension suggests
- 1 part sterilized garden soil
- 1 part peat moss
- 1 part perlite or sand
Many seeds actually need light to germinate, so a fluffier mix will allow light to come through the top layer of soil to reach the seeds. Compost, peat moss, and vermiculite all retain water, and consistent moisture is crucial to seed starting.
Notice that seed starting mixes don’t require fertilizer–seedlings need to have two sets of true leaves before they are ready to metabolize additives.
Making potting soil from scratch is not nearly as hard as you’d think. Think of it as an experiment and adjust these recipes to meet your garden’s specific needs.
Making your own potting soil can save you money in the long run, while also allowing you to control what your precious plants are feeding on.
Make a statement for the environment (and empower yourself) by making your own potting soil mix at home!
I hope you found this article helpful. If so, please share it with someone who can use the information.