How to Make Your Own Potting Soil

Many home gardeners and do-it-yourselfers are looking for cheaper ways of growing plants. One way to achieve this may be by making homemade potting media. Although this may not result in a cheaper mix, it does offer the opportunity to be creative and to modify mixes for specific goals or plants. The following information will provide you with a basic understanding of potting media ingredients and steps for making homemade media.

Potting media is coarser than garden soil and is commonly used in container gardens and for sowing seeds. The recommended ingredients for potting media have changed over the years as research has found components that are beneficial for seed growth and plant growth.

What is potting soil?

They’re loose and airy, they drain well, and they hold just enough moisture to keep plants healthy without becoming waterlogged. Potting soil is not real soil, it is a soilless mixture of ingredients used to grow plants. All good quality potting mixes have a few things in common such as being loose, airy and able to drain well while still holding enough moisture to keep plants healthy.

• They’re better draining than the average garden soil.
• Potting soil is more lightweight than garden soil.
• It’s easy to handle and consistent.

You can customize your potting soil to match the needs of each plant you are growing by carefully selecting the ingredients and combining them in the correct ratios.

For example:

• Lighter, finer-textured mixes are best for use when starting seeds and rooting cuttings.
• Mixes containing a high percentage of coarse sand or pine bark are best for potted trees and shrubs.
• DIY potting soil with a sandy or grave texture is ideal for cactus and succulent growing.
• When growing a mixture of annuals, perennials, vegetables, and tropicals, the best fit is a general, all-purpose potting mix – one that’s suitable for growing lots of different kinds of plants.

Media Ingredients

You can create either a soil-based or peat-based potting media by mixing different ingredients together.

This text provides recipes for various types of soil and peat-based media, measured in gallons for primary ingredients, and teaspoons, tablespoons, ounces, or grams for smaller ingredients.

• Sphagnum peat moss has a course texture and contributes to good aeration, yet provides water-holding capacity to prevent soil from drying too quickly. Adding too much sphagnum peat, however, can restrict soil drainage by holding too much water. Sphagnum peat moss can be difficult to wet and should be moistened prior to mixing in other ingredients.
• Coarse, sharp, or builder sand, often used in construction, is a primary ingredient in potting media. Like peat moss, sand improves drainage and aeration, but does not improve water-holding capacity. Too much sand will make containers too heavy to move. Sand should not be mixed with clay-based soil.
• Coir fiber is a by-product of the coconut industry. Coir looks and acts a lot like sphagnum peat moss in both commercial and DIY potting soil blends. It has more nutrients than peat moss and lasts even longer, but it’s more expensive to purchase. Coir fiber’s pH is close to neutral. Often sold in compressed bricks, coir fiber is considered by many to be more sustainable than sphagnum peat moss. BotaniCare is one available brand of compressed coir fiber.
• Perlite can be used in both peat-based and soil-based potting media in place of sand. Perlite is expanded volcanic rock (fluoride-based), manufactured when heated to 1,800°F. Like sand, perlite provides great drainage, but is lighter in weight and holds more air. Although more expensive than sand, the advantages may outweigh the additional cost. Disadvantages of perlite include 1) a tendency to float to the top of the medium when watered; 2) an inability to hold or retain water; and 3) a need to be moistened before it is mixed into other ingredients to reduce dust, which is harmful if inhaled.
• Vermiculite is often used instead of perlite. Vermiculite is clay belonging to the mica family and is naturally found in laminated flakes. It expands when folds of vermiculite can hold water, nutrients, and air, unlike perlite. Only horticultural grades, sold at garden centers, are recommended. Vermiculite can easily compact, which reduces its ability to hold water and air.
• Limestone. Add pulverized calcitic limestone or dolomitic limestone to peat-based potting soils to neutralize their pH. Use about 1/4 cup for every 6 gallons of peat moss. These minerals are mined from natural deposits and are readily available and inexpensive. Jobe’s is a good brand of lime for use in DIY potting soil.
• Composted wood chips lighten up potting mixes by increasing the pore sizes, and allowing air and water to travel freely in the mix. They’re slow to break down but may rob nitrogen from the soil as they do, so the addition of a small amount of blood meal or alfalfa meal is necessary when using composted wood chips as an ingredient in DIY potting soil recipes. Use composted wood chips in potting mixes designed for potted perennials and shrubs. To make your own, get a load of wood chips from an arborist and let them compost for a year, turning the pile every few weeks.
• Compost. Containing billions of beneficial microbes, and with superior water-holding capacity and nutrient content, compost is an excellent addition to DIY potting soil. Because it plays such a huge role in promoting healthy plant growth, I use it in all of my general homemade potting soil recipes. But, I don’t include it in recipes for seed-starting as it’s too heavy for young seedlings. I use leaf compost from a local landscape supply yard, but bagged compost from Dr. Earth Compost or Coast of Maine are other favorites.

How to make your own homemade potting soil

Making your own potting soil is an easy way to have complete control over one of the most important steps in the plant-growing process. For gardeners who grow plants in containers, high-quality potting soil is essential. Mixing your own potting soil lets you better provide for the needs of your plants. This results in more stable and consistent growth, and you also save a lot of money.

Make your own potting soil using a combination of the following ingredients. Mix large volumes in a cement mixer or a spinning compost tumbler, or blend the ingredients in a wheelbarrow, mortar mixing tub, or a large bucket if you're making smaller quantities. Be sure to mix everything thoroughly to ensure a consistent result.

6 DIY potting soil recipes

General potting soil recipe for flowers, tropicals, and vegetables

6 gallons sphagnum peat moss or coir fiber

4.5 gallons perlite

6 gallons compost

1/4 cup lime (if using peat moss)

1 & 1/2 cups of a granular, complete, organic fertilizer.

DIY container fertilizer blend:

Mix together

2 cups rock phosphate

2 cups greensand

½ cup bone meal

¼ cup kelp meal

Potting soil recipe for potted trees and shrubs

3 gallons compost

2.5 gallons of coarse sand

3 gallons sphagnum peat moss or coir fiber

2.5 gallons composted pine bark

3 gallons perlite

2 TBSP of lime (if using peat moss)

1 cup of granular, organic fertilizer will be enough to fertilize your plants. If you want to use a DIY container fertilizer blend, 1 cup of the blend will be sufficient.

If you're growing acid-loving trees and shrubs, use 1/4 cup organic cottonseed meal.

Potting soil recipe for succulents and cactus

3 gallons sphagnum peat moss or coir fiber

1 gallon perlite

1 gallon vermiculite

2 gallons coarse sand

2 TBSP lime (if using peat moss)

Potting soil recipe for seed starting

2 gallons sphagnum peat moss or coir fiber

2 gallons vermiculite

1 gallon coarse sand

3 TBSP lime (if using peat moss)

Homemade potting soil for transplanting seedlings

2 gallons sphagnum peat moss or coir fiber

2 gallons vermiculite

1 gallon finely screened compost

3 TBSP lime (if using peat moss)

2 tablespoons of granular organic fertilizer or the DIY container fertilizer blend found above.

Potting soil recipe for houseplants

2 gallons sphagnum peat moss or coir fiber

1.5 gallons perlite

2 cups coarse sand

3 TBSP lime (if using peat moss)

Apply 2 tablespoons of organic granular fertilizer to the soil or 2 tablespoons of the DIY container fertilizer blend.

Making Soilless or Peat-based Potting Media

Soilless mixes or potting media that are based on peat do not contain any soil but generally consist of peat moss combined with horticultural grades of vermiculite and/or perlite and added fertilizer. Peat-based media can be useful for seed germination because they are relatively sterile, light in texture and weight, and uniform. The light texture enables seeds to readily germinate and emerge, allows tender roots to grow, and makes transplanting seedlings easier.

The recipes for Standard Media are created taking into consideration the type of plants that will be grown in it. For example, the media can be different for bedding plants, potted plants or plants that are being grown from seed. To mix ½ bushel basket or four gallons of media:

• Start by pouring two gallons of peat moss into the bushel basket.
• Add two gallons of either perlite or vermiculite and mix thoroughly.
• Moisten the mix before using it in pots or flats.

Adding Ground Limestone and Fertilizer to Soil and Soilless Potting Media

Some ground limestone and fertilizer will need to be put into the media. It is best to mix these ingredients together in another container before adding them to the bushel basket. The fertilizer will provide nutrients, but the pH of the media must be kept in the correct range so the roots can absorb the nutrients. Most plants can use all the nutrients when the pH is between 6.0 (slightly acidic) and 7.0.

Plants held in containers for a long time may need additional fertilizers, while those in soil-based media generally do not. This is because soil-based media usually has a high clay or mineral content, which provides nutrients and the ability to hold water. When making soil-based mixes, the pH should be adjusted according to soil test results. Soil test kits are available for purchase from your county extension office or garden center.

Soil-based and soilless potting media usually need fertilizer even though it may not be required initially. A slow-release complete fertilizer is the best type to use so that nutrients are available for your plants for months.

You should adjust the pH of your soil-based or peat-based media, because it is usually too low (below 6.0). Adding ground calcitic limestone or agricultural lime to your media will raise the pH while also supplying calcium, which strengthens cell walls. Dolomitic limestone can also be used instead of calcitic limestone, and it will raise the pH while supplying magnesium as well as calcium. You can add four level tablespoons of limestone (about 2 ounces or 57 grams) to the bushel basket. Soilless or peat-based media often require the pH to be adjusted upward (to between 6.0 and 7.0) and buffering to prevent rapid drops in pH while the plant is growing. One way to do this is to apply an alkaline fertilizer. You can add two teaspoons (about ½ ounce or 14.2 grams) of potassium nitrate (15-0-15) and the same quantity of calcium nitrate (15.5-0-0) to supply nitrogen and potassium.You can either use slow-release fertilizer or limestone to achieve the same effect.

After fertilizer, limestone, and the primary ingredients have been combined and blended, the excess media should be stored in a watertight container. The media should be sifted through a piece of hardware cloth to break any large clumps into fine pieces before planting or sowing begins.

You can customize your media mix to better suit your needs and situation, now that you have a better understanding of the basics and a recipe for making homemade media. Keep in mind that not all bulk materials are created equal, though. If you choose to use a local source of compost or other alternative materials in your mix, you should then be aware of their nutrient contents and cleanliness. Both factors will affect the success of your plants and experimenting may result in media you consider better than commercially available media, or it may result in poor plant health and death. As the mixer and designer, you are also the one responsible for the results. Good luck and good planting.