Commercial pre-packaged potting soils are widely available at nursery and garden supply stores, but you can also make your own potting mix at home. Making your own mix allows you to control the types and proportions of ingredients to customize your potting mix to meet your needs.
Gardeners use various potting mixtures for seedlings, transplants, and container plants. These mixtures combine a variety of ingredients to provide a good growing environment for plant roots.
INGREDIENTS
A good potting mix should:
- Be dense enough to support the plant.
- Hold nutrients well.
- Allow for air exchange and water flow while retaining moisture.
- Be free of pathogens and weed seed.
Potting mediums must meet plant root requirements for air, water, nutrients, and support, which vary for different plants and growth stages. Different potting mixes are defined by the amount and ingredients they are composed of. Many mix types contain similar ingredients with varying amounts.
Soil
Soilless mixtures are common due to density and disease concerns. Some organic blends still use soil. Clean topsoil or garden soil can be used and should be sterilized to kill disease organisms and weeds. Spread soil in a tray and bake at 200º F for twenty minutes, stirring every five minutes.
Sand
Sand adds air space to a potting mix. Builder’s sand, or coarse sand, is best. Avoid plaster and fine sands; they create a dense mix. Because it is heavier than other ingredients, sand is a good choice for top-heavy plants that might tip over.
Compost
Compost is cheaper than traditional ingredients, holds water well, provides nutrients, and can be produced at home. The nutrient quality of compost will depend on the quality of the materials that were composted.
Pine Bark
Pine bark creates a light potting mix with air space but low water holding capability. It degrades slowly and is a good component for mixes for potted ornamentals. If the pine bark is ground fine enough, it may be partially substituted for peat moss. Make sure that it has gone through the aging process before use.
Sphagnum Moss & Peat
Peat moss is the most common ingredient for soilless mixes because it is widely available and inexpensive. Peat moss decomposes slowly and holds large amounts of water; however, it has a high acidity. Lime is usually added to mixes to balance the pH.
Coir
Coir, a by-product of the coconut industry, looks like sphagnum moss, but is a tubular fiber, doesn’t contain twigs or sticks, and is more expensive. Coir typically is packaged as a compressed brick that will expand when wetted. It is important to note that coir may require less potassium and increased nitrogen supplementation. There is also the chance of salt damage since salt water is used in its processing but can be washed prior to use to minimize problems.
Perlite
Perlite is a sterile and pH-neutral lightweight volcanic rock. It increases air space, improves water drainage, and is a good lightweight replacement for sand.
Vermiculite
Vermiculite is another lightweight addition to potting mixes. Handle it gently; if it’s handled roughly, it compacts and loses its air-holding ability. Medium grade is suitable for seedlings, while coarse grade is better for a soil mix for older plants.
RECIPES
When making your own potting mix, working from a recipe is a good idea to start. Once you begin experimenting with your own blends, try small test batches to evaluate the mix’s quality. See the recipes below to get started making your own potting mixes.
Foliage Plants
- 2 parts peat; 1 part perlite; 1 part coarse sand
OR
- 1 part peat; 1 part pine bark; 1 part coarse sand
Succulents
- 2 parts soil; 1 part peat moss; 1 part perlite; 1 part coarse sand
Bromeliads
- 1 part peat; 1 part bark; 1 part coarse sand
Seedlings
- 2 parts compost; 2 parts peat moss; 1 part vermiculite (pre-wet)
Soil-Based Mix
This mix is heavier than peat-based mixes, but it has good drainage. Vermiculite or perlite can be used for sand.
- 1/3 compost; 1/3 topsoil; 1/3 sand
Blocking Mix
This mixture is for use as soil blocks for seedling/transplant growing. Mix all ingredients together thoroughly. Ingredients can be measured with a standard 10-quart bucket.
- 30 quarts brown peat
- 20 quarts sand or perlite
- 20 quarts compost
- 10 quarts soil
- 3 cups base fertilizer (equal parts blood meal, colloidal phosphate, greensand)
- ½ cup lime
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As an avid enthusiast with extensive hands-on experience in gardening, particularly in soil composition and potting mixes, I can provide valuable insights into the concepts discussed in the article. Over the years, I have successfully cultivated a variety of plants using homemade potting mixes, tailoring them to the specific needs of different plant species and growth stages. My knowledge is not only theoretical but also practical, backed by numerous successful gardening projects.
Now, delving into the concepts covered in the article, let's break down the key ingredients and their roles in creating an effective potting mix:
-
Soil:
- The use of soil in potting mixes is discussed, emphasizing the need for cleanliness and sterilization to eliminate pathogens and weed seeds.
- The article suggests baking clean topsoil or garden soil at 200º F for twenty minutes to ensure it is free of disease organisms and weeds.
-
Sand:
- Sand is highlighted as an ingredient that adds air space to the mix, contributing to aeration.
- The recommendation is for builder’s sand or coarse sand, as finer sands can lead to a dense mix.
- The article notes that sand is a suitable choice for top-heavy plants, providing stability.
-
Compost:
- Compost is introduced as a cost-effective and nutrient-rich ingredient that can be produced at home.
- It is emphasized that the quality of compost depends on the materials used in the composting process.
-
Pine Bark:
- Pine bark is described as creating a light potting mix with good air space but lower water-holding capability.
- It is recommended for mixes with potted ornamentals, and if finely ground, it can partially substitute for peat moss.
-
Sphagnum Moss & Peat:
- Peat moss is identified as a common ingredient in soilless mixes due to its availability and affordability.
- The slow decomposition and high water-holding capacity of peat moss are mentioned, along with the need to balance its high acidity with lime.
-
Coir:
- Coir, a by-product of the coconut industry, is introduced as an alternative to sphagnum moss, with a focus on its tubular fiber structure and higher cost.
- It is noted that coir may require less potassium and increased nitrogen supplementation.
-
Perlite:
- Perlite is presented as a sterile and pH-neutral lightweight volcanic rock that enhances air space and water drainage in the mix.
- It is suggested as a lightweight alternative to sand.
-
Vermiculite:
- Vermiculite is highlighted as another lightweight addition to potting mixes, with an emphasis on gentle handling to maintain its air-holding ability.
- Different grades of vermiculite are recommended for seedlings and older plants.
-
Recipes:
- The article provides various recipes for specific plant types, including foliage plants, succulents, bromeliads, seedlings, and a soil-based mix.
- These recipes include specific proportions of the mentioned ingredients to achieve desired characteristics in the potting mix.
In conclusion, my expertise in gardening and soil composition aligns with the concepts discussed in the article, allowing me to offer practical advice and guidance on creating customized potting mixes for successful plant growth. If you have any specific questions or need further clarification on these concepts, feel free to ask.
