Below is a brief article about potting soil components "perfect potting soil" written by jill slater: a reporter for KGO TV in San Francisco, California
Perfect Potting Soil
Do you prefer the sweet taste of chocolate or does something salty "wet your whistle?" Maybe you enjoy the sour of lemon or a smooth yogurt shake. We all have our own tastes that make us happy. It's the same with plants.
For instance, some plants, such as orchids, grow well in bark and peat moss, while cacti thrive in compost and sand. Because different plants have different soil requirements, it's important to plant them in a growing medium tailored specifically for their plant culture.
The first step in knowing what to combine to make an efficient potting soil is understanding what each component does in the mixture. All potting mixes are blends of various organic compounds that can provide good aeration, drainage, water retention, and that add or delete weight from mixtures.
There are many good packaged soils on the market, so you might question the need to make your own. Making your own soil is a bit like making a seasoning from scratch, verses buying a package of mixed seasonings. Creating custom soil, like seasoning, gives the Good Gardener more control and hopefully success, in the growing process. The knowledge and of what works best to house specific plants, and why they work, reins supreme.
The following is a list of basic ingredients that go into making all kinds of potting soils:
Top Soil: Soils are the combination of organic materials, microorganisms and spaces filled with water and air. All soils have different compositions. The proportion of large and small particles affects how well the plant grows.
Garden Compost: An organic material rich in decomposed plant and animal remains.
Peat Moss: Sphagnum peat moss is the result of ground up reeds, mosses and grass found in bogs. Its moisture-retentive nature is important for good soil. Although peat absorbs water well, it is nearly impossible to re-wet. It is also a prized natural resource and should be used sparingly. Good Gardeners interested in preserving peat bogs should use coconut fiber, ground bark or coir dust instead. Coir dust will not help acidify soil as peat does.
Perlite: Perlite is derived from volcanic glass that has been heated to temperatures over 1000 degrees. Perlite is used to provide aeration, (provides the air spaces necessary in a growing medium), increases drainage and lightens the weight of potting mixtures. It does not absorb water. The white substance that floats to the surface of wet soil is perlite.
Pumice: Pumice is a crushed form of volcanic rock. Pumice insures good drainage and aeration. Like perlite it lightens the weight of mixtures. Pumice is heavier than perlite and does not float to the top of wet soil.
Vermiculite: Vermiculite is derived from mica by heating it to more than 1000 degrees. Like perlite it helps with aeration, but unlike perlite, vermiculite absorbs water readily. Due to its sponge-like nature, vermiculite needs to be replaced, as it will eventually become compacted. Vermiculite is chemically reactive and binds and releases minerals.
Sand: Sand adds weight to mixtures and stabilizes pots. Sand also improves drainage and aeration. Only use coarse sand in potting mixtures, as fine sand does not allow air and water to flow through potting mixtures.
Fir Bark: Redwood bark is aged and then chopped into chips of varying sizes. Fir bark holds water well, and therefore, easily enables the delivery of water and air to plant roots.
Charcoal: Only use horticultural grade charcoal. Charcoal is used to absorb salts found in water and fertilizer.
Macronutrients and Micronutrients: Bonemeal, bloodmeal, lime etc. These chemicals are often added to soils in small quantities. They either contribute to the pH balance or provide essential minerals. Time released fertilizers such as Osmocote, will provide a slow release of nutrients (nitrogen, phosphorus and potash) that fertilize the plant over a period of time.
Perfect Potting Soil Recipes:
Each of the following recipes have been handed down by friends. Both have been used with good gardening results.
Gayle Taylor's Potting Soil for Indoor or Outdoor Plants:
3 parts peat moss or coconut fiber
2 parts perlite
2 parts bagged potting soil
1 part vermiculite
1 part course sand
¼ part charcoal
To 1 gallon of mixture add:
1 cup bonemeal
5 Tablespoons Dolomitic lime (used to balance the acidity of soil mixture)
14-14-14- Osmocote time released fertilizer (follow directions on package)
Tom McNally's Cacti Potting Mix:
3 parts pumice
1 part compost
1 part coarse sand
1 part perlite
Happy Gardening,
Jill Slater
