Simple homemade soilless potting mix
While not often recognized there is a difference between a soil less potting mix and a sterile soil less potting mix. Not all soil less potting mix ingredients are sterile, in fact there are very few amendments that qualify. If your aim is to provide a safe environment for seed raising then the type of potting mix you use is important.
The traditional soilless potting medium was designed as a sterile growing medium, usually sphagnum peat or more recently coconut coir fiber, and is used instead of soil or other similar products, as a soil substitute for growing plants in any contained environment. The purpose of a soilless potting mix is to give more control over soil-borne diseases, contaminates and many other problems that plagues potting mixes containing other materials.
Soil or garden loam comes with a range of problems and are the main reason why over fifty years ago these potting mediums were developed. Young plants, especially seeds and young seedling, that are confined in seed cells and pots are particularly vulnerable to many of these problems.
The boundaries between a soilless mix and a sterile soilless mix are commonly crossed without any thought to what is being done. Many potting mix ingredients, even some of the better ones, are considered soilless but they are not always sterile.
Photo left - Exploring alternative methods and materials is part of the enjoyment of gardening and different potting mix recipes is no exception. When using soil less potting mix ingredients that are not sterile it should be remembered that the problems gardeners had using growing mediums, like compost, soil, wood products, leaf mould and similar ingredients, before the advent of the soilless potting mix will be no less a problem today. There is always an element of risk, when adding these ingredients to a potting mix and they will need to be treated differently to the traditional sterile soilless ingredients. Follow this link for more on what’s what with potting mix ingredientsMouse over image to enlarge.
For those new to seed raising the safer approach is to use traditional sterile soilless potting medium or at least use them for a portion of the seedlings being raised while experimenting with alternative ingredients. With the proper care either method will produce the desired results.
You cant talk about soilless mixes without including some of the many pre made seed starting pellets and blocks.
Photo Left One - Growing seedlings using sphagnum peat pellets are an excellent way for a novice or someone with limited time and space to raise their own seedlings. Mouse over image to enlarge.
Photo Left Two - Young Radicchio seedlings - These pre-made compressed seed starting pellets are independently wrapped to retain the soil making them easily moved around without disturbing the seedling. Mouse over image to enlarge.
A bio sponge is plug of sterile medium with a hole in top made for germinating one seed, there are a number of different sizes
Photo Right - They are excellent for maintaining aeration and water retention, and as seen here allow the roots to freely penetrate the sponge.Mouse over image to enlarge.
Growing seedlings using coconut coir fiber pellets is similar to using sphagnum peat pellets. Simply add water, watch them swell, and sow your seed.
Photo left - Coir pellets are held together with either bio-degradable netting or some with paper wrap which will not fall apart but still allow the roots to penetrate the sides. Mouse over image to enlarge.
It is not a simple job buying a soilless potting mix. It can be confusing picking out a bag of soilless potting mix from the many different types and labeling used. Unfortunately very few potting mix labels will contain the words “soilless” or even “soil less”.
The best a gardener can do when looking for the product they want is to properly read and assess the label or list of contents. Knowing what each ingredient in a potting medium is and how it acts and affect the potting mix is helpful. For more details on many of the ingredients common to potting mixes follow this link potting mix ingredients.
When looking for a potting medium for starting seeds, ensure the packaging stipulates for starting or germinating seed.