A friend returned home from vacation with a 10-inch palm tree for her mother’s apartment. She searched everywhere for a “soilless mixture” to repot it in, per the package instructions. Ultimately, a bag of shredded bark was purchased, often used in growing orchids. Good for orchids, not so good for palm trees. The plant didn’t survive.
Unfortunately, my friend thought the large bag of potting mixture in her garage earmarked for outdoor containers was “soil.” A close examination of the ingredient label would have revealed that it was, indeed, a soilless mixture. These are widely used for seed starting and container growing as the mixes are disease free, light in weight, and blended with ingredients that provide the right amount of aeration and moisture retention for plant roots.
General purpose container mixtures combine sphagnum peat moss, bark and vermiculite and/or perlite. These are sold under a variety of names, but never include the word “soil.” Peat moss is a light-weight growing medium that is good at holding moisture. Bark adds another bit of organic matter and texture to the mix. Vermiculite and perlite help the mix to retain water, with perlite also assisting with aeration.
Garden soil, straight from a bag or from your yard, doesn’t have these good qualities once placed into a container. Both drainage and aeration will be quickly lost and plants will grow poorly or not at all. The University of Illinois Extension successful container gardens website suggests that garden soil can be used as a container media, but only if amended. Mix one part garden soil, one part peat moss and one part perlite or coarse builders’ sand. Don’t use fine beach or play sand.
The website notes the advantages and disadvantages of this soil mix. An advantage exists with containers used in a windy location where the extra weight will help keep the pot upright. Soil-based media are also a bit more forgiving when it comes to water and fertility. They tend not to dry out as fast, and they also tend to hold on to nutrients longer. The disadvantage is that the soil you are using may contain insects, weed seeds and disease organisms. Soilless mixes are generally free of these things.
Email your home garden and lawn questions to firstname.lastname@example.org or call the Master Gardener Helpline at 630-955-1123. Visit our website at http://web.extension.illinois.edu/dkk/.
Julie Moore has been a master gardener volunteer with the University of Illinois Extension in DuPage County for 10 years and has a degree in ornamental horticulture from the University of Illinois.Tags: Gardening