Developing A Good Potting Soil Mix Is Key
As a collector of Japanese maples, and one that enjoys growing most of them in pots, I needed a simpler soil mix to make and one that would still satisfy the needs of my Japanese maples. It was becoming time consuming to gather items for the so called 'Perfect Mix Recipe' and the expense of materials including mulch, potting soil, sand, peat moss, pumice, perlite, soil sulfur, gypsum, etc., lessened the chance to purchase another maple in the next decade. Many of the items listed in the Japanese maple mix recipes are already contained in the planter mixes and top soils that can be purchased easily at you better nurseries and garden centers. By combining a few of these products for your soil mix you can provided your Japanese maples with the water, air, nutrients, and stability they need to grow well in pots or containers. Additional nutritional items or elements found to be deficient can always be added later without changing the basic mix.
Your Japanese Maples vitality starts with the health of its root system. The planting soil mix is the foundation for building a strong root system which in turn will help to develop a healthy tree. The most important function of a good basic soil mix is one that will be well draining. Japanese maples like moist not wet soils. Wet feet, root rot, is the most prevalent killer of Japanese maples. The second function of a good mix is moisture and nutrient retention. The mix has to have the ability to retain the moisture and nutrients applied in order that the roots can absorb them and distribute these to all parts of the tree. The third function of a soil mix is to act as support or stability for the root system. This is providing the ability to make nutrients readily available to the roots and to store nutrients that will become available in the future. The stronger the root system the more support also they will be in acting as a strong foundation or support for the tree in inclement or windy conditions.
Keep in mind a few things I had learned before choosing materials for your mix. It is best not use garden soils. Garden soil can contain soil born pests, diseases, and smaller particles as in clay soil that will become compacted hindering the mixes draining ability. Garden soils are also heavier and adds to the potted plants weight more than need be. I also elect not to use planter mixes or top soil mixes that contain fertilizers. These planting mixes are formulated for general overall garden plantings and may not have the best of nutrient percentage for a healthy Japanese maple. Japanese Maples are slow growing and forcing growth with high percentages of nutrients especially nitrogen can harm the trees natural characteristics such as size and color. Too high a level of Nitrogen can also burn roots damaging or killing the tree. I also stay away from potting mixes and soils that contain chicken or cow manures as they can be too hot, concentrated nitrogen, and burn the roots also if not highly composted. The Japanese maples require very little fertilization. Because of this I would rather feed my maples with nutrients when I feel they are needed.