Bonsai trees are often viewed only for their shape and the arrangement of their garden. In order to have the leaves and substance to be formed into desired shapes, the bonsai tree or plant has to be vibrant and healthy enough to undergo the changes and the potential trauma to their branches and leaves. Although the goal is aesthetic, to be reached, the preparation has to be much more practical.
A bonsai tree has specific needs, and every type of tree and individual situation needs customized attention to thrive. The gardener has to become familiar with the species and type of tree he is working with and the light and planting needs of that breed. Then, they have to be attentive to their individual tree and what it requires in the form of light, temperature, water and fertilizer for it to thrive. Since most bonsai are repotted at least once in their lives, that is a concern (how soon they can be moved, how soon after moving they can be fed and watered) but it is also an opportunity to start fresh with optimal conditions for your particular plant.
Type of Soil
One of the conditions that are completely in the bonsai gardener’s control is the type of soil in which they plant their tree or shrub. Bonsai soils can actually be an issue among gardeners. Many believe pre-mixed soils are the best, but they are expensive per pound and anyone with a large tree or numerous smaller ones could be apprehensive, especially with a new tree. Instead, it is often more economical to mix soil at home. Then the mix can be customized to the needs of each and every household conditions, or even every individual tree or plant. Soil needs a number of basic ingredients to produce healthy trees in general and some for bonsai in particular. With the shallow soil often used in the final potting for bonsai, it has to be exactly the right mix to allow the tree to extract the nutrients it needs for photosynthesis.
First, the soil must allow for good aeration. It is imperative that the roots have oxygen they need to breath and produce food. In a soil, this means the pieces or particles need to be large enough to let small gaps of air form amidst the particles as a whole. The soil must also have adequate drainage. Unnecessary water or moisture has to be able to go directly to the drain and out of the soil and pot. Too much water to prevent the aeration of the particles, allow mineral buildup (salt mainly) and could suffocate the roots. In addition, the soil must be able to keep enough water. Water retention by the soil is necessary to allow for the proper level of moisture going to the plant consistently between watering. Regular potting and top soil are very heavy and can retain too much water for too long. They can easily lead to sickly plants or root rot in most bonsai.
Tropical/Subtropical Mix and Conifer Mix
Bonsai soil is different for the soil depth and watering needs of this variety of trees. Bonsai soil mixes allow for fast and easy drainage, water retention and still let the roots get plenty of air and prevent the soil from compacting and gaining too much density. There are two main kinds of bonsai soil: tropical/subtropical mix and conifer mix. There are subcategories in both of these for some very particular plants and trees. But all require the drainage, water retention and aeration. Both are the more particle based, structured mix that allow air to come in and excess water to go out. Regardless of which soil mix works best for the gardener’s tree, it is essential that there be a hole for drainage in the pot and that a screen be added to the hole to stop the flow of soil out of the pot with the excess water.
Once a bonsai soil has these three main attributes, it can then be customized to the species of tree. Many have their own mixes, or the individual gardener can listen to the brand they have. Some that need more water will need soil with more retention while some are quite opposite and really just need the soil to let the water through as the gardener tries to figure out how much they need per plant.
Orchid Potting Mix
Orchids are one type of plant that need their own potting or soil mix. Often, orchids are planted in mixes made entirely of bark and charcoal with few other additives. Orchid soil mixes can be ideal for bonsai trees as well. The bark allows for excellent drainage and the size of the pieces is usually perfect for the right amount of aeration needed by bonsai trees. So many bonsai gardeners will use orchid soil/bark mixes for their trees or as a main ingredient in their own soil mixes. Beyond these basic elements, it is up to the bonsai gardener to select the right tree for their climate and light and then find exactly the right mix of soil ingredients that will keep their tree and garden healthy and thriving as they cultivate it into an aesthetic that reflects their own mindfulness and the tree’s beauty.