Article by Andrew Kozlowski
Bonsai Soil Selection
The soil you choose for your potted bonsai tree will provide it with nutrients, retain water, and play an important part in its overall health. You will need to find the right soil mix if you want your tree to thrive.
Both organic and inorganic soil mixes are available to bonsai tree growers. Organic soil mixes are comprised of dead leaves, peat, bark and other plant parts. Inorganic mixes are made from substances such as volcanic lava and clay. Soil mixes with a high inorganic content can prove better for bonsai health since they provide better drainage and more oxygen to the plant. Soils with a high organic content tend to retain too much water, and their particles break down over time, allowing less air to reach the plant. Good bonsai soil should have a mix of different sized particles, such as grit, sand, and peat, and hold enough water to hydrate the plant between each watering, while allowing for appropriate drainage.
Special inorganic soils for bonsai include Akadama, a porous Japanese baked clay that, mixed with sand and grit, becomes the perfect medium in which to grow pines and other bonsai. You can find this at a bonsai nursery. Seramis is another type of fired clay that is easier to find and cheaper than Akadama and can be mixed with peat or bark. It promotes root growth and is stronger than Japanese clay.
Different species require different water, nutrients, and soil. Coniferous bonsai such as junipers and pines need less moisture, so they need a soil that retains less water. Tropical flowering plants, conversely, will often need more water, and therefore require a soil that retains water more effectively. Check with an expert at a bonsai nursery for a soil recommendation for your particular bonsai species.
Bonsai Pot Selection
The pot in which you place your bonsai should complement the shape and style of the tree. The size, color, and design of the container should all be taken into consideration. While you can train your bonsai in an informal tray or box, a fully shaped tree should be displayed in a formal bonsai container. These are usually ceramic stoneware that can be glazed or unglazed in a variety of colors and sizes. All bonsai pots should have drainage holes in the bottom to let out excess water.
Your bonsai pot should be resistant to both heat and cold. Most stoneware pots are fired to withstand temperature changes. If you know your bonsai will be located outdoors in an extreme climate, it’s best to select an unglazed pot. If your bonsai will reside exclusively indoors, you can use a porcelain pot, which can lend an elegant look to a flowering tree.
Color is an important consideration. Most bonsai gardeners choose unglazed, rustic containers in earth tones for outdoor bonsai such as evergreens and pines, while flowering or fruit-bearing trees such as brush cherries can be accented by a more colorful, glazed pot. Many like the subtle colors of Japanese mud pots or Chinese red clay pots for trees with green foliage, and blue, green, and white pots for tropical bonsai.
The shape and depth of the container should match the style of the bonsai. Whether oval, round, or rectangular, the pot should be deep enough to accommodate slanted trunks or branches, or cascade-style limbs that dip below the container’s edge.
About the Author
Andrew Kozlowski is a naturalist, amateur botanist, and author of articles and books on topics ranging from plant care and gardening to home downsizing. For more than 20 years Andrew has managed environmental programs in the U.S., Europe, Africa, and Latin America. He resides in San Francisco.