The Hawaiian Umbrella tree, a great beginner bonsai
The hawaiian umbrella tree, dwarf schefflera arboricola, in nature grows as a small evergreen shrub. As such, it can be easily trained into bonsai form. The roots respond well to pruning and it is not as picky about watering as many other bonsai trees. As it is an evergreen, it has dark green leaves year round that fan out into an umbrella form which makes it ideal for creating a bonsai style needing a dense canopy. Often times they are used in forest plantings.
What makes the Schefflera Arboricola a good bonsai for beginners?
The hawaiian umbrella tree has many characteristics that make it an excellent choice for beginners. First, it can grow well in lower lighting conditions. Most beginners try to keep their trees indoors. This is one of the trees that actually do well in indoor conditions. They do best in USDA zones 9-11 so most people who live north of Florida, Texas, and California keep them indoors year round without any issues. Of course, they will do their best if the indoor location is exposed to indirect lighting from an east or west facing window or in rooms with fluorescent lighting on for long portions of the day.
Second, schefflera are not very picky about watering conditions. Incorrect watering is how most beginners end up killing their bonsai trees. These trees are pretty forgiving as long as one does not allow the soil to dry out completely. It is good about letting the owner know if it is being overwatered or underwatered. The hawaiian umbrella's leaves will turn black if it is being overwatered or start to curl at the ends if it is being underwatered.
Additionally, they do appreciate high humidity conditions. Indoor conditions tend to be very dry. To increase the humidity around the bonsai it is recommended you place the pot on top of a humidity tray filled with pebbles and water. The evaporating water humidifies the surrounding air. Avoid abnormally dry areas near heaters, furnaces, and fireplaces.
Last, this tree is not picky about the soil you pot it in. Any free draining soil will work fine with this tree whereas with other bonsai species they can be very picky. They are tolerant of clay, sand, and loamy soils. Schefflera do prefer a slightly alkaline soil so adding a little lime in the soil mix can adjust the pH more towards alkaline if so desired.
It can be difficult to train this tree into any form other than something with a broad crown similar to a banyan fig. They are not ideal for training into traditional Japanese forms, but they can be made into informal uprights. Most often they are trained into multiple trunk or forest groups. One of their interesting characteristics are their aerial banyan roots that they send down from lower branches. These aerial roots are great when trying root over rock styles. To encourage branching one can pinch stems back. Also, ideally try to repot younger trees every one to two years in the spring. You can aggressively root prune if necessary at that time.
Watering your Hawaiian Umbrella bonsai
As mentioned, never let the soil dry out completely. Additionally, never water by a schedule. Instead, water when you notice the soil beginning to dry out. When it is time to water, thoroughly soak the soil by watering from above until the water begins to come out of the pot's drain holes. You may notice the tree will need less water in the winter months.
Final Indoor Considerations
The hawaiian umbrella tree is very resistant to pests and diseases outdoors, but one needs to be on the lookout for pests which it has no predators against indoors if grown there. Be watchful for scale, spider mites, and mealy bugs when this tree is grown indoors. Additionally, all parts of this tree are poisonous so keep this tree away from children and pets and try not to get sap on your skin.