Trident maple (Acer buergerianum), or three-toothed maple, originated from Eastern China, Japan, and Korea.
The trident maple is a very desirable tree for bonsai because it is hardy, with strong roots, a trunk, and branches that thicken quickly. It has lovely exfoliating bark and lush, beautiful leaves as the tree matures. Fall colors can be yellow, orange, and red.
Collecting
Trident maple is a common landscaping tree and can be found in nurseries. They are usually seed-grown and therefore may have variations in characteristics. Choose a tree with the features that appeal to you to make into a bonsai.
For example, seedlings from the Taiwanese Trident maple (Acer buergerianum formosanum) have slightly thicker leaves and are less susceptible to leaf burn in hot, dry weather.
Environment
Trident maple grows vigorously in full sun and can also be kept in partial shade. Leaves may burn in hot and dry weather, but not as easily as those of Japanese maple trees (Acer palmatum).
It is a good practice to rotate your bonsai from time to time to ensure even exposure and even growth.
Styling
Trident maple is a vigorous grower. Its trunk and branches thicken quickly, and its leaves reduce in size with ramification. They are most often made into formal and informal upright bonsai and forest groves, but these attributes allow the bonsai hobbyist to style them in any form.
Trimming
Leaves can be trimmed on healthy trees after the first flush of spring growth has hardened off. This encourages light and air into the interior of the tree's branches to promote growth.
Using snippers, trim off the branchlets to the right length above a bud. Given that buds are paired on opposite sides of the branch, you can cut off one of the buds to encourage the branch to grow in the desired direction. This is an aspect of the clip-and-grow method.
It is necessary to strip the leaves when growth obscures where to clip. This is called defoliating, which can be partial or complete late in the season. Doing so encourages buds to form branches, increases ramification, and results in leaves emerging with a uniform look.
Some believe that defoliating should only be done on healthy trees. While this may be true, it certainly slows down growth because there is less photosynthesis.
Pruning
Cut off long water shoots—straight, heavy shoots—because they are likely outside your design parameters.
Cut to simulate branches breaking off naturally to create an aged look. Sometimes it is desirable to leave a stub (jin) to achieve this effect.
Some recommend the use of sealant to protect cuts. This may not be necessary, as trident wood does not decay readily, and cuts close up quickly.
Once your tree has taken on its fall color, the leaves are no longer photosynthesizing, and it is safe to prune heavy branches without worrying about sap “bleeding.”
Wiring
Like most deciduous trees, wiring can often be avoided by judicious trimming at the appropriate time. Ensure your wiring is sufficient to hold the branch but loose enough to accommodate rapid branch growth in the spring. Guy wires can be used to simulate naturally drooping branches.
Pot and Repotting
Deciduous trees with fall color look good in complementary colored pots: blue, cream, yellow, etc. Choose a pot style that complements the tree's style.
The BH standard soil mix should work fine for trident maple trees. Consider using the BH proprietary pot, which essentially has a soaking basin built in to keep the root ball moist.
The best time to repot your trident maple is from late fall to spring in mild climates, and in early spring to avoid roots freezing. Look for leaf buds beginning to "shine" and expand slightly.
Watering
The frequency and amount of water depend on your soil, sunlight exposure, and weather conditions. Choose a soil mix that maintains moisture but provides pores for air to reach roots. Count on watering at least once a day. Water when the surface of the soil is dry, and water thoroughly. Avoid watering the leaves to prevent water spots and fungal infections in humid areas.
Fertilizing
Some bonsai masters recommend starting fertilizing with a fertilizer with low N-P-K numbers after the leaves have hardened off in the spring. Apply fertilizer every two weeks until summer dormancy. Then use a 0-10-10 fertilizer until the tree loses its leaves. Others believe any fertilizer in modest amounts would work fine for tridents, including 15-15-15 slow-release lawn fertilizer.
Pest Management
Like most trees, trident maple may be susceptible to mildew in humid climates. Spray with a solution of 2 teaspoons baking soda per gallon of water. Follow up with another spray in a week, and, if necessary, once more. Keeping the area around your bonsai clean is a first line of defense.
Sucking pests like aphids can be dealt with using a sharp spray of water or malathion. Apply bait like Amdro to control ants, and BioAdvanced 3-in-1 Rose and Flower Granules to address various issues.
Propagation
Collect seeds in early fall and remove their "wings." Wash the seeds with a mild solution of fungicide and let them dry. Store in an opaque container in moist paper towels or sphagnum moss in the fridge until ready to plant.
Plant seeds in the spring in a pot of planting mix covered with 1/2 inch of peat moss. Place seeds on top of the peat moss, then cover with a sprinkle of fine shale or lava rock so they won't float away when you water.
Trident maple cuttings can be readily rooted from early spring until early summer. Air layering is done from early spring onward, as it is easier to strip the bark during the active growing season.
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