Fatsia japonica, also known as Japanese Aralia or False Castor Oil Plant, is an evergreen shrub popular for its bold, architectural foliage and tropical aesthetic. While generally low-maintenance, regular pruning is important for maintaining its health, managing its size, and enhancing its appearance.
Understanding Fatsia Japonica’s Growth
Fatsia japonica typically exhibits a multi-stemmed, rounded growth habit, reaching mature sizes of 6 to 10 feet in both height and spread in garden settings. In its native Japanese habitat, it can grow even taller, sometimes up to 16 feet. The plant is admired for its large, glossy, dark green leaves, which are palmately lobed with 7 to 9 deep divisions, often spanning 6 to 14 inches wide.
This shrub has a moderate to fast growth rate, typically adding 8 to 12 inches of height annually, depending on its growing conditions. Without intervention, its stems can become leggy and sparse, particularly at the base, leading to an overgrown or unkempt appearance.
When and Why to Prune Fatsia Japonica
The most opportune time to prune Fatsia japonica is mid-spring, just before its active growing season. Alternatively, prune from late winter to early spring, after the risk of severe frost has passed and winter damage is evident. This timing allows the plant to recover quickly and produce new, healthy growth. Avoid heavy pruning in late summer or fall, as fresh cuts may not heal adequately before cold weather, potentially stressing the plant.
Pruning promotes a compact, bushier form, preventing leggy or overly dense growth. Removing older, weaker stems improves air circulation, which helps deter pests and diseases. It also helps maintain desired size and shape, ensuring the shrub fits its allocated space.
How to Prune Fatsia Japonica
Tools and Preparation
Effective pruning requires the right tools for clean cuts.
- For smaller stems and leaves, use sharp bypass pruners.
- For thicker branches, loppers provide increased leverage.
- For very large or woody stems, a pruning saw may be necessary.
- Ensure all tools are clean and sharp to prevent disease spread.
- Wear gardening gloves to protect from sap and goggles for eye protection.
Basic Pruning Cuts
When making a cut, aim to prune just above a node or a bud. A node is where new growth emerges; cutting just above it encourages this. Make the cut at a 45-degree angle, approximately 1/4 to 1/2 inch above the chosen bud. This angled cut prevents water from pooling on the wound, reducing the risk of rot. Orient the cut so the bud faces the direction you want new growth to extend.
Pruning for Size and Shape
To manage Fatsia japonica’s size or maintain a specific shape, cut back branches selectively. This involves removing stems to reduce height and width while preserving its natural form. Thinning cuts, which remove entire branches back to their origin, are especially useful. This improves light penetration and air circulation, encouraging balanced growth. For a multi-stemmed tree form, remove lower branches to expose main stems and create an open structure.
Rejuvenation Pruning
For an older, overgrown, or leggy Fatsia japonica, rejuvenation pruning can revitalize the plant. This drastic approach involves cutting the plant back hard, sometimes by half its size or to the ground for very old stems. The goal is to encourage vigorous new growth from the base. For extensive rejuvenation, spread pruning over several seasons, removing about one-third of the oldest wood annually to avoid stressing the plant.
Removing Damaged or Dead Growth
Always begin by removing dead, diseased, or damaged branches. Cut these back hard, either to the main stem or base. Also remove any yellowing or unhealthy leaves, as they detract from the plant’s appearance. Prompt removal of compromised growth prevents problem spread and directs energy towards healthy development.
After Pruning Care
After pruning, water Fatsia japonica thoroughly. Maintain consistent soil moisture, ensuring the plant is not waterlogged. Monitor for new growth, which should emerge quickly, especially after spring pruning. A balanced fertilizer application in spring can encourage robust new foliage.