Japanese spikenard (Aralia cordata 'Sun King')

Overview

Aralia cordata ‘Sun King’, commonly known as Japanese spikenard, offers spectacular color in the shade, making it a highly valued specimen for dim garden corners. This cultivar is cherished for its large, rounded clump of vibrant golden-yellow compound leaves that light up shady landscapes throughout the growing season. As a fast-growing, rhizomatous perennial, Aralia cordata ‘Sun King’ establishes quickly, providing substantial architectural interest from spring until frost.

This herbaceous perennial typically reaches heights and spreads between three to six feet wide in a single season. Alongside its impressive foliage, it produces airy spikes of small white flowers in late summer, followed by attractive berries loved by birds. With low maintenance requirements, Aralia cordata ‘Sun King’ is perfect for gardeners seeking bold impact without constant attention.

The native environment of Japanese spikenard informs its success in gardens: it thrives best in protected, dappled light settings where its foliage is shielded from harsh afternoon sun and strong winds. Its ornamental value and toughness secure its place as a superb structural plant in woodland and shade gardens.

Fast Facts

• Plant Family: Araliaceae
• Plant Type: Herbaceous perennial
• Hardiness Zones: USDA Zones 4-8
• Size at Maturity:
  • Height: 3-6 ft
  • Spread: 3-6 ft
• Bloom Time: July to September
• Bloom Description: White
• Sun Exposure: Part shade
• Water Needs: Medium
• Maintenance Level: Low

How to Grow

The best time to establish Japanese spikenard is typically in the spring after the last threat of frost has passed, or in early fall. Select a location that offers part shade to ensure the best golden foliage color without scorching the leaves. Aralia cordata ‘Sun King’ demands fertile, humusy soil that maintains consistent moisture but remains well-drained.

Watering requirements for this plant are medium; ensure the soil does not dry out completely, especially during hot summer spells. Fertilization generally isn’t necessary if the soil is rich, but a light layer of compost applied annually can boost vigor. Pruning is minimal, mainly involving cutting back the entire clump to the ground in late winter or early spring before new growth emerges.

A crucial care consideration is siting: plant Aralia cordata ‘Sun King’ where it is somewhat protected from strong winds, which can shred its large compound leaves. If conditions are ideal, notice that these plants are somewhat easy to naturalize, as they readily self-sow where the dark berries drop.

Landscape Uses

The primary suggested use for Aralia cordata ‘Sun King’ is to naturalize in woodland or partially shaded settings, allowing it to form impressive, self-sustaining colonies over time. Its bold texture and bright golden hue contrast beautifully against darker green foliage plants commonly found in shady borders.

Utilize this plant toward the rear of shaded borders where its height (up to 6 feet) can anchor the design. In larger gardens, mass plantings of Japanese spikenard create a stunning, continuous swath of warm color that brightens deep shade areas beautifully. It works wonderfully near paths or water features where its size can be fully appreciated.

Standout Features

Flower Qualities

• Showy

Noteworthy Characteristics

Aralia cordata, commonly known as Japanese spikenard, mountain asparagus or udo, is a thornless, rhizomatous, herbaceous perennial that typically grows somewhat rapidly to 3-6’ tall and as wide in a single season. It is native to shady parts of forested areas and grassy slopes in Japan, Korea and east-central to southern China. Compound leaves (to 3’ long) are 2-3 pinnate with 3-7 coarse, finely toothed, cordate-based, ovate leaflets (each to 6” long) per pinna. Inflorescence consists of white flowers in umbels arranged in large terminal and axillary spike-like panicles (to 1 1/2’ long). Flowers bloom from late summer to early fall (late July -September). Young shoots of this plant are considered a culinary delicacy in Japan (taste resembling that of asparagus) where they are cultivated in underground tunnels. White fleshy roots (elongate cylindric rhizomes) are eaten as one would consume a parsnip. Young udo leaves may be eaten as a vegetable.Genus name comes from the Latinization of the old French-Canadian name of aralie.Specific epithet from Latin means heart-shaped in reference to the plant leaflets.‘Sun King’ is a golden-leaved cultivar that features a large rounded clump of golden yellow compound leaves which is topped in summer by 2’ tall spikes of tiny white flowers. Deep reddish-purple to purplish-black inedible berries ripen in fall. Birds love the berries. Foliage retains good yellow color throughout summer unless grown in too much shade. This cultivar was introduced into the U.S. By Barry Yinger who reportedly found it in a department store nursery in Japan.

Tolerances

• Deer

Potential Problems

Aralia cordata ‘Sun King’ is generally robust and suffers from no serious insect or disease problems when sited correctly. Gardeners should remain observant for common pests that occasionally seek out perennials, including aphids, mealybugs, and spider mites. Slugs and snails can also pose a threat, particularly when the new shoots emerge in spring.

Fungal issues are usually cosmetic; leaf spot may appear, especially if air circulation is poor or if the foliage remains wet for extended periods. Good cultural practices—like ensuring excellent drainage and managing nearby weeds to improve airflow—are usually sufficient to keep these minor issues under control.

Frequently Asked Questions

What hardiness zones is Japanese spikenard suitable for?

Aralia cordata ‘Sun King’ performs reliably in USDA Hardiness Zones 4 through 8.

How large does Aralia cordata ‘Sun King’ grow?

This herbaceous perennial generally reaches a mature height between 3 to 6 feet tall, with a comparable spread of 3 to 6 feet wide.

What sun exposure does Japanese spikenard need?

This plant performs best when provided with part shade conditions; too much intense, direct sun can scorch the brilliant golden foliage of the ‘Sun King’ cultivar.

When does Aralia cordata ‘Sun King’ bloom?

Flowering occurs from mid-to-late summer, specifically between July and September, producing small white blooms.

Conclusion

The combination of vibrant, season-long golden foliage and low maintenance makes Aralia cordata ‘Sun King’ an essential structural plant for shaded garden designs. The visual power of this Japanese spikenard vastly outweighs its minimal cultural demands. Before planting, verify that your intended site provides the necessary part shade and moist, well-drained soil to ensure the best performance from your Aralia cordata ‘Sun King’.

Wildlife Benefits

The late-season flowers of Aralia cordata ‘Sun King’ provide nectar and pollen when many spring bloomers are finished, supporting late-season pollinators. While the flowers are attractive, it is the subsequent fruit that offers a significant boost to local wildlife.

Following bloom time, the plant produces masses of deep reddish-purple to purplish-black berries in the fall. These berries are highly attractive to many species of songbirds, providing a crucial late-season food source before migration or winter dormancy. Planting Aralia cordata ‘Sun King’ near shelter areas can encourage birds to frequent your garden space.

Companion Planting

When selecting companions for Aralia cordata ‘Sun King’, focus on plants that share its love for part shade and medium moisture levels. Dark green, contrasting foliage creates the strongest visual effect against the bright gold leaves. Consider using large hostas with deep blue or variegated leaves as groundcover beneath the fountain-like sprays of the Japanese spikenard.

For vertical contrast, pair the broad leaves of Aralia cordata ‘Sun King’ with taller, slender vertical accents like ornamental grasses adapted to shade, or tall white-flowering Astilbe (if moisture is high). The goal is to complement the coarse texture and bright color of the Aralia while ensuring all plants thrive in similar light conditions.