Bean tree (Laburnum × watereri)

Overview

The Laburnum × watereri, commonly known as the Bean tree, is a prized garden hybrid celebrated for its dramatic, pendulous displays of brilliant yellow, wisteria-like flowers in late spring. This specimen creates a spectacular focal point, bringing unparalleled color to the transitioning seasons. Gardeners value Laburnum × watereri for its relatively low maintenance needs once established, provided it is sited correctly.

As a cross between L. Alpinum and L. Anagyroides, this hybrid inherits desirable traits while often producing a slightly sparser, yet still profuse, bloom display. It matures into a medium-sized tree or large shrub, offering structure and seasonal interest. While beautiful, remember that all parts of the Bean tree are highly poisonous, requiring careful placement away from accessible areas.

The best performance for this beautiful flowering tree is typically seen in regions with moderate summers and winters, such as the Pacific Northwest. Proper siting is crucial for ensuring the magnificent bloom show of the Laburnum × watereri year after year.

Fast Facts

• Plant Family: Fabaceae
• Plant Type: Tree
• Native Range: Garden origin
• Hardiness Zones: USDA Zones 5-7
• Size at Maturity:
  • Height: 15-30 ft
  • Spread: 15-30 ft
• Bloom Time: May to June
• Bloom Description: Yellow
• Sun Exposure: Full sun to part shade
• Water Needs: Medium
• Maintenance Level: Low

How to Grow

Planting the Bean tree should ideally occur in the spring or fall, allowing the roots time to establish before stressful weather peaks. This magnificent specimen thrives in organically rich, medium moisture, well-drained soils. While it performs best in full sun, providing afternoon shade in extremely hot summer climates, such as those resembling the St. Louis area, can prevent scorching and stress.

Watering requirements for Laburnum × watereri are medium; maintain consistently moist (but never waterlogged) soil, especially while the plant is young. Established plants tolerate some dryness but perform best with regular deep watering during dry spells. Maintenance is generally quite low; however, if you train the Laburnum × watereri as a small tree, promptly remove any root suckers that emerge to maintain the desired structure.

Be aware that the seedpods, which follow the spectacular yellow flowers, are not ornamental and consume plant energy; consider removing them promptly, especially since all parts are quite poisonous. Avoid planting this tree south of USDA Zone 7, as it performs poorly in high heat and humidity characteristic of the deep South. In cooler zones, site the Laburnum × watereri in a protected area to guard against potential damage from severe sub-zero winter temperatures.

Landscape Uses

The Laburnum × watereri functions beautifully as a small specimen tree, instantly drawing the eye with its cascading floral curtains in May and June. Beyond its use as a standalone feature, the Bean tree is highly versatile; it can be grown successfully as a large shrub or formally trained against structures. Consider utilizing its strong vertical lines to train it over arbors, pergolas, or even espaliers, transforming utilitarian structures into vibrant, living architecture.

This plant also serves excellently as a textural background element in mixed borders where its summer green leaves can serve as a solid backdrop contrasting with other flowering plants. When planning companions, choose plants that appreciate similar moderate soil and moisture conditions, offering contrasting flower shapes or colors to complement the yellow racemes of the Bean tree without competing for light.

Standout Features

Flower Qualities

• Showy

Noteworthy Characteristics

Laburnum × watereri, commonly called golden chain tree, is noted for its pendulous axillary racemes of yellow, wisteria-like flowers that bloom in spring. This hybrid is a cross between L. Alpinum and L. Anagyroides. It typically grows 25-30’ tall as a tree, and 15-20’ tall as a shrub. Trifoliate, clover-like, medium green leaves (to 3” long) produce little fall color.

Tolerances

Potential Problems

Twig blight represents an infrequent but potentially serious fungal disease that can affect the Laburnum × watereri. Lesser disease issues include canker and various leaf spots, which typically cause cosmetic damage rather than significant long-term harm. Vigilance against common pests like aphids and mealybugs is also warranted; regular inspections, especially of new growth, can catch infestations early. Good air circulation achieved through proper spacing and pruning can help mitigate fungal issues.

Frequently Asked Questions

What hardiness zones is Bean tree suitable for?

The Laburnum × watereri is hardy and thrives in USDA Zones 5 through 7.

How large does Bean tree grow?

This hybrid typically matures to a height between 15 and 30 feet, with a similar spread ranging from 15 to 30 feet wide.

When does Bean tree bloom?

The spectacular floral display of the Bean tree occurs from May through June, presenting bright yellow flowers.

What sun exposure does Bean tree need?

Laburnum × watereri prefers full sun exposure but appreciates receiving some part afternoon shade, especially in the hottest regions.

Conclusion

The Laburnum × watereri, or Bean tree, offers unmatched spring drama with its waterfall production of vibrant yellow blooms, making it a low-maintenance standout for temperate gardens. Ensure your location provides well-drained soil and appropriate hardiness zone compatibility before planting this showy specimen. Plan your planting in the spring or fall to give your new specimen the best start.

Design Ideas

Companion Planting

Selecting appropriate partners enhances the appeal of the Bean tree throughout the growing season. Since Laburnum × watereri blooms early, consider pairing it with summer-blooming perennials that offer contrasting foliage textures, such as hostas or ferns, especially in locations where afternoon shade is provided. Plants that require consistent, medium moisture levels are ideal companions. Avoid planting near bulbs and herbs that might be disturbed by the management of root suckers common to this family.

Seasonal Care Calendar

Focus seasonal efforts around maximizing bloom quality and managing toxicity. In early spring, before significant growth, monitor for potential fungal issues like blight and apply treatments if necessary. After flowering concludes in June, this is the opportune time to deadhead or remove seedpods if you choose to do so, directing the plant’s energy toward root and foliage development rather than seed production. In late fall, water deeply if the season was dry as the tree enters dormancy.