Robinia pseudoacacia, commonly known as the black locust, is native to North America and was first introduced to Europe in 1601. It was later brought to China after 1877. Over time, it has gained widespread popularity due to its strong adaptability, fast growth, ease of propagation, and versatile uses. Today, it is found throughout northern, northwestern, and southeastern China, stretching from Tieling in Liaoning to the Yangtze River region. The tree thrives in dry, cool climates and is highly drought-tolerant. It can grow in a variety of soils, including calcareous, acidic, neutral, and slightly saline soils, although it performs best in well-drained, sandy soil that is rich and moist.
One of the remarkable features of Robinia pseudoacacia is its ability to form symbiotic relationships with rhizobia, which help fix atmospheric nitrogen, enriching the soil and supporting its own growth. This makes it an ideal species for ecological restoration projects such as soil and water conservation forests, windbreaks, and firewood plantations. In addition, its ornamental value has increasingly attracted attention, especially in areas with poor soil conditions or high levels of environmental pollution, where it has become a key species in urban landscaping.
The tree grows best when the average annual temperature ranges between 8°C and 14°C, and the annual rainfall is between 500 and 900 mm. If the average temperature exceeds 15°C or the rainfall surpasses 900 mm, the growth period shortens, and the trunk may become curved. When temperatures drop below 7°C, the tree may experience dry shoots, and at temperatures below 5°C, it tends to grow in a shrub-like form. Robinia pseudoacacia also exhibits strong resistance to air pollutants such as hydrogen fluoride, chlorine, nitric oxide, nitrogen dioxide, ozone, and sulfur dioxide, making it a resilient choice for urban environments.
Internationally, there are many ornamental varieties of Robinia pseudoacacia. For example, 'Bessouiana' features a tall, straight trunk with yellowish-white flowers, while 'Frisia' is known for its golden leaves that remain vibrant all year. 'Tortuosa' has twisted branches, and 'Pyramidalis' forms a columnar shape with a cylindrical crown. 'Umbraculifera' has a rounded, umbrella-like canopy, and 'Stricta' is recognized for its tortoiseshell-like bark. 'Lobularia' (also called 'Unifolia') has smaller leaves compared to the standard variety.
In China, several ornamental types have been developed, such as 'Decaisneana', which has purple flowers and is cultivated in cities like Nanjing and Beijing. 'Spiniculite' (R. pseudoacacia var. inermis) has an open crown and is used for street trees. 'R. pseudoacacia var. microphylla' has small leaves and is grown in Zaozhuang, Shandong. Other local varieties include 'Upright', which has a straight trunk, and 'Yellow Leaf', known for its long-lasting yellow-green foliage.
For ornamental use, various techniques are employed, such as grafting, to create specific shapes. The 'Crown' type is often used in European cities, with a neat spherical shape suitable for streets and public spaces. The 'Golden Leaf' variety adds color to landscapes, while 'Quzhi' (Twisted Branch) offers a more rustic, aged appearance, ideal for historic sites or bonsai-style planting. The 'Red Flower' variety, with its vivid red blossoms, is popular as a flowering shrub or garden tree.
The 'Sharp Stick' variety, similar to the 'Column' type found abroad, has a tall, slender trunk and is often planted near buildings or along roadsides. It is unique in that it can flower twice a year—once in May and again in July—with striking red blooms.
Due to its rich intraspecific variation, Robinia pseudoacacia offers great potential for breeding ornamental varieties. Its diverse traits, including flower color, leaf color, branch structure, and bark texture, can be preserved through cloning. With its strong adaptability and resilience, this tree has broad application potential, particularly in challenging environments where other species may struggle. The development of ornamental varieties has already advanced significantly in many countries, and with continued research and cultivation, its role in urban and ecological landscapes will only continue to grow.
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