Hardy rubber tree (Eucommia ulmoides) is a rubber tree native to China that may be extinct in the wild. It is commonly cultivated as a shade tree, valued for its glossy leaves and low susceptibility to disease or insect-related problems. This particular species is not good for commercial rubber production, but has a valued place in traditional Chinese culture.
I. Appearance and Characteristics
Eucommia ulmoides is a species of small tree native to China. It belongs to the monotypic family Eucommiaceae.
E. ulmoides is the sole living species of the genus Eucommia. Eucommia is the only genus of the family Eucommiaceae, and was formerly considered to be a separate order, the Eucommiales. It is also sometimes known as “gutta-percha tree” or “Chinese rubber tree”, but is not related to either the true gutta-percha tree of southeastern Asia, nor to the South American rubber tree.
Eucommia ulmoides grows to about 15 m tall. The leaves are deciduous, arranged alternately, simple ovate with an acuminate tip, 8–16 cm long, and with a serrated margin. If a leaf is torn across, strands of latex exuded from the leaf veins solidify into rubber and hold the two parts of the leaf together. It flowers from March to May. The flowers are inconspicuous, small and greenish; the fruit, June to November, is a winged samara with one seed, very similar to an elm samara in appearance, 2–3 cm long and 1–2 cm broad.
This tree is also occasionally planted in botanical gardens and other gardens in Europe, North America and elsewhere, being of interest as the only cold-tolerant (to at least -30 °C) rubber-producing tree. Fossils of other Eucommia species have been found in 10- to 35-million-year-old brown coal deposits in central Europe and widely in North America, indicating that the genus had a much wider range in the past.
II. How to Grow and Care
Hardy rubber tree is a robust plant that generally requires minimal maintenance, making it an easy-care species suitable for a variety of gardeners. A key special care point for hardy rubber tree is that it thrives in well-draining soil with consistent moisture, though it is tolerant of drought once established. Adequate sun exposure is critical, as hardy rubber tree prefers full sun to partial shade for optimal growth.
Sunlight
Hardy rubber tree thrives in full sun conditions where it can receive unfiltered sunlight for 6 or more hours per day. Its growth and health are optimal when exposed to this intensity of light, as it influences photosynthesis rates, and thus, energy production for growth and development. While hardy rubber tree is tolerant of partial sun and can adapt by adjusting leaf orientation to maximize light capture, extended periods of low-light exposure may result in leggy growth and a reduction in vigor.
Outdoors, hardy rubber tree should be planted in locations where it can receive ample sunlight, away from larger trees that might create dense shade. Adequate light exposure enables hardy rubber tree to maintain its robust, rubber-producing capabilities and ensures a healthy, resilient specimen.
Watering
Originating from central China, hardy rubber tree is well-adapted to withstand periods of drought due to its native environment fluctuating water availability. This species exhibits a robust tolerance for dry spells, maintaining equilibrium by storing water efficiently within its structure. Watering should be done once every two weeks to mimic the natural hydration cycle it experiences in the wild. As an outdoor plant often subjected to varying weather patterns, hardy rubber tree has evolved to optimize its water uptake during the rainy season, ensuring sustained growth and resilience throughout drier periods.
Fertilizing
For hardy rubber tree, apply balanced nutrition fertilizer in spring and summer to support vigorous growth. High nitrogen fertilizers can be used early in the growing season to boost leaf development. Fertilize monthly with half-strength doses, avoiding over-fertilization which may damage the root system. In autumn, reduce frequency as hardy rubber tree enters dormancy. Ensure even distribution around the drip line, integrating into the soil for optimal uptake. Novice gardeners should start with lighter applications, observing hardy rubber tree’s response. Experienced enthusiasts might tailor applications, considering soil tests and hardy rubber tree’s growth stage. Always water hardy rubber tree after applying fertilizer to help absorption.
Propagation
Hardy rubber tree, a deciduous tree valued for its medicinal bark and resilient nature, propagates effectively through sowing. For successful germination, the seeds require a well-draining medium and consistent moisture. It’s crucial to sow them at a shallow depth, as they need ample light to initiate growth. Optimizing the soil’s fertility with organic matter enhances the chances of robust seedling development. Once sprouted, gentle handling of seedlings is important to prevent damage to their tender roots during transplantation.
Transplanting
The perfect period for rehoming hardy rubber tree is the vernal season, providing a gentle start for root establishment. Select a sun-kissed, well-draining locale to encourage robust growth. Gentle handling promotes seamless transition.
III. Uses and Benefits
It is one of the 50 fundamental herbs used in Chinese herbology, where it is called dùzhòng (Chinese: 杜仲). Because of the low production and high demand for natural rubber in China, a unique process has been developed to manufacture elastic materials with Eucommia ulmoides gum (EUG) as substitutes for natural rubber products. Unlike the latex used to produce natural rubber, the EUG is the polymer trans-1,4-polyisoprene. Thus materials made from EUG may demonstrate characteristics other than those of natural rubber, such as higher elasticity, lower thermoplastic temperature,..
