Siberian elm is a deciduous plant recently introduced to Southern Europe from Asia. The plant rapidly resprouts from its roots and is considered invasive. It is planted to break winds and control soil erosion. The plant is quite hardy and can grow in soils that are saline or polluted.
I. Appearance and Characteristics
Ulmus pumila, the Siberian elm, is a tree native to Asia. It is also known as the Asiatic elm and dwarf elm, but sometimes miscalled the ‘Chinese elm’ (Ulmus parvifolia). U. pumila has been widely cultivated throughout Asia, North America, Argentina, and southern Europe, becoming naturalized in many places, notably across much of the United States.
The species was described by Peter Simon Pallas in the 18th century from specimens from Transbaikal.
The Siberian elm is usually a small to medium-sized, often bushy, deciduous tree growing to 25 metres (82 feet) tall, the diameter at breast height to 1 m (3 ft 3 in). The bark is dark gray, irregularly longitudinally fissured. The branchlets are yellowish gray, glabrous or pubescent, unwinged and without a corky layer, with scattered lenticels. The winter buds dark brown to red-brown, globose to ovoid. The petiole is 4–10 millimetres (1⁄4–1⁄2 inch), pubescent, the leaf blade elliptic-ovate to elliptic-lanceolate, 2–8 by 1.2–3.5 centimetres (3⁄4 in–3+1⁄8 in × 1⁄2 in–1+3⁄8 in), the colour changing from dark green to yellow in autumn. The perfect, apetalous wind-pollinated flowers bloom for one week in early spring, before the leaves emerge, in tight fascicles (bundles) on the last year’s branchlets. Flowers emerging in early February are often damaged by frost (causing the species to be dropped from the Dutch elm breeding programme). Each flower is about 3 mm (1⁄8 in) across and has a green calyx with 4–5 lobes, 4–8 stamens with brownish-red anthers, and a green pistil with a two-lobed style. Unlike most elms, the Siberian elm is able to self-pollinate successfully.
The wind-dispersed samarae are whitish tan, orbicular to rarely broadly ovate or elliptical, 1 cm–2 cm × 1 cm–1.5 cm (3⁄8 in–3⁄4 in × 3⁄8 in–5⁄8 in), glabrous except for pubescence on stigmatic surface; the stalk 1–2 mm (5⁄128–5⁄64 in), the perianth persistent. The seed is at the center of the samara or occasionally slightly toward apex but not reaching the apical notch. Flowering and fruiting occur March to May. Ploidy: 2n = 28. The tree also suckers readily from its roots.
The tree is short-lived in temperate climates, rarely reaching more than 60 years of age, but in its native environment may live to between 100 and 150 years. A giant specimen, 45 kilometers (28 miles) southeast of Khanbogt in the south Gobi, with a girth of 5.55 m (18 ft 3 in) in 2009, may exceed 250 years (based on average annual ring widths of other U. pumila in the area).
II. How to Grow and Care
Sunlight
Siberian elm’s optimal light conditions consist of full sunlight exposure that fuels its vigorous growth and promotes robust health. Its high adaptability allows it to also thrive in partial sun, though deviations from full sun may lead to reduced growth vigor and potential density variations in foliage. It exhibits adaptability through leaf positioning to maximize light absorption. Outdoors, siberian elm should be planted in open spaces where daylight is abundant. However, under less-than-ideal conditions, siberian elm has the resilience to acclimate and still maintain health, albeit with potential impacts on its growth rate and form.
Temperature
Plants of Genus Ulmus are mainly native to the temperate zone of the northern hemisphere. These trees are known for their adaptability – they enjoy adequate sunshine, but are also tolerant to cold and drought, with a developed root system that provides resistance to strong winds and soil erosion. The trees have a long lifespan and are usually fast growers, with strong vitality.
Watering
Originating from semi-arid regions, siberian elm has adapted to survive with less frequent hydration, displaying moderate drought tolerance. In its natural habitat, it experiences periods of low precipitation, which informs its water habits. Watering for siberian elm should be adjusted to once every 1-2 weeks, aligning with its ability to withstand drier conditions. Typically grown outdoors due to its size and growth habit, siberian elm thrives in well-draining soil that mimics the dry steppe climate of its origin.
Soil
Siberian elm can tolerate a variety of different soil types and pH values, but good drainage is a must. Fertile sandy loam is best suited to the tree’s growth, and this can be mixed with garden soil, leaf mold and river sand at a ratio of 1:1:1 as cultivation soil.
Fertilizing
To boost the robust growth of siberian elm, utilize balanced nutrition fertilizers in spring and fall, switching to high-nitrogen formulations during active growth periods to support foliage development. Opt for a moderate application frequency, every 4-6 weeks, adjusting the quantity per product instructions while respecting the plant’s size and growth stage. Fertilization enhances vigor, leaf quality, and resilience. Less is more; over-fertilization risks root burn and growth imbalance. Seasonal changes inform adjustments: less in dormant winter, more in energetic spring/summer.
Pruning
Prune siberian elm in the late winter to thin its branches and remove any that are diseased. This is also a good time to prune for tree shape. In the spring, once the branch buds sprout, you will need to remove any excessive lateral buds. Select the buds from the parts needed for cultivation to maintain the tree’s shape, as this will reduce unnecessary nutrition consumption.
Propagation
Siberian elm has multiple propagation methods including hardwood cuttings, layering (air), and sowing seeds in Autumn and Winter. Propagation difficulty varies, but successful propagation can be identified by new growth and root development. Key tips include ensuring proper soil moisture and temperature.
Transplanting
The perfect time for transplanting siberian elm is during late spring to midsummer, as it allows ample warm weather for establishment. Opt for a location with full sun, well-draining soil, and space for growth. Remember: Siberian elm thrives when given room to expand.
Repotting
Repot siberian elm every 2-3 years, ideally in early spring before the growth phase. As a large, fast-growing tree, ensure a spacious container to accommodate its root system. Use a sturdy pot with ample drainage holes to prevent waterlogging. Post-repotting, water well and place in an area with full sun to partial shade, keeping soil consistently moist for healthy recovery and growth.
Pests and Diseases
The tree has considerable variability in resistance to Dutch elm disease; for example, trees from north-western and north-eastern China exhibit significantly higher tolerance than those from central and southern China. Moreover, it is highly susceptible to damage from many insects and parasites, including the elm leaf beetle Xanthogaleruca luteola, the Asian ‘zigzag’ sawfly Aproceros leucopoda, Elm Yellows, powdery mildew, cankers, aphids, leaf spot and, in the Netherlands, coral spot fungus Nectria cinnabarina. U. pumila is the most resistant of all the elms to verticillium wilt.
III. Uses and Benefits
- Ornamental uses
Gardeners grow the siberian elm for its landscaping value in promoting erosion control along slopes and banks. A very large tree, the siberian elm can also be kept as a specimen plant. It is prized for its resistance to poor soil, pollution, and drought and is most often used in woodland and cottage gardens. The Siberian elm does well when accompanied by red elm and will readily hybridize.
- Culinary uses
The unripe seeds have long been eaten by the peoples of Manchuria, and during the Great Chinese Famine they also became one of the most important foodstuffs in the Harbin region. The leaves were also gathered, to the detriment of the trees, prompting a prohibition order by the authorities, which was largely ignored. The leaves eaten raw are not very palatable, but stewed and prepared with Kaoliang or Foxtail millet make a better tasting and more filling meal.