Hydrangea robusta is native to China and the Himalayas. It grow in dense to sparse forests or thickets in valleys, along stream banks, or on mountain slopes or tops at elevations of 700-2800 meters above sea level.
Hydrangea robusta also called as Himalayan Tree Hydrangea, Hydrangea aspera subsp. robusta, is a species of the genus Hydrangea. This species was described by Joseph Dalton Hooker & Thomson in 1858.
IDENTIFY HYDRANGEA ROBUSTA PLANT
Hydrangea robusta is native to China and the Himalayas. It grow in dense to sparse forests or thickets in valleys, along stream banks, or on mountain slopes or tops at elevations of 700-2800 meters above sea level.
Himalayan Tree Hydrangea is a shrubs or small trees, which reaching 2-3 meters tall with branchlets, petioles, and inflorescences densely yellow-brown shortly hispid to spreading hirsute. The branchlets are brown, usually 4-angled, glabrescent. The petiole is thick, 3-15 cm; leaf blade elliptic, broadly so, or oblong-ovate to broadly ovate, 9-35 × 5-22 cm, papery, abaxially densely gray-white pubescent to sparsely brownish hispidulous, hairs sometimes longer and thicker along veins especially midvein, adaxially strigose, secondary veins 8-13 on both sides of midvein, base obtuse, truncate, rounded, or subcordate, margin irregularly doubly serrate, apex acute to acuminate.
Hydrangea aspera subsp. robusta blooms in July-August from the corymbose cymes inflorescences, lax, long, to 30 cm wide in fruit; peduncle thick, 4-angled. The sterile flowers with sepals 4(or 5), purplish to white, broadly ovate, orbicular, or broadly orbicular, 1.2-3.8 × 1.3-3.5 cm, margin entire, dentate, or serrate. The fertile flowers with calyx tube cupular, 1-1.5 mm; teeth ovate-triangular, 0.5-1 mm. The petals are purple, ovate-lanceolate, 2-3 mm.
The key to identify this species is: ovary completely inferior; capsule apex truncate; petals free; seeds winged at both ends, without transverse veins; leaf blade margin serrate; bracts not enveloping inflorescence in bud, lanceolate; shrubs or small trees; branchlets 4-angled, glabrous or with simple hairs; petiole long and thick.
HYDRANGEA ROBUSTA PLANT CARE AND CULTURE
Cultural information should only be used as a guide, and should be to be adapted to suit you. Your physical location; where you grow your plants, how much time you have to devote to their care, and many other factors, will need to be taken into account. Only then can you decide on the cultural methods that best suit you and your plants.
Light:
Hydrangea robusta love the warm morning sun, but they dislike the heat of the afternoon (can grow in full sun with adequate soil moisture). The best place to plant this species is in a sheltered location with sunny mornings and shady afternoons. Avoid planting directly underneath trees, which can lead to competition for water and nutrients. Although they can be successfully grown in full shade, they will not bloom well.
Temperature:
Keep the plants in a cool location, from 18° to 24°C. This plant grow well and are reliably winter hardy. Cold winters and late spring frosts can often kill flower buds, preventing plants from blooming in the spring.
Substrate, growing media:
Himalayan Tree Hydrangea are best planted in soil that has been amended with adequate amounts of organic matter, such as compost, leaf mold, or well-composted manure. While most hydrangeas grow better in soil that is lower in pH (acidic), they will tolerate higher pH soils (alkaline) quite well.
Watering and humidity:
Hydrangea aspera subsp. robusta prefer consistent moisture but dislike wet feet. Mulch to help conserve moisture and cool the root system. A two- to three-inch layer of mulch will help to conserve moisture.
Fertilizer:
Fertilizing is generally not recommended unless a nutrient deficiency is observed. This plants may need little fertilizer in rich soil with organic matter applied yearly. Avoid using too much nitrogen - this can encourage foliage growth at the expense of blooms.
Pruning:
Hydrangea robusta can be left unpruned and only blackened winter-injured tips removed in the spring. Dead or diseased branches can be pruned out at any time of the year.
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