Sullu spurge, or Euphorbia royleana, is a deciduous, cactus-shaped succulent. Leafy stems grow from the top of the plant, which loses its leaves in hot or cold periods. This plant produces small, greenish-yellow flowers. It has spines on its stems and is considered mildly toxic.
I. Appearance and Characteristics
Euphorbia royleana is a species of flowering plant in the family Euphorbiaceae. It is also known as Sullu spurge, and Royle’s spurge. It is a succulent and almost cactus like in appearance although unrelated. It grows right across the Himalaya mountains from Pakistan, India, Bhutan, Myanmar, Nepal to western China. It prefers dry and rocky slopes between 1000 and 1500 meters, but has been found up to 2000 meters.
Euphorbia royleana is a deciduous, cactus-like, shrub or small upright trees up to 2-5(-7) m high, which is armed with short prickles along its stems. It has a stout trunk and is glabrous except for the flowers (cyathia). The cyathia are small greenish-yellow, 3-4 appear in almost stalkless clusters in leaf axils.
It has succulent segmented branches in whorls, which are green, 4-7(-8) cm thick, with branching from the upper parts. The stems have ribs 5(-7), angles more or less undulately winged with rounded teeth/tubercles. It has stout tap roots.
The stems become leafless during hot and cold seasons and the leaves are alternate, apically clustered. They are produced in the moist season and soon fall. They are usually not seen when in flower. The leaf blade is fleshy oblanceolate, spathulate, or spoon-shaped 5-15 long, 1–4 cm wide and slightly succulent. The base is attenuate, the margin entire, and the apex obtuse or subtruncate. Veins are inconspicuous. The petiole is absent.
Stipular spines are present in small pairs on the edges on distinct shield, with broad flat faces between, 3–5 mm long.
The cyathia, or false flowers, are greenish-yellow, almost stalkless, 3-4 in subterminal cymes in leaf axils. They are peduncles about 5 mm long. Cyathophylls as long as involucre, membranous. Involucre ca. 2.5 × 2.5 mm. Nectar-glands 5, transversely elliptic, dark yellow. Seed capsules are trigonous, 1-1.2 × 1-1.5 cm, light reddish brown, smooth and glabrous. The seeds themselves are 3-3.5 × 2.5–3 mm, brown, adaxially striate; caruncle absent.
II. How to Grow and Care
Sunlight
Sullu spurge thrives best in conditions of full sun, where it can bask in the sun’s rays throughout the day. This species is well-adapted to bright light, which promotes healthy growth and optimizes photosynthesis. While sullu spurge is robust and can manage in less than ideal light, extended exposure to dim conditions could compromise its vigor, potentially leading to weaker stems and sparse foliage. Outdoors, sullu spurge favors sunny spots that mirror its natural habitat, enabling it to grow to its full potential. Its leaves may exhibit adaptive behaviors to manage intense light, such as orientation changes or developing a protective waxy coating to prevent water loss.
Temperature
Genus Euphorbia is very large and diverse, so its different species can be found in various habitats, but the majority are well-adapted to a temperature range of -29 to 4 ℃. Many spurges, in spite of having succulent leaves, cannot handle long periods without moisture and need to be watered weekly during hot summer days. Some cactus-like species are well adapted to high temperatures and prolonged dry periods, but most species used for landscaping and decorative gardening require more moisture for proper development.
Watering
Originating from arid regions, sullu spurge has adapted to thrive with minimal moisture, exhibiting a high drought tolerance. Its water storage capabilities allow it to be watered sparingly, specifically once every three weeks. This infrequent watering schedule reflects its natural habitat’s scarce rainfall patterns. As an outdoor plant often found in xeric landscapes, sullu spurge benefits from a well-draining soil composition that mimics its native dry conditions, ensuring excess water does not accumulate around its roots.
Soil
Sullu spurge thrives in well-drained soil. A suitable mix can include equal parts of succulent & cactus soil, coarse sand, and perlite to enhance aeration and drainage. If perlite is unavailable, pumice or even fine gravel can be substituted. A layer of gravel at the bottom of the container will also improve drainage. Occasional addition of a balanced, slow-release fertilizer will aid in growth without the need for frequent application. Regular monitoring to prevent water-logging is crucial for sullu spurge’s health.
Fertilizing
For sullu spurge, utilize balanced succulents and cacti food to foster robust growth. Bi-annual fertilization, in spring and summer, caters to sullu spurge’s active growth phase. A diluted half-strength solution prevents over-fertilization. With seasonal shifts, taper off in autumn, suspending in winter as sullu spurge’s growth pauses. Always irrigate before fertilizing to protect sullu spurge’s roots. Adhering precisely to instructions avoids nutrient burn, ensuring sullu spurge’s vigor and longevity.
Planting Instructions
Dig a hole twice as wide as the plant’s root ball before planting. Then, turn the container with sullu spurge upside down and let the plant slowly fall into your hands. Place the plant upright in the hole and slowly fill in around the roots with loose and fertile potting mixture, adjusting the planting depth until it is just right. Water it once. Do not overwater, as standing water is not good for the plant.
Propagation
Sullu spurge is a resilient and versatile specimen from a genus known for its sap-containing characteristics, which can be effectively propagated through cuttings. Ensure to handle it with care to avoid irritating sap exposure. For successful propagation, use healthy and mature stem segments, allow the cut surface to callus before planting into a suitable potting mix that provides good drainage. Regular attention to moisture levels without overwatering will encourage root development, resulting in robust growth for this species.
Transplanting
For sullu spurge, late spring to early summer (known as ‘S2-S3’) is the ideal transplanting season, as warmth and increasing daylight optimize growth. Choosing a sunny, well-drained location is critical. If you’re transplanting, do so cautiously due to its sensitive root system. Remember, the sullu spurge flourishes with care!
Repotting
Repot sullu spurge when it outgrows its container, typically every 2-3 years. As a sturdy, slow-growing succulent, it prefers larger pots which provide ample space for its taproot system. The best time to repot is during the warm growth season. Post-repotting, sullu spurge requires minimal water until new growth is seen, ensuring successful adaptation with less stress.
III. Uses and Benefits
It is a medicinal shrub used in Nepal locally known as siyuri or siudi. Its latex has purported molluscicidal properties.
Several researchers have noted that Euphorbia royleana has been observed growing near rock face collection sites of the Ayurvedic resin shilajit in the Himalayas. The plant is the likely origin of shilajit as its gum has a similar composition to the resin.
IV. Harvesting and Storage
Some species of Euphorbia can be cut for fresh flowers or foliage, such as snow-on-the-mountain (Euphorbia marginata), Euphorbia fulgens and Euphorbiaformosana. When harvesting cuttings, remember to wear gloves, as the sap can be irritating to the skin. It can be cut from the base of the stem. Soak the end of the cutting in hot water for 10 seconds to stop the milky sap from oozing. The vase life for the cutting will be about 5-7 days, and some flower food can extend its life.
When the fruits of Euphorbia plants are ripe, they burst and scatter the seeds over a large surface area. In order to harvest all the seeds, the individual fruits or the entire plant must be wrapped in in nylon, gauze, or similar material before the ripe fruit bursts and releases the seeds.