Tabernaemontana divaricata: From Botanical History to Care Techniques

Tabernaemontana divaricatais a shrub from the Apocynaceae family, featuring grayish-green branches. The leaves are elliptical or oblong-elliptical, dark green on the surface and light green on the underside, with a flat appearance.

The flowers, which are usually paired, bloom in cymes from the leaf axils with long, oval sepals fringed with ciliate margins, and boast white corollas.

The fruit is elongated, with the flowering season spanning from June to November and fruiting occurring in the fall. The plant gets its name from the creased edges of its corolla lobes, which are reminiscent of dog’s teeth.

Tabernaemontana divaricata

This plant thrives in warm and humid conditions, is intolerant to cold, prefers semi-shade, and is not particular about soil type, though it favors fertile, well-drained acidic soils, typically found in mountainous shrublands. Propagation is mainly done through cuttings.

Crepe Jasmine is known for its sour taste and cooling properties, and is used medicinally to reduce fever and blood pressure, detoxify, and reduce swelling. It can be used to treat sore throats and bruises.

With its dense foliage, compact growth, and pure, elegant white flowers, Crepe Jasmine is highly ornamental, especially when in full bloom, offering a long flowering season and aesthetic value.

Tabernaemontana divaricata

It also holds significant economic value and is widely used in landscaping, suitable for planting along forest edges, roadsides, courtyards, or as hedges and foundational planting material. It is also an excellent choice for potted plants.

Crepe Jasmine is classified as an Endangered (EN) species and is under protection.

I. Botanical History

The Crape Jasmine is named for its fringed corolla lobes, which resemble dog teeth.

II. Morphological Characteristics

This shrub grows to heights of 1-3 meters and contains a milky sap; its entirety is hairless. Branches and twigs are pale grey with lenticels and, upon drying, exhibit longitudinal striations.

Inter-nodal lengths range from 1-10 centimeters. Early-deciduous stipules are ovate, with a broadened base that is fused, measuring about 1 millimeter.

Leaves are also early-deciduous, often clustered at the tips of the upper twigs, elliptical to oblong, tapering to a short point, with a wedge-shaped base, measuring 3.5-4.5 centimeters in length and 1-1.7 centimeters in width (up to 6 centimeters by 2 centimeters at their largest), flat except for the central vein; with 8-10 pairs of lateral veins; petioles are 5-10 millimeters long.

The cymose inflorescences are axillary or pseudoterminal, with solitary or paired flowers, without a common peduncle or one less than 5 millimeters in length; bracteoles are ovate, 1 millimeter long; flower buds are cylindrically acute; the inner surface of the calyx at the base has many glands, sepals measure 4 millimeters; the corolla is white, the corolla tube is 20 millimeters long, the lobes are nearly quadrangular-triangular, nearly spoon-shaped at the base, with imbricated arrangement at the top, each lobe measuring 13 millimeters in both length and width; stamens are attached near the base of the corolla tube, three times shorter than the tube, the anthers are linear-lanceolate, slightly divergent at the base; the ovary is 2.5 millimeters long, with the carpels fused at the lower part and separate at the upper, tapering and then merging into a short style, which is short and cylindrically shaped, measuring 0.8 millimeters in length, with a bifurcated stigma that is 1 millimeter long.

The fruit is paired follicles, linear-lanceolate, 2 centimeters long and 6 millimeters in diameter. The flowering period is from April to September, with the fruiting period from July to November.

III. Growing Environment

The Crepe Jasmine thrives in humid, warm conditions with ample sunlight, tolerating partial shade but not cold. It grows best in fertile, well-drained acidic soil, particularly in mountainous shrubbery at elevations ranging from 1,000 to 1,600 meters.

IV. Distribution Range

Native to China, Myanmar, Thailand, Nepal, Bangladesh, Bhutan, and India, the Crepe Jasmine is now widely cultivated in the tropical and subtropical regions of Asia.

V. Propagation Methods

The Crepe Jasmine can be propagated via cuttings or air layering, with cuttings being the primary method. In South China, propagation is viable from spring to autumn, with spring being the optimal time.

Choose robust branches that are 1-2 years old and cut them into 15-centimeter segments, leaving 1-2 leaves at the top.

Trim two-thirds off each leaf and cut the upper end flat, approximately 0.8 centimeters above a bud, and shape the lower end like a horse’s ear, ensuring a smooth cut to facilitate healing.

Since the cuttings exude a milky sap, immerse the cut end in water for 2 hours to wash it off, then plant densely in a moist sand bed, directly into a nursery bed, or containers. After planting, provide shade and mist spray.

No need for hormonal treatments; roots should emerge and sprouts appear within about 25 days, with a survival rate exceeding 85%.

Once rooted in a sand bed, the cuttings can be moved to a nursery bed or containers. When seedlings reach 20 centimeters, pinch the top bud to encourage lateral branch growth.

VI. Cultivation Techniques

Transplanting: In April, move the Crepe Jasmine outdoors. Repot every 1-2 years, adding compound fertilizer or bean cake as a base and prune dead or weak branches, then keep in a semi-shaded area.

Soil: While Crepe Jasmine isn’t particular about soil, it flourishes best in fertile, loose, well-drained acidic soil.

Watering: Maintain soil moisture, avoiding complete dryness before watering. During summer, mist the surroundings frequently to increase humidity.

Temperature: The optimal growth temperature for Crepe Jasmine is above 10°C. Below this, leaves may yellow, and branches can suffer frost damage under 0°C.

Light: Crepe Jasmine enjoys a warm, moist climate and plenty of sunlight. Place it where it can absorb indirect sunlight.

During intense summer heat, keep it in partial shade to prevent leaf scorch. Adequate lighting is crucial for maintaining vibrant leaf color; otherwise, leaves may turn dull and drop off.

Fertilizing: Favoring fertile soil and featuring a long blooming period, the Crepe Jasmine requires timely fertilization. From May to September, alternate between compound fertilizer and manure water every 7-10 days.

After moving indoors at the end of October, water every 5-7 days to keep the soil slightly moist and ensure good lighting.

VII. Pest and Disease Control

Dogbane is commonly afflicted by pests such as thrips and aphids.

To combat aphid infestations, a variety of measures should be taken to halt their damaging activities, including the following points:

Eradicating aphids should begin during the overwintering period of the flowers for increased effectiveness. Relying solely on control measures during the peak infestation seasons of spring and fall is less impactful.

Newly introduced flower species and seedlings should be rigorously inspected to prevent the intrusion of foreign pests. Soil and old flower pots must be disinfected to eliminate any residual insect eggs.

Pruning should be combined with the thorough removal and incineration of withered flowers, diseased branches, and leaves where aphids or their eggs may reside or lurk.

As resistance to pests varies among different flower species, it is advisable to choose varieties that are resistant to diseases and pests, thereby reducing the harm caused by aphids and saving on pesticide costs.

At the first sign of a minor aphid presence, they can be removed with a brush dipped in water or by tilting potted plants under running tap water for a rotational rinse.

This not only eliminates aphids but also cleans the leaves, enhancing their aesthetic value and promoting foliar respiration. If possible, natural enemies such as ladybugs and lacewings can be used for control.

In the event of a large aphid infestation, immediate isolation and treatment with remedies or traditional methods should be enacted.

Specific measures include preparing a tobacco leaf solution at a ratio of 1:15, steeped for 4 hours before spraying; a solution of laundry detergent, urea, and water at a ratio of 1:4:400 for spraying; or using a 10% Dimethoate EC diluted to 1000 times, Malathion EC at 1000 to 1500 times dilution, or Diazinon oil emulsion at 1000 times dilution for spraying.

For aphids like the peach-potato aphid that are coated with a waxy substance, any applied pesticide should be mixed with a 0.1% neutral soap solution or laundry detergent.

VIII. Main Varieties

The varieties include both single and double-flowered ‘Fore-pleno’ types, as well as the variegated dogbane (Tabernaemontana divaricata ‘Variegata’), which features leaves with yellow streaks, offering both floral and foliage beauty.

The South Sea dogbane (Tabernaemontana pandacaqui poir) is an evergreen shrub with lanceolate leaves, and its corolla has 5-6 lobes, resembling a single-petaled pinwheel.

IX. Primary Value

Medicinal

The entire dogtooth violet plant contains indole alkaloids, while its seeds are rich in evatromonoside, which are known for their diuretic, swelling-reducing, cooling, and heat-dispelling effects.

They are used to treat sore throats, high blood pressure, bruises, and sores, among other ailments.

Ornamental

With its lush foliage and compact growth, the dogtooth violet blooms in pristine and elegant white flowers. It is particularly striking when in full bloom and has a long flowering period, offering significant ornamental value.

The plant also holds high economic worth and is widely used in gardens. It can be grouped at the edge of forests, along roadsides, in courtyards, or planted as hedges or foundational landscaping materials, and it makes an excellent potted plant.

X. Conservation Status

The dogtooth violet is listed in the International Union for Conservation of Nature’s Red List (IUCN) as Endangered (EN).

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