The Blue Charm of Indigofera kirilowii: Ornamental, Edible, and Medicinal

Indigofera kirilowii, a member of the Fabaceae family, is a small shrubby plant.

It can grow to a height of 0.3-1 meter; its stem is cylindrical in shape, with young branches that are angular and, along with the leaf axis, both surfaces of the leaflets, and the inflorescence, sparsely covered with white T-shaped hairs.

The leaflets are opposite, broad ovate, ovate-diamond-shaped, or elliptical, blunt or acutely pointed at the tip, cuneate or broadly cuneate at the base, and powder-green underneath with conspicuous side veins and needle-shaped stipules.

The raceme is sparsely flowered, with a cup-shaped calyx, lanceolate-triangular sepals, and a pale red, occasionally white, corolla with elliptical standard petals.

The pod is cylindrical, and the seeds are reddish-brown and oblong. The blooming period is from May to July, with the fruiting period in August.

Indigofera kirilowii is distributed in countries like China, Korea, and Japan, often found on hillsides, in shrubby areas, sparse forests, or rock crevices.

It thrives in climates with abundant sunlight and is relatively tolerant of poor soil and drought. Common methods of propagation include seeding, cuttings, division, and layering.

Indigofera kirilowii has a bitter taste and a cooling nature, with the efficacy of reducing swelling, relieving pain, clearing heat, detoxifying, promoting bowel movements, and benefiting the throat.

It is used to treat symptoms like throat swelling and pain, lung-heat cough, constipation due to heat, hemorrhoids, and jaundice.

Its stem bark fiber is used for making rayon, fiberboard, and paper; its branches can be used for basket weaving; its seeds contain oil and starch; and its leaves are tannin-rich.

With its bright, pale red flowers that are fragrant and abundant, and its dense branches and leaves, it serves as an excellent source for honey and a plant for greening environments.

The flower buds can also be eaten, and its floriography represents charm, warmth, delicacy, youth, and vivacity.

I. Morphological Characteristics

In terms of morphology, this small shrub can reach a height of 0.3-1 meter; the stem is cylindrical and hairless, with young branches that are angular, covered with sparse white T-shaped hairs along with the leaf axis, both surfaces of the leaflets, and the inflorescence.

The pinnate compound leaves are 6-15 centimeters long; the petiole is (0.5-)1-2.5 centimeters long, the leaf axis is slightly flattened on top with a shallow groove, and is hairy or nearly hairless; stipules are lanceolate, 4-6 millimeters long, and deciduous early.

There are (2-)3-5 pairs of leaflets, opposite in arrangement, broad ovate, ovate-diamond-shaped or elliptical, 1.5-4 centimeters long, 1-2.3 centimeters wide, blunt or acutely pointed at the tip with an elongated tip, cuneate or broadly cuneate at the base, green on the upper surface, powder-green underneath, with sparse white T-shaped hairs on both sides, the midvein slightly raised above and more prominent below, and the side veins conspicuous on both sides.

The petiolules are 2.5 millimeters long and densely hairy; and the stipels are needle-shaped, 2-3 millimeters long, and persistent.

The raceme is 5-12(-20) centimeters long, with sparsely spaced flowers; the main flower stem is 1-2.5 centimeters long, the inflorescence axis is angular, covered with sparse white T-shaped hairs; bracts are linear-lanceolate, 2-5 millimeters long.

The flower stalk is 3-5 millimeters long and hairless; the calyx is cup-shaped, hairless outside, about 3.5 millimeters long, with the calyx tube about 1.5 millimeters long, the sepals lanceolate-triangular, fringed with hairs, the lowest sepal reaching 2 millimeters in length.

The corolla is pale red, occasionally white, with petals almost equal in length, the standard petal elliptical, 12-15(-17) millimeters long, about 7.5 millimeters wide, rounded at the tip, hairless outside, with short hairs on the edges, and the wing petals fringed with hairs; the anthers are broadly ovate with hair at both ends; the ovary is hairless.

The pod is brownish, cylindrical, 3.5-7 centimeters long, about 5 millimeters in diameter, hairless, with the inner fruit skin bearing purple spots and containing more than 10 seeds; the fruit stalk is spreading; the seeds are reddish-brown, oblong, about 5 millimeters long, and about 2.5 millimeters in diameter.

The flowering period is from May to July, with the fruiting period in August.

II. Growth Environment

The Plumbago auriculata thrives on hillsides, within sparse woods or shrubbery, or nestled in rock crevices.

III. Distribution

Plumbago auriculata is found in China, with its presence also recorded in countries like Korea and Japan.

IV. Growth Habits

Plumbago auriculata prefers sunny climates and can tolerate poor, drought-prone soils. It has a strong resistance to disease, can withstand wet conditions, and is not demanding in terms of soil quality.

V. Propagation Methods

Plumbago auriculata can be propagated through seeding, cuttings, division, and layering.

Seed Propagation

Fruit Collection and Seed Extraction

From September to October, fully matured pods are collected at any time, laid out to dry on a flat surface. Once the husks are dry, the seeds naturally disperse. Collect the seeds, remove impurities, and store them in a woven bag in a dry place.

Preparing the Seedbed

Choose a flat area with sandy loam to clay loam soil for a raised bed, facing either north-south or east-west. Gentle sunny slopes can also be used for horizontal beds.

The beds should be 1.2-1.0 meters wide, 0.15-0.2 meters high, and 20-50 meters long, depending on the terrain.

Spread poultry and livestock manure over the bed surface at a rate of 500 kg per 100 square meters. Turn the top 15-20 cm of soil to thoroughly mix it with the manure.

Seed Treatment

7-10 days before sowing, place the seeds at the bottom of a container. Gradually pour in water heated to 70°C, at ten times the volume of the seeds, and stir until it reaches room temperature.

The next day, drain the water and mix the seeds with three times their volume of sand in a woven bag, then store at 20-25°C to germinate.

Alternatively, 20 days before planting, soak the seeds in water at 25-30°C for 24 hours, mix with sand, and place in an environment of 5-10°C to germinate.

Another method is to soak the seeds in water at around 30°C for 24 hours, drain the next day, cover the seeds with a burlap sack or an old quilt, keeping the indoor temperature at 25-30°C.

Then, moisten the seeds with warm water every morning until germination occurs, and they are ready for sowing.

Sowing

From mid-April to early May, create 4 cm deep furrows along or across the bed with a hoe, spaced 25 cm apart. Scatter seeds into the furrows at a distance of 3-4 cm apart.

Cover with 2-3 cm of soil, pat down firmly, and aim for a sowing density of about 7 kg per acre. Seeds can also be broadcast by scattering evenly over the bed, then covering with 2 cm of soil.

Division Propagation

In early April, dig up perennial plants from the mountains or nursery, divide them into clumps of 3-5 individual seedlings, and plant tightly together in the nursery with 15×15 cm spacing between plants.

Firm the soil, water thoroughly, and maintain routine fertilization, weeding, and pest control measures.

VI. Cultivation Techniques

Sapling Transplantation

Site Selection and Bed Preparation

Choose flat or gently sloping ground with loamy soil. Apply about 4000 kg of farmyard manure per hectare, plow to a depth of 20 cm, and use a plow or tractor to create ridges 60 cm apart with a height of 15-25 cm.

Planting Saplings

In early April, dig up saplings sown in the previous year, trim any excessively long roots to a length of 10-15 cm, and prune the stems to a length of 15-20 cm.

Plant groups of 3-5 saplings in each hole. Space the holes 30-45 cm apart, with a depth of 10-15 cm, and firm the soil after planting.

Management and Maintenance

Post-Sowing Care

Cover the bed with a 1 cm thick layer of rice straw mats or wormwood. Spray water over the cover to moisten the top 6-8 cm of soil. After 3-5 days, when the surface dries out slightly, spray water a second time.

Once over 70% of the seedlings emerge, remove the cover. If May beetles are present, spread phoxim on the bed surface before the first watering after sowing, using 1 kg per 100 square meters to prevent them from disturbing the seeds, affecting germination and seedling numbers.

Thin out the seedlings if they are too crowded when they reach a height of 5 cm. In July and August, if aphids are a problem, apply insecticides like oxydemeton-methyl or imidacloprid. From seedling emergence until the end of August, weed by hand or hoe as needed.

In early July, evenly spread urea over the bed at a rate of 15-20 kg per acre and water to prevent burning the seedlings if there’s no rain after application.

At the end of October or the beginning of November, water the bed thoroughly to prevent winter drought and desiccation of the young plants.

Post-Planting Care

For flat ground, irrigate slowly and thoroughly immediately after planting, followed by a second watering a few days later.

For sloped areas, create a basin on the ridge when planting and fill it with water, then water again on the third day and seal the soil once the water has infiltrated.

During the growing season, weed and loosen the soil 3-4 times to ensure that there are no pests and the soil remains loose. From June to August, if aphids or other leaf-eating insects are detected, apply insecticides like esfenvalerate or imidacloprid.

In the third year after planting, if the leaves turn yellow, dig 15 cm deep pits 15 cm away from the plant along the ridge, and apply urea or diammonium phosphate, using 300-450 kg per hectare.

In April after winter, the tips of the shoots often dry out, so prune the main shoots of the seedlings before they start to sprout.

VII. Main Value

Medicinal Value

Bluebell roots taste bitter and cool in nature, offering anti-inflammatory and analgesic effects, as well as heat-clearing and detoxifying properties.

They facilitate bowel movements and soothe sore throats. The herb is used to treat symptoms like throat inflammation, cough due to lung heat, constipation, hemorrhoids, and jaundice.

Properties and Meridians

Bitter, cold.

Functions and Indications

Clears heat, detoxifies, reduces swelling, relieves pain, and promotes bowel movements. It’s indicated for throat soreness, cough with lung heat, jaundice, constipation due to heat accumulation; externally for painful swollen hemorrhoids and bites or stings.

Dosage and Administration

5-15 grams; for external use, apply an appropriate amount of root powder or fresh root juice to the affected area.

Chemical Components

Seven compounds have been isolated from the stem: 2,3,4,6-tetra-O-(3-nitropropanoyl)-α-D-pyranoglucose, luteolin-7-O-glucoside, 2,3,6-tri-O-(3-nitropropanoyl)-α-D-pyranoglucose, 2,6-di-O-(3-nitropropanoyl)-α-D-pyranoglucose, daucosterol, lupeol, and β-sitosterol.

Five compounds from the leaves: kaempferol-3-O-rutinoside, quercetin-3-O-glucoside, rutin, 2,3,6-tri-O-(3-nitropropanoyl)-α-D-pyranoglucose, and daucosterol.

Thirteen compounds from the roots: cibarian, hetranthin A, ethyl 3-nitropropionate, 6-acetyl-2,3-di-O-(3-nitropropanoyl)-α-D-glucopyranose, 2,3,4,6-tetra-O-(3-nitropropanoyl)-α-D-glucopyranose, coronarian, corollin, 3-nitropropionic acid (VIII), stigmasterol-3-O-glucoside, daucosterol, β-sitosterol, lupeol, and betulinic acid.

Edible Value

The buds of the bluebell plant are also edible.

Economic Value

Bluebell plant’s stem bark provides fibers for the production of rayon, fiberboard, and paper; its branches can be used for basketry; seeds contain oil and starch; leaves are rich in tannins. The bluebell plant is an excellent source of nectar for bees.

Ornamental Value

The bluebell plant is a rare summer-blooming flower in the north, with vibrant colors, large blossoms, fragrance, and lush foliage. Its blooming period lasts 50-60 days.

Ideal for hedges, it’s also suitable for greening along highways, railways, slopes, and roadsides, as well as being material for flower beds and borders. Its floral language conveys charm, warmth, delicacy, youth, and vivacity.