Premna microphylla aka Turtledove Tree

Premna microphylla grows as a small tree or shrub typically reaching 2–6 m tall and around 3 m wide, with an active growing season from March to November. Bonsai growers describe it as a vigorous, root-aggressive species with fine ramification, light beige bark, and small opposite leaves that suit shohin-sized trees. Branchlets are pubescent when young but become smooth with age.

The species is native to southern and central China — including Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangxi, Sichuan, Taiwan, Yunnan, and Zhejiang — as well as Japan, where it ranges from western Honshu south through Shikoku, Kyushu, and parts of the Ryukyu Islands. Typical habitat is mixed forests on mountain slopes at 200–1,000 m elevation, with coastal populations near the sea in Japan.

Keep the soil consistently moist year-round and never let it dry out completely, since P. microphylla is a vigorous grower with an extensive root system. Reduce watering slightly during winter dormancy, and avoid hard, mineral-rich water that can build up salts in the substrate.

Plant in a well-draining substrate such as a standard bonsai soil mix; the species prefers slightly acidic to acidic conditions in the wild. Repot every two or three years in spring as the buds swell, trimming back about one-third of the roots.

Premna microphylla is a subtropical to tropical species and requires temperatures consistently above 50°F (10°C). It is not reliably winter-hardy outdoors in cold-temperate climates and should be moved indoors or into a heated greenhouse before frost.

Indoor specimens benefit from relatively high ambient humidity along with warmth and bright light. Outdoors in its native East Asian range it grows in humid forest understory and coastal habitats.

Feed during the active growing season with solid organic fertilizer applied roughly once a month, or with liquid fertilizer applied weekly. Reduce or stop fertilizing in winter when growth slows.

The plant grows actively from March through November and slows down in winter. During warm months, give it full sun, regular watering, and steady feeding; in winter, water more sparingly, reduce fertilizer, and protect from temperatures below about 10°C.

Crushed or rubbed leaves emit a strong, unpleasant odor — the source of the Japanese name ハマクサギ ("beach stinking tree") and Chinese vernaculars such as 臭黄荆 ("stinky yellow thorn"). The aroma is characteristic of the mint family and reflects an essential oil rich in compounds like β-cedrene, limonene, α-guaiene, and α-cyperone.

The plant produces small, hermaphroditic, pale yellow flowers in conical terminal panicles. Each flower has a short, cup-shaped, purplish-green 5-dentate calyx and a funnel-shaped, zygomorphic corolla about 7 mm (6.5–9 mm) long. Flowering occurs from May to October in China and around May–June in Japan.

The species is noted for being "extremely variable in leaf characters," and several names once treated as distinct — including Premna formosana, P. japonica, P. luxurians, and P. microphylla var. glabra — are now placed in synonymy under P. microphylla.

Outdoors, place in full sun in an airy spot, sheltering smaller specimens from intense midday heat. The species is suitable for outdoor culture only in frost-free areas; in cooler climates it must be brought inside before temperatures drop below about 10°C. Native habitat is mixed mountain forest at 200–1,000 m elevation, with coastal populations in Japan.

Repot every two or three years in spring just as the buds begin to swell. Use a standard bonsai soil mix and prune back roughly one-third of the root mass to keep the plant vigorous in a container.

Propagate from seeds or from softwood/semi-hardwood cuttings. Air-layering is also a workable method for producing larger specimens with established trunks.

Premna microphylla is generally pest-resistant and has no major documented diseases or insect pests. Occasional issues seen in cultivation include aphids, scale insects, red spider mites, and powdery mildew; in the wild, sika deer sometimes browse the foliage.

Flowers are insect-pollinated, with documented visitors including the carpenter bee Xylocopa amamensis, the wasp Cerceris yuwanensis, and the bee Hylaeus insularum. Pollination occurs primarily during the May–August flowering window.

The leaves are the edible part and are unusual in their very high pectin content (30–40%) and protein content (~13.48%). Crushed leaves are mixed with water, strained, and set with culinary ash to make a green tofu-like gel called 神仙豆腐 (immortal tofu) or 观音豆腐 (Guanyin tofu), regarded as a refreshing summer food in southern China. Pectin extracts are also studied for use in edible films and dietary applications.

In traditional Chinese medicine, the roots, stems, and leaves of P. microphylla are used for detoxification, reducing swelling, controlling bleeding, and treating dysentery, appendicitis, and various infections. Modern peer-reviewed studies report antioxidant, anti-inflammatory, antimicrobial, and gut-microbiota-modulating activity from leaf pectin and essential oils, with experimental work also showing photoprotective effects against UVB-induced skin aging in mice.

Beyond food and medicine, P. microphylla is one of the most popular species for shohin-sized bonsai, prized for its small leaves, fine ramification, and beautifully textured light beige bark. The leaves' unusually high pectin content (30–40%, compared with 10–15% for apple pomace and 20–30% for citrus peel) makes them a candidate industrial pectin source. In Kagoshima Prefecture, Japan, branches are traditionally hung in livestock buildings to repel flies, taking advantage of the foliage's strong odor.

With a bit of knowledge and dedication, you can successfully care for Turtledove Tree, making it a rewarding choice for those seeking a moderate challenge.

Turtledove Tree thrives in bright and direct sunlight. To ensure your plant receives enough light to survive, place it less than one foot from a window. The current weather in your area may affect the placement in your home. For example, if you live in a region that has longer and more intense periods of sunlight, then you may want to place the plant farther away from the window to avoid direct sunlight and reduce the risk of sunburn. Alternatively, if you live in a region with relatively milder temperatures and less intense sunlight, then you may be able to place the plant closer to the window for increased exposure. Ultimately, the current weather in your area should be taken into consideration when determining the best placement for your Japanese Premna.

Turtledove Tree is not known to cause harm to humans or pets.