The Japanese Sago Palm (Cycas revoluta), also known as King Sago, is a dioecious plant of prehistoric origin, with very slow growth, which makes it highly valued in the market. The older the specimen, the higher its value. Native to southern Japan, including Kyusha and the Ryukyu Islands, this species is a true living fossil, dating back approximately 200 million years. During the Age of Dinosaurs, these plants were already present, making them one of the oldest lineages of seed plants still in existence. Cycas revoluta mainly inhabit hill slopes, growing in clumps at altitudes between 328 and 1640 feet (100 and 500 meters). Although it resembles a palm due to its appearance, with a cylindrical trunk crowned with large pinnate leaves, it is not a true palm but a member of the ancient family Cycadaceae.
The genus name, Cycas, derives from the Greek word “kykas,” which is possibly a transcription error of “koikas,” meaning “palm.” This name reflects the palm-like appearance of the plant, despite its taxonomic relationship being closer to conifers (pines and cypresses) than to true palms. The specific epithet revoluta comes from Latin and means “curved backward,” referring to the distinctive characteristic of the leaves, which curl downwards.
The trunk of C. revoluta is usually small or subterranean, but as the plant ages, the trunk elongates above the ground, reaching up to 20-23 feet (6-7 meters) in very old specimens. This growth is extremely slow, taking between 50 to 100 years to reach such dimensions. The trunk is covered by a dense and furry layer, which is actually the accumulation of old leaf bases. This feature contributes to the plant’s resilience, protecting it against water loss and extreme temperatures.
In adult plants, the leaves can measure between 20-60 inches (50 and 150 cm) in length and form a rosette at the top of the stem. The leaves are pinnate, composed of narrow, intensely green, shiny, and rigid leaflets, which measure between 3-7 inches (8 and 18 cm) in length, with strongly recurved margins. The basal leaflets transform into spines, providing a natural defense against herbivores. The petioles that support the leaves are between 2-4 inches (6 and 10 cm) long and have small protective spines. Young plants produce leaves intermittently in growth spurts throughout the year, while mature plants produce new leaves only once a year.
The root of C. revoluta is coralloid due to its branched, coral-like appearance. These roots establish a symbiosis with the cyanobacterium Anabaena, which allows for efficient nitrogen fixation, an essential nutrient for the plant, even in poor soils. The tannin-rich cells around the layer of cyanobacteria help resist infection by these microorganisms, maintaining the balance of this symbiotic relationship.
Japanese Sago Palms are dioecious, meaning there are separate male and female plants. Male plants produce pollen cones (strobili), while female plants develop groups of megasporophylls. Pollination can occur naturally through insects, although it is rare, or artificially. The male plant is known for its erect, elliptical-shaped, yellow cone, which can reach up to 18 inches (45 cm) in height, while the female plant produces a rosette-shaped inflorescence.
The ovaries, which are protected at the top of the female plant during flowering, are very difficult to pollinate naturally, so almost 100% of the fruits obtained in residential gardens are sterile. Additionally, female plants are generally found in cultivation, with male plants being rarer. Seed production is a long process; it is usually done in specialized nurseries. The seeds, which are the size of golf balls and bright orange, take about a year to mature after pollination.
In landscaping, it works well as an isolated plant and in garden groups or pots. It is valued for its hardiness, symmetrical appearance, resembling a small palm, and slow growth, making it suitable as a focal point in gardens, whether planted individually or in groups for a dramatic effect. Its ability to thrive in sandy, well-drained soils, under full sun or partial shade, makes it adaptable to tropical to temperate climates. A downside is that in some places it has become overused in gardens, reducing diversity and the choice of native plants.
The Cycas revoluta is often used in rock gardens, where its architectural form adds structure and interest. Due to its slow growth and low maintenance needs, it is preferred for patios, balconies, and terraces, planted in pots, bringing a touch of green to both indoor and outdoor spaces. The drought tolerance of the Japanese Sago Palm, once established, further increases its appeal in landscapes designed for water conservation. Its slow growth makes it a very interesting species for the art of bonsai.
The common name sago is due to the fact that the pith of the trunk of this plant has been used to produce sago (or tapioca), a starch-rich food, in the form of small round pearls, used in sweets, teas, juices, breads or even to thicken broths. The trunk pulp contains edible starch, used in the production of sago after a careful washing process to remove toxins. However, it is important to note that all parts of the plant are highly toxic if ingested, especially the seeds, due to the presence of toxins such as cycasin. Due to this complicated washing process and the risks involved, sago from Cycas is less common than sago from cassava (Manihot esculenta) or True Sago Palm (Metroxylon sagu).
Regarding cultivation requirements, Cycas revoluta prefers sandy, well-drained soils with some organic matter to improve fertility. Good drainage is essential to prevent root rot. Periodic irrigation is recommended for plants grown in pots, indoors, or young and newly transplanted plants. Once well established, it becomes drought-tolerant and can be grown in both full sun and partial shade, although it needs bright light when grown indoors.
Its tolerance to soil salinity and sea spray makes it an ideal plant for coastal landscaping. Pruning is minimal and consists of removing older and yellowed leaves. The leaves can discolor from sunburn if the plant is abruptly moved from indoor environments to direct sunlight. To move a plant’s position, it is best to do so gradually over several weeks and preferably in winter.
The Japanese Sago Palm is a slow-growing plant, forming a robust trunk over decades. It is also very long-lived, capable of living over 100 years. This species is widely cultivated in temperate and subtropical regions, both outdoors and in greenhouses. It is resistant to moderately cold temperatures, but frost damage can occur if temperatures drop below 14 °F (-10 °C). Additionally, hailstorms often completely destroy its rigid leaves. In temperate climates, it is common for the plant to lose its leaves during winter and regrow in spring.
Japanese Sago Palms are deer-resistant due to their rigid foliage and spines at the base of the leaves. However, they are often victims of scale infestations that can decimate the plant over time. The use of insecticides and mineral oil sprays combats these pests.
Regarding propagation, Cycas revoluta can be multiplied by seeds or by removing basal shoots. Propagation by seeds is a slow process, characteristic of Cycas, but it is common in commercial cultivation. Basal shoots, or pups, emerge at the base of the mother plant and can be separated and replanted to start new plants, which is the method most commonly used by amateur gardeners.
