Japanese ivy, also known as Hedera rhombea or songak, is an evergreen plant that climbs like a vine and belongs to the Araliaceae family. It’s different from other ivy plants because it keeps its leaves even in the winter, which is why it’s called “winter ivy.” People often use Japanese ivy to decorate their gardens. They grow up to 33 feet in height. It was first described by Friedrich Anton Wilhelm Miquel (1811–1871).
A Distinct Plant
In the scientific name Hedera rhombea, the species name rhombea comes from the Greek quadrilateral called “rhombus”. On the other hand, the genus name hedera literally means “ivy” in Latin.
As for its Japanese names, “kizuta” comes from the fact that it’s a sturdy, woody plant, setting it apart from other ivy plants that lose their leaves in the grape family. It’s also sometimes called “fuyuzuta” because it stays green during the winter.
What It Looks Like and Where It Grows
Woody vine that survives winters; its stem sprouts a plethora of adventitious roots that it uses to scale vertical surfaces like other trees, rocks, and buildings.
Now, let’s talk about what Japanese ivy or Hedera rhombea looks like and where it grows. Japanese ivy is a vine with thick, tough leaves that are held by 0.60 to 2 inches long (1.5–5 cm) petioles. These leathery leaves grow along the stem. Depending on how old the branches are, the leaves can be different shapes.
On young branches, they’re oval or rhombic-ovoid with 3–5 sections on the leaf tips. But on older branches, they’re more like ovate-lanceolate with pointed tips and no sections. The blades of the leaves are usually 1 to 3 inches long (3–7 cm) and 0.8 to 2 inches wide (2–5 cm).
In the fall, around October to November, Japanese ivy produces small yellowish-green flowers in clusters at the ends of its stems. Many florets are found on the one to several cymes put out at the tip of the stem. These flowers have five petals and are about 0.12 inches (3 mm). There are five stamens.
The flowering season is autumn (around October–November). One to several cymes are put out at the tip of the stem, and many florets are attached. The flowers have 5 petals, are yellowish green, and the length of the petals is 3 mm. There are five stamens.
The fruiting period is in the spring of the following year (around April), when it produces dark, ripe, spherical fruits with a diameter of 0.25 to 0.28 inches (6 to 7 mm).
Where Japanese Ivy is Found
Japanese ivy grows in East Asia, specifically in countries like North Korea, South Korea, Japan, southern China, and Taiwan (“Taiwan ivy”). In Japan, you can find it in the southern parts of Hokkaido, Honshu, Shikoku, Kyushu, and the Ryukyu Islands.
This plant also grows on the natural wonder of South Korea called Seongsan Ilchulbong, which is included in the World Heritage List.
The Japanese ivy plant can be found in low-lying areas and in the mountains. It prefers the shady slopes of cloud forests, particularly those with laurel trees. This plant is tough, it can handle the cold, and it even does well in places with a lot of shady areas.
Other Similar Plants
There are many other plants like Japanese ivy. One of these similar plants is called Hedera canariensis, and in Japan, it’s known as “Okamezuta.”
People like to plant it in gardens and pots for decoration, and it goes by different names like Canary Island ivy, madeira ivy, and Canary ivy. It’s known for being able to grow well even when it’s dry, and some varieties with different-colored leaves are especially popular.
Uses
Japanese ivy is grown as a garden ornament and incorporated into floral arrangements. Also, it has a therapeutic application.
In Japan, people use this plant to treat nosebleeds. What’s interesting for medicine is that this plant contains certain compounds that are common in the Hedera genus. One of them is a compound called alpha-hederin, which is a type of triterpenoid saponin.
This alpha-hederin helps protect cells called lymphocytes from mutations when they’re grown in a lab. It also slows down the growth of certain mouse melanoma cells and non-cancerous mouse fibroblasts. Additionally, after being exposed to this compound for 24 hours, it changes the cellular features of a fungus called Candida albicans.
Taxonomy
In 1843, Siebold & Zucc. published the first description of Hedera rhombea.
Etymology
- Hedera: generic name given to ivy.
- rhombea: Greek epithet; ῥόμβος (rhombos): rhombus.
Cytogenetics
The number of chromosomes in Hedera rhombea is 2n=48.
Synonymy
Rhombea has a variant called Hedera Helix. The old name for this plant was Hedera pedunculata. Some of its subspecies may one day be recognized as separate species.
Varieties
Hedera rhombea is a species of Magnoliopsida described by Friedrich Anton Wilhelm Miquel and given its original name by Philipp Franz von Siebold and William Jackson Bean.
- Hedera rhombea var. formosana (Nakai) Li: It is distributed mainly in Taiwan.
- Hedera rhombea var. rhombea (Miq.) Bean: It is distributed mainly in Japan and Korea.
