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The Plant that Hooks - Rose Mallow

Green Country Vol. 130 (Feb 2018)

Many of us may have encountered the nuisance of being hooked onto by countless granular items on our clothes while visiting the countryside. In the past, kids were fond of collecting these little meteor-hammer-like fruits as "weapons"—particularly against people with long hair who would then have to spend a great deal of time to take the burrs off their hair. The "sticky" plant, quite unlike its unwelcoming nature, has an elegant name – Rose Mallow.

Rose Mallow (Urena lobata), of the Malvaceae family, is a common shrub native to Hong Kong. The one-metre high plant can be easily found by the roadside or in abandoned fields. The species bears flowers and fruits from July to February of the following year. The stamen and pistil fuse into a long stalk, while the stigma is divided into five at the tip, with anthers clustered below. This is a characteristic of the Malvaceae family. The leaves are of varied shapes; those growing near the lower part of the stem are more rounded, shallowly 3-lobed at the apex; those growing in the middle part along the stem are broadly ovate; and those at the top are lanceolate with serrated margins.

The fruits are depressed globose in shape, turn brown and divide into five pieces upon ripening. There are minute hooks on the surface, resembling meteor hammers. This helps the plant to propagate, as the fruits and seeds are carried to faraway places by passing animals.

Special Seed Dispersal

In addition to Rose Mallow, there are quite a few plant species in Hong Kong that adopt such seed propagation, including Shepherd’s Needles (Bidens alba) and Cocklebur (Xanthium sibiricum). These special burrs actually inspired the invention of the magic hook-and-loop fasteners!

Rose Mallow has many uses too. The little flowers are pink like peach flowers, so are named "ground peach blossoms" in Chinese. The strong stem fibres were used to make ropes in the past. The whole plant is of medicinal value and can treat different ailments such as cold, fever, rheumatism and digestive problems.

Next time you are hooked by Rose Mallow, you may try to help it spread by dropping the seeds onto soil before returning to the city!

Text | Karen To

The leaves are of varied shapes; some are round and some are ovate.
The immature fruit is green (top), already covered in fine hairs and hooks. Upon ripening, the fruit turns brown (down), and dry and light-weight, allowing it to easily attach to passing animals.
The little flowers are named "ground peach blossom" for their close resemblance to peach flowers.