WEED OF THE MONTH

JANUARY

Japanese Honeysuckle, Lonicera japonica, is a vigorous evergreen climber which has its origin in Japan, China and Korea. It is a perennial garden favourite, used to cover fences, walls, pergolas, arbours (and crumbling outhouses) which it does with great vigour, rapidly producing a tangle of twining stems. These stems, which can grow to 4.5 metres long, are hairy and purplish when young, but soon become woody. Juvenile leaves are often deeply lobed; the light green more or less oval adult leaves are borne in opposite pairs along the stem. Tube-like fragrant nectar-filled white flowers, which age to yellow, occur in profusion all summer, and are followed by small shiny black berries in autumn.

 
Weedy in the Garden
 
Most gardeners soon find out the true nature of Japanese Honeysuckle. On the positive side, it is attractive, hardy, fast growing and needs little care, producing foliage, flowers and fruit in abundance. In excess, many would say, for it spreads vigorously and intrudes where it is not welcome, becoming invasive without careful control. Its woody twining stems need sturdy support, and if the fence isn't up to it, Japanese Honeysuckle will use anything vertical to get its head in the sun, including one's most prized garden specimens.

Weedy in the Bush

The berries of Japanese Honeysuckle are attractive to birds, including native fruit-eating birds like the Pied Currawong and the Silvereye, and birds play a significant role in the spread of this plant into bushland areas. So too do we humans - far too many people still use the bush verges as convenient dumping grounds for their garden waste. If a plant is a problem in the garden, it will be a even bigger problem in the bush, where the gardener is not around to keep it under control. Japanese Honeysuckle is a perfect case in point: cuttings in contact with the ground will layer (grow roots), and soon a new plant is growing. Once established, Japanese Honeysuckle does not need birds to help it spread: its long stems also layer, sending down roots at the swollen woody leaf nodes.

Japanese Honeysuckle prefers to grow in moist but well-drained fertile areas, especially around creeks and road drains affected by urban runoff. However, like any successful weed it is not too fastidious, and is often found growing on roadsides and at bushland edges, and on disturbed sites - perhaps where the native vegetation has been buried under garden wastes, or where soil from another site may have been introduced.

Here Japanese Honeysuckle has blanketed the vegetation below a road drain in moist forest. Bushcare volunteers removing it have uncovered old waste dumping - and mature tree ferns.

Japanese Honeysuckle can permanently change the character of a bushland site, causing native plant loss, habitat loss, invasion by other weeds.

The Beauty is a Beast

The greatest impact of Japanese Honeysuckle in bushland is on shrubs and low canopy trees, over which it may quickly form a complete blanket, blocking light to the plants which support it. Its sheer weight can cause branch or canopy collapse. Can it kill trees? Yes indeed. The dense growth blocks light to the leaves, and restricts the tree's ability to photosynthesise. The conditions of darkness, warmth, moisture and poor air circulation under the vine can lead to deadly fungal infections of the bark. The tree may eventually die, but not the honeysuckle, which will still be triumphantly holding its head in the sun and continuing its rampant growth.

On this site in Leura, only weeds can compete with the Japanese Honeysuckle, which is supporting itself on the dead skeletons of native trees and shrubs.
 

Prune - or Poison
 
In the home garden it is possible to confine Japanese Honeysuckle by vigorous pruning. Cut back hard after flowering to prevent fruiting. However, this plant responds to any such disturbance by reshooting vigorously, so you may eventually want to do what has to be done to save bushland - remove it.

Large infestations of Japanese Honeysuckle can often be removed by raking and rolling it up like a carpet. Regrowth can be sprayed.

Japanese Honeysuckle can be dug out, but this can be an arduous task, as it will reshoot energetically from any roots left in the ground unless these are poisoned. Poison roots with herbicide using the cut and paint or scrape and paint techniques described on this website, and in the free booklet Weeds of Blue Mountains Bushland.

Go Native!

It is not too difficult to suggest alternatives for Japanese Honeysuckle. A fast growing and showy ornamental creeper that won't go bush is the Potato Vine (Solanum jasminoides), or if you have a sheltered spot, the Chinese Star Jasmine (Trachelospermum jasminoides) gives you a perfumed alternative. But why not go native, and have many more birds come to your garden for their food! A vigorous creeper (many less vigorous cultivars are available) is the Wonga Wonga vine (Pandorea pandorana); somewhat more delicate are the native clematis, Old Man's Beard (Clematis aristata), the Bluebell Creeper (Sollya heterophylla), and the scrambler Purple Twining-pea (Hardenbergia violacea). All are evergreen, and stunningly beautiful in flower. (Keep an eye on the Bluebell Creeper, however: this Western Australian has become weedy in some areas.)