PAPER MULBERRY:
 A WORSE WEED THAN CAMPHOR LAUREL?

Published in The Nimbin Good Times. May 2004.

Nimbin Plant Selection Guide

David McMinn


In the mid 1980’s, I purchased several attractive plants called paper mulberry (Broussonetia papyrifera) at the Channon Market. I was into permaculture and self sufficiency at the time and liked the idea of being able to utilise the bark of the trees to make tapa clothe (produced by the Polynesians). Rather stupid in hindsight. The trees were planted out around our property at Blue Knob, north of Nimbin. Twenty years later, I am having a major poisoning campaign to eliminate this noxious pest from our farm and surrounding properties. Not only do birds relish the fruit and disperse the seed widely, but it also has a profuse suckering habit – up to 35 metres from the main trunks – making this a very nasty weed. Plant a tree and you have a suckering forest in a decade. It may also be distributed by flood waters, which flush cuttings downstream to establish new groves kilometres away. The trees at Blue Knob are currently being killed off, involving much time and effort. There is a window of opportunity to eradicate it from the Nimbin valley. Once it becomes firmly established, it will be extremely difficult to control and impossible to eliminate. 

The tree is most obvious in early winter, as the leaves yellow and fall to the ground. During the growing season, the adult tree is easily distinguished by its large, rounded leaves, which make it stand out against the backdrop of other species.  The leaves on young plants are highly ornamental as shown. Young plants of paper mulberry and the common black mulberry look similar and may cause some confusion. However, the black mulberry never suckers and its the leaves are glossy. The big questions are Who else was so silly as to plant this species? and Are there other specimens of this species in the Northern Rivers region? If you see this tree growing on your property, it is imperative that you get rid of it quickly before it becomes an enormous environmental problem.

Mature trees may be killed by using Access herbicide (17 ml per litre of diesel). This is painted to encircle the base of the trunk, when the tree is actively growing. Small suckers may be killed by spot spraying using glyphophosphate (Round Up). Several applications will be necessary to finally get rid of all the suckers. Totally impractical to get rid of by organic methods (mechanical), due to paper mulberry’s very profuse suckering habit.  

The scenario I have had with paper mulberry is all too familiar. Planting attractive exotics and, then several years later, having to poison the adults and pull out the seedlings when they start getting out of control. I have repeated the same mistake with numerous other species.

Apple mint (Mentha rotundifolia). The last big drought finally got rid of this pest in my garden.

Coral Tree (Erythrina crista-galli). Spreading along our creek from properties further upstream.

Cocos Palm (Syragus romanzoffianum). Still being sold and planted in the region.

Coffee (Coffee arabica). It took four years to pull out the last seedling from our garden.

Golden Trumpet Tree (Tabebuia chrysotricha). Sets profuse crop of seedlings every year.

Ice Cream Bean (Inga species). Still sold at the markets even though its weed status is now well known.

Tung Oil
(Aleurites fordii). I am still pulling out seedlings in my rainforest gully.

Goldenrain Tree
(Koelreuteria paniculate). Widely planted in Lismore as a street tree. Sets a profuse crop of seedlings every year.

If you must plant potential weeds, there may be ways around the problem. A seedless form of Orange Jessamine (Murraya paniculata) is available, so people can still enjoy the perfumed flowers without causing a weed problem in the local rainforests. (Birds eat the fruit of this species and spread the species widely.) Even better, plant the equivalent native species (Murraya ovatifoliolata) so the birds can enjoy the fruit and you the scented flowers. Curry leaf (Murraya koenigi) is another weed candidate, as it suckers prolifically and birds like eating the fruit. However, it can be placed in a large container and the green, unripe fruit stripped from the tree every year. For species with male and female flowers on separate plants, only plant male specimens may be used in the garden, so the seedling problem is completely avoided. A local palm enthusiast planted Chamaedorea palms in the rainforest near his house. After a few years there were numerous palm seedings popping up along the creek. He poisoned the female plants and pulled out the seedlings, leaving only the male plants. He can still enjoy his palms, with no adverse environmental impact.

The nursery people must accept much of the blame for the current parlous situation. They introduce the latest new wonder plant, make a some money and then the local forests and land owners are saddled with a huge weed infestation. Millions of dollars are spent each year spraying herbicides, which contaminate the food chain and wreck the environment.

Every gardener in the Northern Rivers has to be responsible in their plantings. Another 50 years and the region will be filled with weeds and our wonderful natural environment severely degraded. These days I plant mainly native rainforest species (especially those native to the Northern Rivers) and those exotics that I do grow must be verified as being non-weedy. Pity I was not warned about the weed issue in the 1980’s, when I first arrived in the valley. Quite frankly, it is a waste of time, money and herbicide, when something more sensible could have been planted in the first place.


Copyright. 2004. David McMinn. All rights reserved.