Controlling tradescantia

Trad is the weed Tradescantia fluminensis (also known as T. albiflora). While the privets are the most important woody weeds, trad can be a big problem on the forest floor. It covers the ground in a thick mat and prevents the regeneration of rainforest seedlings. It also smothers four Australian native species that are closely-related: Aneilema acuminatum, Aneilema biflorum, Commelina cyanea and Pollia crispata.

Trad doesn't produce seed, at least in Australia. As a result, if you remove the vegetative bits, it doesn't come back unless it's re-introduced, say by floating in on a flood. That said, killing all vegetative bits is difficult, although far from impossible. It's a weed that's worth a bit of study, because it's easier to control if you know just what conditions favour it, and what its weak points are.

Herbicide treatment

Trad grows in damp, shady places as a thick mat. Unless you have vast resources of labour, don't try to hand-weed large areas of such thick monocultures. One effective strategy is to attack the mat in the following stages

• Identify any native seedlings that survive. Rake the trad stems away from them, leaving them within a cleared circle.

• Spray as much of the rest of the trad mat as you can summon energy for, avoiding the native seedlings. Use glyphosate diluted to 6 g/l (~20 ml/l of the 360g/l concentrate). After spraying, it's important to leave the area untouched for 3 - 4 weeks.

• Return after those few weeks armed with a rake, the sort with strong metal tines or, even better, the McLeod tool that's used in bushfire control. Although looking sick, some stems will still retain the potential for regeneration. However, they will be easier to rake back than the original cover was.

• The sick-looking trad is poorly anchored to the ground. Rake it onto the green and lively area that you didn't get round to spraying. Try to rake in different directions so that you catch thick stems that could have survived the herbicide. Again, apart from hand-weeding fragments, leave the area untouched for a further 3 - 4 weeks.

• Return to the area where you dumped the raked trad, now reshooting, and spray again, including another swathe of green trad mat. After 3 - 4 weeks, return to rake it back still further, keeping the raked areas absolutely free of regrowing fragments. Keep going...

Smut fungus

A biological control with the fungus Kordyana braziliensis showing promise has been introduced by CSIRO. Contact Dr Ben Gooden, ben.gooden@csiro.au for information.

Hand weeding

Where trad isn't growing as a thick mat, it can be weeded by hand. Wear gloves (surgical gloves are best for delicate weeding), because trad sap can cause an allergic response. Important points:

• DON'T throw fragments of trad on to a pile of sticks (rafting) because it will thrive there.

• DO segregate the trad from other weeds, as a pile or even better, in a 'corral'. If you then spray the pile with dilute glyphosate (6 g/l), it will rot down and be invaded by the roots of neighbouring trees. Keep coming back to your pile because follow-up is needed when surviving fragments of stem resprout. Glyphosate is not the most lethal herbicide for trad, but has the advantage that it is quickly broken down by bacteria in the soil.

• For effective control by spraying, the trad should be growing vigorously. Treading on it slows its growth and interferes with hand weeding too, because it digs little bits into the soil.

• Be sure to return to the areas that you have sprayed or weeded after a month or two. Tiny fragments that were missed the first time round will reveal themselves by sprouting and these MUST be removed or spot-sprayed.

• Kill trad on your own property. Putting it in the garbage, or worse, throwing it over the back fence, is anti-social. By doing so you spread it around. And, like any weed, trad releases valuable nutrients as it dies and so killing it locally will help your trees to grow.

Controlling trad effectively is very rewarding, especially when you see native ground covers and tree seedlings stimulated to germinate once the mat of weed is removed. All this fuss may sound complicated, but it's a difficult weed that needs a consistent and effective control strategy. This method removes the weed and leaves a soft bare seedbed. Many natives have dormant seeds under the mat of trad and they are stimulated to germinate once it is removed. Euodia (Melicope micrococca) and red ash (Alphitonia excelsa) are just two examples. However, you MUST continue to revisit the area over the following months. This is to hand-weed or point spray bits that have grown from the tiny trad fragments that you are bound to have missed. Alternating hand-weeding with herbicide treatment is more effective than either by themselves. This mother-of-all-weeds demands time, effort and, above all, persistence for control. However, the rewards of success are great. At least, they have been on our site, because native seedlings seem to regenerate especially well in the soft soil from which thick trad has been removed.

The long term method

Trad thrives in partially-shaded, moist and fertile areas - just the kind of places that would, in its absence, regenerate rainforest. But even trad has its limits. It struggles to grow in mature rainforest, especially where a diversity of vines has helped to close the canopy. The mature trees are also highly efficient at taking up nutrients as soon as they are liberated from their fallen leaves. With good management, regenerating rainforest will attain that resilient stage more quickly, shading and starving out this extraordinary weed.