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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-relatedAneilema acuminatum, Aneilema biflorumCommelina 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...
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.  

weeding tradescantia

This is a trad 'corral', where hand-weeded or raked trad can be dumped. Then, you MUST return to spray with glyphosate herbicide every few months to ensure that it rots down. On a floodable site like this one the corral needs to be supported by some substantial stakes. Otherwise it would be swept away when the flood plain becomes a lake. In between floods, it's sufficient to rake trad into piles for spraying, although brush turkeys and lyrebirds can be a problem. They will rake through the rotting trad for insects, scattering it in the process. Even worse, turkeys may incorporate it in their nest mound, where fragments are likely to regrow. Corrals aren't very pretty, but they can help to overcome these problems.

Before you kill it, have a close look at a trad flower. Those white hairs among the stamens are a window into the life of a plant cell. Under the microscope (photo below), the hairs are seen to be strings of cells, so transparent that you can see mitochondria streaming along strands of protoplasm. 
Photo Michael Reid
You can see protoplasmic streaming (cyclosisin this video - worth a visit to see how lively those floral hairs of tradescantia are. The tiny black specks streaming along the strands of protoplasm are mitochondria, the powerhouses of plant and animal cells.

Our trad is sterile
Don't worry if you see trad flowering, because it won't set seed. This is because it was introduced into Australia as a self-sterile clone. There is always the danger that another clone could arrive to pollinate and set seed with our resident one. 
If that happened to us, that would make trad an even more serious weed.  

More information can be found from the following link:
The potential for biocontrol of trad is being investigated in New Zealand. Three beetle species from SE Brazil, where trad is a native plant, appear to show promise. One of these eats the foliage (Neolema ogloblini), another the growing tips (Neolema abbreviata), while yet another eats the stems (Lema basicostata).

Fun method of weed control

A hand spray can be used like a water pistol, so that isolated trad fragments growing in hard-to-get places can be targeted. If you hit a native plant, just wash it with a jet of water - in other words, carry two hand sprays, one with water and one with herbicide (coloured, so as not to mix them up).

It's amazing how your skill at hitting weeds in inaccessible places improves with practice. Don't forget the water though. It's a pain to have fetch it on a hot day when you accidentally hit an endangered native plant!

This method can be adapted to encourage single native seedlings within a dense mat of privet seedlings. Just spray the lot, and immediately wash the native with squirts of water. Come back to see the result after three weeks!