This article is submitted by Jeremy Croudace, a veteran of many a hacking expedition, who has done much to restore invasive alien infested hillsides to the original pristine splendour of the Cape floral kingdom. He is the author of the excellent handbook for effective hacking entitled, ” The Alien Clearing Handbook for the Western Cape.” If you would like a copy, contact him at croudace@adept.co.za We believe that Jeremy is correct – there is no quick fix for eradicating this highly successful species. Slow methodical clearing is by far the best.

Photo: J. Croudace

This photo shows one of the strategies that make Port Jackson a nemesis for many a prospective alien clearer and helps to explain why it is such a successful invader. It also illustrates the main reason why follow up costs on the same plants can far exceed the cost of the initial clearing.

The plant in the picture has been burned, which has removed most of the main stem and triggers the same response as cutting, i.e. it coppices the plant and changes its growth form from a small tree with a trunk to a many-stemmed bush.

The crucial area at the base of the stem, extending about 30 mm above and below ground level is called the bud bank. It is from this ‘collar’ of bark, immune to cutting, browsing and fire that a seemingly inexhaustible reserve of dormant stem buds can sprout. Any attempt to kill a Port Jackson outright is most likely to be successful when the bud bank is directly targeted.

The best option is to remove it altogether. Small plants can be pulled out, if the ground is soft enough. Port Jackson has a deep taproot and an irritating way of breaking off at the first node above the bud bank, a survival mechanism against heavy browsing.

Loppers can be used to cut the taproot below the bud bank at about 40mm below ground level which, is indicated in the picture by the point at which the stems turn from green to white. The taproot then mercifully, dies and gradually rots, unless it is exposed to sunlight soon enough, in which case in a nasty twist on the vampire myth it can come back to life and send out new shoots. Follow up costs should be below ten percent of initial clearing if the job has been done properly. Excluding fire and disturbance which, bring new seedlings into the picture, subsequent timely follow-ups should have less and less to deal with.

Here’s the method:

Push the closed blade of the loppers diagonally into the ground feeling for the taproot at the right depth below the bud bank and clearing a space either side of it. Doing this job with an open blade damages the cutting edge. Only when the space is cleared and the obstructing stones pushed away should the blade be opened and the taproot cut. If rootlets remain attached to the end of the plant, when it is pulled up, you have an indication of success and it is easy to monitor.

Stump peeling is an effective way of killing saplings and young trees too big for the lopper method. Port Jackson has a fairly short life span if left undisturbed, about twenty-five years. In the last few years of its life it develops a rough flaky bark. At this stage the bud bank seems to close down and undamaged rough barked stumps seldom re-sprout when sawn cleanly. Regular coppicing extends the life of Port Jackson.

Stump peeling also targets the bud bank, inflicting mortal damage to the area of the bark most capable of producing stem re-growth. Bark peels easily in strips off a young Port Jackson stump freshly cut at a height of 30cm. The purpose of cutting at that height is to provide for a comfortable length of bark to hold on to. All side branches should be removed from the stump. The idea is to strip the bark away from the wood, pulling outwards all the way down to a point below the bud bank and then tear it off. A few taps with the back of the saw will loosen the bark at the place where the peeling gets underway. Pink spongy inner bark, as opposed to the normal pale green and fibrous is an indication, that bud bank has been stripped away. Rootlets near the end of the 20mm wide strip, is another indication of success. Anything wider, by the way, requires a lot more strength to tear off and the effort is difficult to sustain over long periods. Don’t leave any bark in situ.

This method, properly executed is deadly effective on single stemmed trees, as well as those with a small number of stems. Within a year or two the whited rotted stumps can be kicked out of the ground – a pointless but extremely satisfying thing to do.

Stump peeling, though effective, is time consuming and prone to inefficient execution. Workers need to be well trained. Unfortunately far too much emphasis has been (and continues to be) put on the speed (and therefore cost) of initial clearing. Little regard is paid to the capabilities of the bud bank or of killing the plants outright. The long-term cost implications for the follow-ups and therefore the sustainability of the eradication efforts also seems to be ignored. The result is follow up costs that exceed and over time cumulatively dwarf the initial clearing costs- on the same plants! Little wonder that alien clearing is seen as a bottomless pit and funding is often in short supply!

Treating stumps with herbicide saves time and can be effective provided a few rules are followed.

• Saw the stump as close to the ground as possible, preferably through the bud bank itself. Thicker pinkish bark is the indicator.
• Apply the recommended herbicide immediately, concentrating on the bark. Initially sap drops in the stump when the leaves, which help draw it upward through transpiration, are cut away with the rest of the plant. Use this phenomenon to draw the herbicide deep into the bud bank. Later the stump may start to ‘weep’ as water taken in by the roots backs up. This limits penetration by the herbicide. Later still the cut dries and the stump becomes impermeable rendering herbicide application pointless at that stage.
• Mind the environment! Most other plants are more vulnerable to herbicide than Port Jackson is. Apply it directly to the target stump. Don’t slop or spray it around!

The most daunting challenge Port Jackson can present to the alien clearer (killer) is the toughened old multi- stemmed survivor of many previously unsuccessful attempts on its life by hacking, fire and foliar herbicide spray. If a Port Jackson has been coppiced repeatedly the bud bank swells to form a ‘crown’ from which a scratchy tangle of dead and living stems protrude making it hell to work with and very hard to kill. Sometimes if the ground is soft enough it is worth getting at the taproot and sawing it off if too thick for loppers. Otherwise a rather tiresome process lies in store.

• Remember before you start that you never, ever want to have go through this process on this plant, again. Deadly intention is very important!
• Using loppers and a saw cut back all the stems as close to the bud bank as possible. Don’t worry if you damage the swollen bud bank for that is the whole idea.
• Using the back of the bush saw or whatever else is suitable bash and bruise as much of the bud bank bark as you can get at. If bits flake off so much the better.
• Immediately apply herbicide and hope that does the trick.
• It may not. Such a plant has a large store of carbohydrates and may still re-sprout a few more times but must not be allowed to re-grow. Persistent timely persecution is necessary to prevent it regaining strength. Pull off new shoots while they are still soft and follow with an immediate dose of herbicide to the wounds. It will soon expire.

Accustomed to adverse conditions, Port Jackson has evolved a formidable range of other survival mechanisms including rapid growth, hardiness to drought and the prolific production of seeds capable of long dormancy in the soil. While these factors have a major bearing on the task facing the alien clearer, none is as significant to progress in the eradication efforts as the bud bank and its capability of producing countless stem buds.

Past experience should have taught us by now that the ‘blitzkrieg’ approach of mass annihilation does not work on Port Jackson. It’s too tough and resilient to succumb to such an un- focussed assault. Alien infestations consist of numerous individuals that each requires individual attention to kill. What is needed against Port Jackson is a programme of relentless ‘ethnic cleansing’. There is no silver bullet, no magic weapon.

Photo: Steve Coe

The rust fungus, Uromycladium tepperianum was introduced amid high expectations that it would be such a silver bullet and for years stands of Port Jackson were spared clearing efforts so that the fungus could reproduce. On the whole over time the results have been disappointing; few individuals have died and most bear their ugly galls with little ill effect. Indeed they often outgrow them, stranding the orange galls in the lower branches. Seed production has not been significantly reduced.

The choice is simple – continue making grand but futile gestures, whenever funding is available, by quickly clearing large areas of Port Jackson (thus promoting coppicing) or take the slower and much more certain approach outlined above and emphasised by the maxim, “maximum fatality at first encounter”.

Submitted by Jeremy Croudace (slightly edited – administrator)