Environmental weeds: Trying for ivy control - and how many berries does it take to grow a bush?

During June-September, many berries have been cut off non-Australian bushy shrubs in this area, both in our garden and out in the native bushland and parkland where I help on the Landcare teams. So many bushes of privet, cotoneaster, briar rose, hawthorn, with so many hundreds of berries.

It made me think - why aren't there hundreds of seedlings of these shrubs springing up all over the place, having sprouted from the berries dropped by the bush and by birds?

Perhaps the reason is that a large proportion of berries are eaten and digested before the seeds in them can germinate. In her blog* in July this year, Rosemary (Mt Rogers Landcare Coordinator) writes that she watched silvereyes (small native birds) and mice eating cotoneaster berries. I've noted before that native parrots (crimson rosellas) and currawongs (native raven-type birds) almost queue up to eat the berries - for example, there were five currawongs one day, taking turns on the last bunches of privet in our garden! One can assume that some berries will be collected by insects such as ants - except that ants don't come out very much, if at all, in the cold winters we have here in Canberra.

Anyway, I've decided to do some tests. I've reserved bunches of privet berries and handfuls of cotoneaster berries from our own garden bushes, stored them on the back step in the normal weather, and today (11 September 2011) I've set them into shallow trenches, covered them with soil and watered them.

My idea is to see if seedlings emerge - in a mass, or just a few - and how long it takes. This is a very rough test, and if anything grows I intend to do a more scientific assessment next year.

Ivy is another pest plant that is rampaging - in a creeping sort of way - across the garden here. Like everyone else, I want to find a way to control it, so I've set up two tests so far. The first was simply to strip the growth off a gate post where it was so well established it had grown berries! The stripping took place in mid-winter, when the ivy was probably not growing fast. In the same few days, I also began the second test: thoroughly spraying the leaves of ground ivy with Roundup (proprietary herbicide) and then immediately (within a minute or two) covering the sprayed leaves with a thin layer of mulch.

The results of the stripping are encouraging. (They are a repeat of my experience in another garden where I just pulled the ivy out and off the side of the house, and also pulled out any regrowth later. Excellent control.) Only one stem of ivy remains on the gate post (it was inaccessible to my stripping in July-August), and it has a few new shoots on it now, as we move into spring.  Provided I hook that stem out soon somehow, I expect that growth to come under control easily.

The results of the spraying and covering are negative. The mulch has been breached in a few places by big ivy leaves, and where I pull the mulch back to look beneath it, there is healthy ivy waiting to burst through. However, grasses and other weeds that were sprayed along with the ivy are very dead.

The next test will be to apply two sprays: first a detergent solution, using the detergent from the kitchen for dishes, followed quickly afterwards with a spray of Roundup. It'll be important not to make the leaves too wet with the detergent. The detergent is supposed to break through the waxy coating on the leaves so the Roundup can penetrate into the plant tissue. But if the leaves get too wet the Roundup spray will probably just run off.

When attacking woody weeds in bushland, the Landcare teams work in pairs: one person clears around the stem of a weedy shrub, and then, when the other person with the Roundup bottle is ready, they cut the stem and 'dab' it with Roundup within seconds. That method works very well and should work for ivy - but imagine having to dab every small ivy stem! I've heard that for ground ivy you can run the mower over it and then spray (with a drop or two of detergent in the spray bottle). But again I think that needs to be a 2-person job, with one mowing and one spraying within seconds of the mower passing.

If ivy was coming into our garden through a fence or some similar barrier from a neighbour, where the fence acted as a sort of filter, it should be manageable to cut a small cluster of stems and spray them within seconds with Roundup (again with detergent added).

If successful, that could be a drawback to neighbourly relations. Roundup is supposed to kill the plant right down to the roots. So I might achieve the ivy-control I wanted but lose the friendship of my neighbour - assuming she liked to have ivy growing on her side of the fence. Tricky!

For the rest of the rampaging ivy here, I plan to pull it up and then watch for and pull out the regrowth. It should be a simple and effective way to get this weed under control this spring.

*www.mtrogerslandcare.blogspot.com