July: weeds

Why are weeds a major threat?

Weeds by nature are vigorous and invasive. They will pop up and take over your site whether you want them or not. This creates a battle ground between your revegetation plants and the nasty invaders. They compete for water, nutrients and space until one wins and the other meets its demise. So before we start planting we need to remove the intruders.

Who is the “goodie” and who is the “baddie”?

Now what is considered a nasty plant varies from region to region depending on environmental conditions. An example is moth plant (Araujia hortorum) which is a climber that looks very similar to the edible choko but is highly toxic. In Auckland you will see the seed pods dangling from trees in most urban areas in late summer. However in Christchurch there are none to be seen due to the cold conditions. The best place to find out what weeds are the biggest issue in your region is to check out your local council’s website. Auckland Council has a great guide in their biosecurity section (click here). Focus on eradicating the environmental weeds or those with the potential to smother your plants. The biggest “baddie” for this in Auckland is kikuyu.

To spray or not to spray kikuyu?

The most efficient way to deal to Kikuyu is to spray it off. There are many pro’s and con’s to using chemical sprays, with countless heated discussions between horticulturalists as to its use. They are great for doing large areas, in a short time period, at a low cost. On the flip side using herbicides will kill off wanted plants too, such as any native seedlings that are popping up on their own. In addition, it destroys the soil biota as the existing bacteria and fungus depend on their relationships with the plants – which were killed by the glyphosate spray. Once off applications will limit the detrimental effects, so once your plants are of a side to overcome smothering, let the plants shade out the weeds. For kikuyu, it has deep diving rhizomes and expansive surface cover, so an initial spray will get down to the roots, then the odd follow up to deal to the rebel survivors, is my plan off attack.

Weeds 2 kikuyu

How big are your muscles?

Sometimes time and a touch muscle power will get rid of your weed problem. There is nothing like going back to basics and heading out with your spade or other weeding tools and pulling out a few weeds. Another option is to smother the weeds themselves using black matting or a mulch. One tricky darling I have to get removed is a hulking great crack willow right on the edge of the stream. Crack willow reproduce through branches being swept downstream in floods to become lodged in banks where they put out roots, creating groves of new plants. For this plant I am getting a tree removal company to safely cut it down and grind out the stump. I will then monitor the stretch of stream for any saplings that pop up. On a side note, willow mulch is great for the garden, it breaks down quickly to release nutrients in to the soil, and I might even put some down around my revegetation plants that are out of the flood zone.

Next blog I will cover creating a planting plan. Finally putting all our research and ruminating into action.