Weed shrubs and weed trees – the “no dig” option for eradication

Many of us accept the heavy labour of complete eradication of woody weeds by digging. With the arrival of glyphosphate based herbicides (e.g. Roundup or equal) 40 years ago, we can now be much smarter, much kinder to our backs and much kinder to the environment by minimising erosion.

Ochna serrata with new and maturing fruit. Photo: Jacqui Hickson

• Cut, lop or saw through the main stem close to the ground level with a horizontal cut
• Quickly apply neat Roundup to the cut just inside the inner bark to the exposed cambium layer.
• The cambium layer lies next to the conductive tissues, which will transport the herbicide to the growing parts of the weed where cell division is occurring.
• Most woody weeds will be dead in a few weeks.
  
  

This no dig option, called “cut stump and paint”, does not however work on two common woody weeds we find in our gardens. We may in fact have planted them years ago but now learn that they are aggressive environmental weeds – the ochna (or Mickey Mouse Plant) and mature camphor laurel (Cinnamomum camphora).

We will deal with ochna in this issue. It has recently finished flowering and fruit will now be forming. Mature fruit is much enjoyed by Currawongs who readily spread it everywhere.

Ochna No-dig eradication

• Do not attempt to hand pull Ochna. The tap root is roughly spiral and has a hook at the end, causing the tap root to snap off some 10 cm below ground and giving rise to a mass of coppice regrowth a few months later.
• Take your sturdy sharp knife (a butcher’s boning knife or secateurs blade) and scrape the outer bark from 20 cm length of the main stem for a width of about 3mm.
• Immediately paint or smear Roundup (ie. 36% glyphosphate) onto the exposed scrape.
• Cut the main stem with a horizontal cut just above the side branch above the stem scrape and apply herbicide to that cut too.
• Pick off and bag fruit as garbage. Other debris may be added to compost heap.
• Always wear gloves and ensure herbicides are applied a minimum of four hours before rain