To successfully manage weeds, pests or diseases they must be correctly identified. Misidentification leads to incorrect control practices which is costly and often making the problem worse.

Many people still rely on common names of weeds for their identification, however this leads to problems because many species have multiple common names. Some names are only used within some states or even districts such as Fallopia convolvulus which is known as climbing buckwheat in Queensland and black bindweed in New South Wales. A more interesting example is Conyza sumatrensis which is normally called tall fleabane in most places. However, on the north coast of New South Wales it is often known as cobbler’s pegs. Cobbler’s pegs are actually Bidens pilosa which look totally different.
Originally the naming of plants and animals was based on where they came from. For example, any animal from the sea was called a fish. This included whales and dolphins. Many Australian plants were given English names because the colonisers had a European world view. For example, the tallest flowering tree in the world – Eucalyptus regnans – was called mountain ash. It looks nothing like European ashes (Fraxinus spp.).
Our modern naming system of genus and species comes from Carl Linnaeus (1707-1778) who divided flowering plants into groups depending on their flowers and fruits.
Unfortunately identifying plants by flowers and fruits is too late for most management strategies. Therefore, it is good to use vegetative characteristics to identify plants. This has the major benefits of early weed identification which are cost effective allowing timely management strategies to be implemented.
Starting point for identification

Land plants are divided into groups of increasing complexity in structure, particularly the vascular tissue and how they reproduce and spread. It is generally accepted that land plants commence with green algae and goes through to the flowering plants.

  • Green algae – contain chlorophyll, no roots or vascular tissue.
  • Mosses & liverworts – have absorbing organs, not roots
  • Club mosses – single veins in small leaves, and union of stem and leaf without a break in the vascular tissue of the stem. Reproduce by spores.
  • Horsetails – hollow, jointed stems, reproduce by spores and have an extensive root system
  • Ferns – highly dissected leaves which unroll from the tip, reproduce by spores and often have rhizomes
  • Gymnosperms – seeds borne upon scales in a cone or as a naked seed – cycads, ginkgo, conifers
  • Angiosperms – flowering plants – seeds enclosed in a seed case or ovary – monocotyledons and dicotyledons

The starting point to narrow down and identify the majority of weeds (flowering plants) is to figure out whether they are monocotyledons or dicotyledons. It is all also handy to know over half of weeds come from 5 families of flowering plants – Asteraceae, Brassicaceae, Fabaceae, Poaceae (monocot) and Iridaceae (monocot).
Monocotyledons can be identified by the following characteristics:

  • plants are herbaceous (no woody parts)
  • single seed leaves
  • leaves lack a leaf stalk, with each leaf consisting of an upper strap-like blade and a sheathing base that encloses the stem
  • ligule on the upper leaf surface is membranous or hairy
  • leaf veins are parallel with no single main vein
  • roots are fibrous
  • includes the major families Poaceae, Liliaceae, Cyperaceae, Orchidaceae, Iridaceae, Amaryllidaceae and Alliaceae

Dicotyledons:

  • 2 seed leaves (cotyledons)
  • Shoot system consisting of:
    -main axis (stem)
    -leaves attach to the stem at nodes
    -each leaf consists of lamina, leaf stalk (petiole) and strongly developed main vein with lateral veins (reticulate)
    -buds in leaf axils and at the end of stem
  • Root system – primary or tap root, with lateral roots

Plant – environment associations

Knowing the types of env