Alien Plants

(Parthenium hysterophorus)

How to identify this plant.

The pretty, soft and frilly leaves form a rosette on the ground when the plant is small.  It is light but bright green in colour.  The little white flowers can form when the plant is very young and then more and more flowers form.  The plant grows to 1,5m and even up to 3m in favourable conditions.  It is an annual plant but can be perennial where winters are mild with a regular supply of water.

Each flower has 5 seeds which become viable when the flower turns brown.  One plant can produce as many as 10 000 seeds.  These remain viable in the ground for up to 20 years.  The seeds are spread by wind, water and animals.  They are also spread by man – on their shoes and in their car tyres.  Seeds germinate easily in disturbed soil although they do germinate in compacted earth as well.  The plant material puts out phytotoxins which inhibit the growth of other plants and in that way it destroys the natural bush.  This is our most dangerous alien invasive plant and it is of national concern.

Parthenium is shallow rooting and can be pulled up easily.  Protective clothing should be used. The pollen emits allergens which cause hay-fever, asthma, allergies and dermatitis. It can be cut and sprayed or cover-sprayed with a suitable herbicide.  All pieces of Parthenium cut or pulled out should be buried in a deep hole or burnt.  According to an article on the internet the following solution can be used to spray Parthenium:  I0 lts Water to 1kg Sea Salt and 1 lt washing up soap or soap oil.  Cover-spray plants well.  Do not spray any indigenous plants as this solution will kill them too.  Bio-control agents have been introduced but it will take some 20 years for them to become effective.  In the meantime it is essential to control this plant in order to save our park.

For more information contact Joce Gordon 082 306 5122 or Terence Porter 0827853429