Species Orchid Society of
Western Australia (Inc)
It grows like a weed
How often have you heard the phrase "It
grows like a weed!" Most often this expression means that the plant
that is vigorous and easy to grow. But, conversely, a 'weed' is not something
that we want in our orchid pots. However, a 'weed' is just a plant that
is in the wrong place. It is not of itself a nuisance other than when
it is out of its natural habitat where nature provides checks and balances
in the form of predators, climatic conditions or soil types that restrict
Patterson's Curse or as it is known in South Australia, Salvation Jane, Echium plantagineum , native to western and southern Europe (found from southern England south to Iberia and east to the Crimea), northern Africa, and southwestern Asia (east to Georgia) was introduced to Australia, South Africa and United States. It is now an invasive weed, and due to the high concentration of pyrrolizidine alkaloids in the shoot, it is poisonous to grazing livestock, especially those with a simple digestive system like horses. The toxins are cumulative in the liver, and death can result. It also blocks up cereal harvesting machinery.
There are many other examples of plants that have become
weeds when introduced to an environment where they do not occur naturally.
So it begs the questions, can this happen with orchids? In general, orchidaceae
tend not to be weeds because they are highly adapted to their
The WA Department of Agriculture and Food has a list
of 'known weedy species'. There are two orchids on this list, Oeceoclades
maculata and Spiranthes sinensis. While import of these species
is prohibited, I was not able to find any information about local infestations
are other orchids which also have the potential to become weeds. Perhaps
the best known local example is a South African orchid Monadenia bracteata
(recently reclassified as Disa bracteata). This species apparently
made its way to Australia on ships from South Africa in the 18th century
and is now widespread in southwest WA and Victoria. While it is not a
proclaimed species (a noxious weed) in either WA or Victoria, it has been
identified as a new and emerging weed in the Wimmera district as it is
considered to be a threat to the environment as it has the
A local example with which some of you may be familiar with is Cynorkis fastigiata from Comoro Islands, Mauritius, Madagascar, Reunion, and the Seychelles. This species turned up in plants brought in from the Eastern States in the media. A vigorous terrestrial species, it is readily pollinated by local insects, with wind-dispersed seed. Some years ago, many of us had this species growing in other orchid pots although I suspect that it is no longer a problem as we destroyed unwanted tubers when we repotted our plants.
In the United States, the broad-leaved Helleborine (Epipactis helleborine) is now causing serous concern as it becomes established in garden beds and lawns.
It was intentionally introduced from Europe and is now spreading throughout Michigan in lawns, flower beds and along driveways. This orchid's (syn Serapias helleborine) natural habitat is Europe and Africa through to China.
The Michigan State University has had many samples submitted by homeowners for identification and advice on removal.
Unfortunately (though an advantage to plants that become weeds), this orchid is also very vigorous, and will regrow from even small segments of root left in the ground.
However, in a somewhat strange twist to this story,
Epipactis helleborine is now
Arundina graminifolia (syn Arundina bambusaefolia) also known as Kinata weed is an Asian terrestrial species that has shown potential to become a serious weed. This species has now colonised many new habitats including Hawaii (where we saw it on the big island in the Kilauea national park), Cook Islands, Guam, Fiji and Marshal Islands as well as Puerto Rico, Jamaica and Guadeloupe. It is very adaptable and rapidly takes over roadsides and any similarly cleared areas, crowding out local plant species. It is very vigorous and keikis from just below the raceme after flowering. It is not particular about its pollinators, and as a result, it is cited as invasive in many Pacific islands,
In a paper by Ms M Goosem on issues associated with
control of weeds along major powerline routes in Queensland, she strongly
recommends that a localised infestation of Arundina
In an article by Clifford and Kobayashi 2012, Naturalizing Orchids and the Hawaii Pacific Weed Risk Assessment System, the authors identify several exotic introduced orchid species that in their view pose a serious weed risk to Hawaii. These include Arundina graminifolia, Spathoglottis plicata, and Vanda tricolor. A major concern is the displacement of native plants that can occur through crowding out.