Miconia calvescens, known to Hawaiian locals as the “green cancer” or “purple plague,” first came to the Hawaiian Islands in the 1960s as an ornamental plant for botanical gardens. Since its introduction, miconia has spread extensively through Maui, Big Island, and Oahu, causing major ecological damage wherever it invades. The South American plant can grow to heights of 50 ft and has large purple and green leaves. According to the HNIS Report for Miconia calvescens, the plant flowers and fruits simultaneously, usually several times each year. Miconia’s fruits are small, but they each can contain 50 to 200 seeds. It is estimated that mature trees can produce up to three million seeds each time they fruit. Non-native birds, such as the silvereye and red-vented bulbul, disperse the seeds far across the island when they consume the sweet fruit. Seeds may also spread via contaminated mud stuck to shoes, clothes, or vehicles. The seeds that fall from the trees accumulate in the soil, creating dense seeds banks that can remain dormant for years.

The Department of Land and Natural Resources of Hawaii warns Hawaiians of the dangers of miconia takeover with examples from Tahiti, which was also overrun with the plant. By the 1980s, miconia had invaded over 60 percent of the land. Currently, over a quarter of Tahiti’s native species are threatened with extinction as a direct result of the miconia invasion. Because the Hawaiian Islands are similar to Tahiti in climate and environment, miconia poses an equally large threat to Hawaiian ecosystems.

Miconia causes many problems for the ecosystem it has invaded. According to the Hawaiian Invasive Species Council, Miconia is on the Hawaiian State Noxious Weed List and has been designated one of Hawaii’s Most Invasive Horticultural Plants. It can harm the natural ecosystem in several ways. Miconia’s enormous leaves create large amounts of shade, killing all native species that require heavy sunlight for survival. Miconia also causes problems with erosion because its roots are not as deep as the roots of the native plants. As a result, there is less to hold the soil in place, which, in some cases, causes massive landslides, further harming the native ecosystem.

The film “Strange Days on Planet Earth” opens its segment on the Hawaiian miconia invasion with dramatic images of the massive amounts of erosion on the island. The film then shows the plant in the wild and gives background on the situation. Even more than the effects of myconia on the ecosystem, the film emphasizes the eradication efforts Hawaiians have taken against miconia.  The film shows high-tech removal operations that use aerial photography to find populations of miconia that are inaccessible by foot.  Those populations are then sprayed with an herbicide. People have also been uprooting the plants manually. However, miconia’s seeds, which fall into the soil in large quantities, pose a large problem to both eradication methods. Because they are difficult to kill with pesticides and can remain dormant for up to ten years, the populations of miconia must be monitored for years after the original plants are killed. New sprouts that spread their own seeds could reverse all of the previous eradication efforts. Removing the plants completely would require constant vigilance for several years. Five years after the film “Strange Days on Planet Earth” was filmed, it would be interesting to see if the eradication methods shown in the film were effective.



One Response to “Miconia: the Purple Plague”

  1.   Michael Potts Says:

    It is amazing how devastating a simple tree can be, especially an aesthetically-pleasing one at that. I had not known that a single fruiting cycle from one tree could produce as many as three million seeds. That seems such an overwhelming number that eradication or containment methods almost seem pointless. However, I am sure that a large portion of those seeds do not reach fertile ground or die. Also, the fact that these seeds can lie dormant for years could pose an alarming problem. Where on Hawaii’s Big Island or across the pacific might myconia infestations be lying in wait? In addition to knowing if the eradication methods discussed in the movie have been effective, would it also not be interesting to know if more research has been done on the myconia plant to discover possible alternative methods of containment or eradication? Or even if myconia has spread to other Hawaiian islands through the beaks of birds?

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