We don’t ordinarily think of orchids as “weeds”, or invasive species capable of establishing viable populations outside of their native range. But among the 18,000 species in the family Orchidaceae, nearly all highly specialized, there are a small number exhibiting weed-like behavior although none causes economic problems as do many weeds. Here are ten species that exhibit weedy tendencies somewhere in the world, primarily in the tropics.
Arundina graminifolia– is seen as an escaped plant that establishes along roadsides in Costa Rica and elsewhere in the tropics. In Hawaii, for example, it is considered an invasive species. It can be grown outdoors as far north as Orlando in central Florida, but is not established in the state except in cultivation. Native to southeast Asia and India and known as the bamboo orchid, stems may reach 3m in height! The plant is self-fertile and produces bulb-like structures along the stem.
Bletilla striata is reported as escaped in moist hammocks of northern Florida and wild plants found in Kentucky and North Carolina. This terrestrial orchid is native to temperate east Asia (China, Japan and Taiwan) and is commonly cultivated.
Cyrtopodium flavum (C. paranaense)- is aggressively colonizing the rare rocky pinelands habitat of Miami-Dade County (southern) Florida. Native to Central and South America, dissemination of this plant is reported to be aided by a non-native bee that serves as a pollinator. It is widely cultivated. The closely related C. punctatum known as the cowhorn orchid because of its large horn-shaped pseudobulbs, may be found as a native epiphyte in far southern Florida growing especially on bald cypress and on buttonwood trees (Conocarpus erecta) in coastal forests near Florida Bay.
Epidendrum radicans – is rare as an escape in Lee County, Florida. Native to Central America and South America, it is common in open areas and exhibits some weedy tendencies in disturbed tropical areas. Often cultivated to display its orange and red flowers, this is a vine-like species with stem roots that enable it to climb walls and other plants. Sometimes given as E. ibaguense.
Epipactis helleborine– introduced from Europe to North America in the mid-1800s. Widely naturalized in northeastern and midwestern U.S., it has reached California and colonized a limited area of Canada. This species establishes in disturbed sites like lawns, gardens and edges of paved areas. Herbicide-resistant, E. helleborine is classified as a noxious weed in Wisconsin. A second species of the genus, E. palustris, is native to Europe and Asia, and is capable of forming large clumps but is much more local in North America than is E. helleborine. E. palustris has been collected in the wild in Pennsylvania and New York but is declining in its native range.
Oeceoclades maculata, is a terrestrial species native to Africa and Madagascar that has become well established throughout the Neotropics and in forested areas of southern Florida such as the hammocks (tropical forest stands) of Everglades National Park. It is reportedly found wild north to Sarasota County.
Phaius tankervilleae- an eastern Asian terrestrial species with a very wide native range. It features broad pleated leaves and large flowers (“nun’s orchid”). It is reported as escaped in Hawaii, Florida, Cuba and Puerto Rico. It flowers abundantly in central Florida (zone 9b) and if grown beneath trees, tolerates the modest freezes that can occur there. Somewhat self-fertile, plants in my yard produce a few developed capsules with seeds (not verified to be fertile) among the many more infertile flowers.
Spathoglottis plicata is considered invasive in Hawaii and the Caribbean islands and is naturalized in parts of Africa. Native to southeast Asia, it is seen mostly as purple-flowered but also occurs as a yellow-flowered form (unclear if this has varietal status). My purchased yellow-flowering plant was labeled as a hybrid, without details. Wild plants apparently can revert to self-fertile status, producing many viable seeds.
Vanilla mexicana – a vining species rare as an escape in Collier and Miami-Dade Counties, Florida in tropical hammocks and cypress swamps. Native to Mexico and Central America, this is perhaps a pre-Columbian introduction into the U. S. Formerly known as V. planifolia, this species is the source of commercial vanilla and therefore has been widely planted in the tropics where it has often escaped and established wild populations. Like most members of the genus, this species is hemiepiphytic (occurs as an epiphytic at first but later becomes rooted to the soil).
Zeuxine strateumatica– a small terrestrial species that is established as an exotic in the Gulf Coast region from Texas to Georgia, mainly in moist lawns and grassy areas. It belongs to a genus of about 80 species none other of which has spread beyond their natural range. A native of Asia including temperate areas such as Iran, China and Afghanistan, this species is also naturalized in Mexico, the West Indies and in California. It was probably introduced as acontaminant in imported centipede grass seed. The species is short-lived and in my yard appears unpredictably in various lawn areas as small clumps of up to a dozen or so individual flowering plants which disappear after a few weeks. Some years it is entirely absent.