2015 Widespread-Thoroughly Distributed-North America
100 Most Widespread and Most Thoroughly Distributed Species

North America View (2015)


That the two most widespread North American vascular plant species, Taraxacum officinale and Capsella bursa-pastoris happen to be exotic, might concern some natural historians, weed specialists, plant ecologist, or others who believe that our native flora needs protection against all exotic invaders. Many thousands of scholarly papers have been written over the past several decades about the success of exotics, and their expansion into new locations around the globe, but nowhere more than in North America has a continental flora been so profoundly impacted by a greater percentage of exotics. Considering that half of the thirty most widespread species in North America are exotic, and slightly more than 20% of the entire vascular flora of North America is exotic (!), how is it possible that a native flora of nearly 19,000 species has become so infiltrated by exotics, nearly all of which are relatively recent arrivals. One reason is that many exotics are more successful at reproducing and dispersing than some of our native species. Another is that they arrived preadapted to the habitats we created for them through the alteration of pre-European North American landscapes.

Centuries ago, when the earliest foreign mariners faced the hardships of oceanic travel, some of the more courageous and fortunate ones successfully sailed and landed their vessels along a primitive North American shoreline, and knowingly or unknowingly, successfully introduced the first exotic plants. It is reported that at least some of these early travelers brought with them seed sacks filled with foreign grains. Unfortunately, these sacks of seeds were also laden with contaminated seeds and spores of other foreign species as well. As part of their cargo, they also carried dried roots and various plant parts, and in some cases live plants. At least some of the exotics that they brought happened to be prolific seed producers and able to disperse their seeds widely and rapidly across the landscape.

To a lesser degree, natural phenomena can also be blamed for its role in dispersing exotics. The vortices of cyclones, typhoons, hurricanes and even tornadoes can blow seeds and spores thousands of miles to and from landmasses around the globe. Rafting events too have been shown to be a source of species introductions, but these sources pale by comparison to the thousands of exotics introduced accidentally or deliberately into North America through agricultural and horticultural practices; which then begs the question, are all these exotics really that bad? A common theme that has penetrated the moral fiber of conservationists' protocol throughout the U.S. is to avoid exotics at all cost. In fact, for the past few decades, their clarion call has been to plant native species in lieu of exotics throughout the U.S.

In opposition, is an increasing number of individuals and institutions who are challenging this prohibition. A preponderance of plant enthusiasts do not believe that exotics are bad. In fact, many believe profoundly that the North American flora has benefited greatly from exotics. They argue passionately; what would our grocery shelves look like without exotic fruits, vegetables, or spices? How boring and colorless would our roadsides and pastures be without species like colt's foot, chicory, narrow-leaf cat-tail, sweet clover, Canadian horseweed, purple loosestrife, Queen Anne's lace, oxeye daisy, moth mullein, bull thistle, common dandelion, morning glories, and sow thistles? What would our lawns look like without exotic clovers, blue grasses, crab grasses, rye grasses; or our shrub borders look like without forsythias, lilacs, privets and bamboos to adorn them? And how drab would our botanical gardens, home gardens, and other manicured landscapes be without the displays of daffodils, tulips, peonies, pansies, poppies or hundreds of others handsome exotics? Many of these exotics are mentioned here, because they are included within The Hundred Most Thoroughly Distributed Species in North America; and arguably, in some cases, neither their beauty nor their societal benefits can be duplicated or replicated by native species alone!

Beyond the benefits mentioned above, many exotics add color and beauty to the artists' canvas, as much as they do for increasing species diversity itself. Neither can be duplicated solely by native plants. For those who have studied fine floral paintings of great artists such as Monet's Blue Water Lilies, or his Lilacs in a Vase; or Georgia O'Keefe’s Oriental Poppies; or Judith Leyster's Tulip; or Albrecht Dürer’s Tuft of Cowslips; or Jan Brueghel the Elder's, Flowers in a Vase; or certainly Vincent van Gogh's, Vase of Roses, know and understand the beauty that exotic species provide, and the appeal they bring to human society.

Conversely, plant enthusiasts who visit gardens that specialize in native species exclusively are generally disappointed by what they see as colorless, simplistic, boring and uninspiring. To compensate, some native gardens have introduced regional or national natives via seeds or living plants, in some cases from hundreds of miles away. These same gardens, however, prevent many beautiful plants indigenous to islands less than 90 miles away in the Caribbean from growing in their gardens. So what is the difference between plants introduced from a hundred miles away, several hundred miles away, or several thousand miles away?

Except for the relatively few highly invasive exotics that replace our native species and come to dominate associated habitats, proponents of exotics champion and promote the inclusion of exotics into our flora for all of the reasons stated above. BONAP would like to know your view. -JTK


North America View of 100 Most Widespread and Most Thoroughly Distributed Species (2015) 
rank 001 Taraxacum officinale
rank 002 Capsella bursa-pastoris
rank 003 Achillea millefolium
rank 004 Polygonum aviculare
rank 005 Melilotus officinalis
rank 006 Erigeron canadensis
rank 007 Rumex crispus
rank 008 Chenopodium album
rank 009 Veronica peregrina
rank 010 Typha latifolia
rank 011 Persicaria lapathifolia
rank 012 Vulpia octoflora
rank 013 Xanthium strumarium
rank 014 Echinochloa crus-galli
rank 015 Lactuca serriola
rank 016 Sonchus asper
rank 017 Bromus arvensis
rank 018 Eleocharis palustris
rank 019 Lolium perenne
rank 020 Poa annua
rank 021 Medicago lupulina
rank 022 Trifolium repens
rank 023 Rorippa palustris
rank 024 Setaria viridis
rank 025 Apocynum cannabinum
rank 026 Cicuta maculata
rank 027 Galium aparine
rank 028 Acer negundo
rank 029 Eragrostis cilianensis
rank 030 Populus deltoides
rank 031 Prunella vulgaris
rank 032 Parietaria pensylvanica
rank 033 Bromus tectorum
rank 034Verbascum thapsus
rank 035 Helianthus annuus
rank 036 Medicago sativa
rank 037 Equisetum hyemale
rank 038 Descurainia pinnata
rank 039 Panicum capillare
rank 040 Ceratophyllum demersum
rank 041 Persicaria maculosa
rank 042 Sphenopholis obtusata
rank 043 Schoenoplectus tabernaemontani
rank 044 Persicaria amphibia
rank 045 Solanum rostratum
rank 046 Echinochloa muricata
rank 047 Schoenoplectus pungens
rank 048 Portulaca oleracea
rank 049 Dichanthelium acuminatum
rank 050 Setaria pumila
rank 051 Silene antirrhina
rank 052 Bidens frondosa
rank 053 Digitaria sanguinalis
rank 054 Ambrosia artemisiifolia
rank 055 Comandra umbellata
rank 056 Symphyotrichum lanceolatum
rank 057 Lycopus americanus
rank 058 Nasturtium officinale
rank 059 Stellaria media
rank 060 Poa pratensis
rank 061 Eleocharis acicularis
rank 062 Lepidium densiflorum
rank 063 Dactylis glomerata
rank 064 Trifolium pratense
rank 065 Fragaria virginiana
rank 066 Galium triflorum
rank 067 Plantago lanceolata
rank 068 Amaranthus albus
rank 069 Thlaspi arvense
rank 070 Plantago major
rank 071 Juncus bufonius
rank 072 Rumex acetosella
rank 073 Agrostis stolonifera
rank 074 Phleum pratense
rank 075 Cerastium fontanum
rank 076 Leucanthemum vulgare
rank 077 Sisymbrium altissimum
rank 078 Poa compressa
rank 079 Artemisia ludoviciana
rank 080 Glyceria striata
rank 081 Amaranthus retroflexus
rank 082 Cirsium vulgare
rank 083 Fallopia convolvulus
rank 084 Convolvulus arvensis
rank 085 Sambucus nigra
rank 086 Eragrostis pectinacea
rank 087 Leersia oryzoides
rank 088 Rhus aromatica
rank 089 Maianthemum racemosum
rank 090 Pteridium aquilinum
rank 091 Lepidium virginicum
rank 092 Robinia pseudoacacia
rank 093 Juncus tenuis
rank 094 Triodanis perfoliata
rank 095 Ambrosia trifida
rank 096 Calystegia sepium
rank 097 Mollugo verticillata
rank 098 Daucus carota
rank 099 Teucrium canadense
rank 100 Botrypus virginianus

Last updated June 8, 2015.