A plant native to Eurasia was recorded in North America in 1827, likely introduced through a ballast dump in Massachusetts.
asserted
plant → record → Massachusetts
Known as leafy spurge (Euphorbia esula), the species later spread across the northern United States and southern Canada.
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species → know → States
According to the United States Department of Agriculture (USDA), several introductions may have occurred, while contaminated crop seeds helped the plant establish in new areas.
uncertain
plant → accord → areas
Its extensive root system and ability to reproduce from both seeds and roots help it persist and spread in a range of habitats over time.
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it → reproduce → time
How leafy spurge first arrived in North America
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spurge → arrive → America
The first US collection of leafy spurge was made in 1827 in Newbury, Massachusetts.
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collection → make → Newbury
The plant was thought to have originated from a ballast dump, although the review says there were likely multiple introductions into North America.
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review → think → America
A review cited by the Forest Service suggests at least four possible early introductions.
uncertain
review → cite → introductions
The first Canadian collection was recorded in 1899 in Huron County, Ontario.
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collection → record → County
The species was brought by Russian immigrants in contaminated spelt from Germany.
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species → bring → Germany
Early spread was also linked to the planting and cultivation of contaminated smooth brome and cereal seed originating both inside and outside North America.
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spread → link → America
These records point to several possible routes by which the plant became established across the continent over time.
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plant → point → time
Leafy spurge became widespread across North America by the early 1900s
By the early 1900s, leafy spurge was widespread in the northern United States and southern Canada.
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spurge → become → States
It had been recorded in Ontario by 1889 and Iowa by 1899.
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It → record → 1899
Around 1900, it was described as naturalised in parts of the northeastern United States, while reports also placed it in Oregon and Washington.
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reports → describe → Oregon
It was recorded in Idaho in the early 1900s.
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It → record → 1900s
The Forest Service identifies Oregon, Idaho, Montana, Wyoming, Colorado, North Dakota, South Dakota, Nebraska, Minnesota, and Wisconsin among the states where leafy spurge is most widespread and invasive.
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spurge → identify → states
In western Canada, it occurs as far north as Yukon.
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it → occur → Yukon
How did leafy spurge spread through roots and seeds
Leafy spurge is an erect perennial plant that usually grows between 20 and 90 centimetres tall.
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that → spread → roots
Its narrow leaves grow along the stems, while leaves near the flower clusters are heart-shaped.
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leaves → grow → clusters
When the stems are damaged, they release a milky fluid.
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they → damage → fluid
The plant produces small seed capsules that split explosively when mature, ejecting seeds.
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that → produce → seeds
It also regenerates from its root crown, root buds, and root fragments.
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It → regenerate → crown
Its persistent root system can be deep and extensive, allowing shoots to emerge even after above-ground growth has been damaged.
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growth → allow → ground
The species grows in roadsides, old fields, pastures, meadows, areas beside rivers, and open woodlands.
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species → grow → rivers
It can establish in disturbed sites and persist in many habitats.
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It → establish → habitats
How did leafy spurge affect native plants and grazing animals
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spurge → affect → plants
The Forest Service describes leafy spurge as a highly invasive plant that can establish in stable, undisturbed native plant communities.
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that → describe → communities
Its rapid vegetative spread and dense stands can replace native or rare plants.
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spread → replace → plants
Thick layers of plant litter may prevent light-demanding species from establishing, while other research discussed in the review suggests that the plant may also affect neighbouring vegetation through chemicals and changes to soil conditions.
uncertain
plant → prevent → conditions
Leafy spurge is avoided by cattle and horses when other forage is available, and its milky sap can cause severe diarrhoea in both animals.
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sap → avoid → animals
Control is difficult because roots can survive after above-ground growth is removed.
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growth → survive → ground
Sheep, goats and introduced insects, including flea beetles, have been used to reduce its abundance.
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Sheep → introduce → abundance
The Aporia
