Flowering heads of Euphorbia esula
Euphorbia esula, commonly known as leafy spurge or wolf’s milk, is a herbaceous perennial native to temperate areas of Europe and Asia, where it can be found in dry meadows, stream banks and sandy areas. At maturity, leafy spurge is typically 20-90 cm (to 3 ft.) tall.
Leafy spurge can be recognized by its glabrous, oblong to lanceolate leaves, Euphorbia-type inflorescences, and dense, clump-forming habit. The alternately-arranged leaves on the main stems can reach 8 cm (to ~3 in.) in length and 1cm (~0.5 in.) in width, and the leaves nearest the base of the plant have shortened petioles. Euphorbia esula blooms continuously from mid-spring to early autumn. The inflorescences are umbels, with each cluster of insect-pollinated flowers containing a single pistillate flower and 12-15 staminate flowers. The thusly-incomplete flowers lack both sepals and petals. Pairs of heart-shaped bracts, each 12-16 mm (0.5 in.) in length, cup individual flowers in the inflorescence.
Euphorbia esula was introduced to North America in the early 1800s, likely by means of contaminated crop seed. On this continent, this invasive species can now be found growing in grasslands, shrublands, riparian areas, dry roadsides, disturbed areas including burn sites, floodplains, prairies, stream banks, and big sagebrush communities. It most commonly occurs in the western and central parts of the United States and Canada, and less frequently on the coasts. In Canada, leafy spurge has been ranked sixth out of eighty-one invasive species most detrimental to natural habitats (see: Catling and Mitrow. 2005. A prioritized list of the invasive alien plants of natural habitats in Canada. (PDF) Canadian Botanical Association Bulletin). It is listed as a noxious weed or invasive species in 21 states, and even quarantined in Washington and Oregon. Reasons for the plant’s success as an invader include its hardiness over many habitat types, extensive root systems, seed dispersal mechanisms, resistance to fire and herbicide, and toxicity to wildlife.
The major means of spread is by root system, which both spreads widely (radiating outward 0.2-3m (to 10 ft.) per year) and penetrates deeply (up to 9m (30 ft.) below ground (PDF)). Live pieces of root can regenerate to form whole plants when conditions are favourable. This deep root system is also the key to leafy spurge’s fire tolerance, as the above-ground part of the plant alone is burned while the root system remains intact. Leafy spurge then easily grows back from the roots, thriving in the absence of post-fire competitors.
Several hundred tiny brown seeds are produced in three-chambered fruits from mid-spring to the first frost. Under warm and dry conditions, the mature capsules explode, sending seeds up to 4.5 meters (15 ft.) away from the parent plant. Seeds are also dispersed by water and by certain animals, including sheep, goats, and mourning doves.
Leafy spurge seedlings also emerge earlier in the year than the seedlings of most native herbaceous plants. Growing quickly, they outcompete and shade out seedlings of the native flora. The tenacious seedlings become capable of vegetative regeneration within one week of emergence, and are supported by roots that have been reported to reach up to 61cm (2 ft.) deep in less than two weeks following the appearance of cotyledons.
All parts of the plant produce a milky sap containing ingenol–an irritant to humans, horses, cattle, and wildlife. This sap can cause blistering and dermatitis externally, while ingestion has been known to cause inflammation of the mouth and throat as well as abdominal pain. The leaves may have allelopathic properties, as studies show that areas with large amounts of Euphorbia esula leaf litter have reduced plant biodiversity in comparison to other areas.
The above properties make leafy spurge particularly noxious and difficult to control. Chemical control has proven to be both difficult and expensive as the leaves are coated with a protective wax that prevents aqueous chemicals from easily entering them, while the roots possess a mechanism that prevents large uptake of unwanted soil chemicals. Herbicides can also negatively impact native plants surrounding leafy spurge populations. On a small scale, sheep and goats have been used to clear patches of the plant. With some success, six types of Eurasian insects have been introduced to Canada and the United States as a means of biological control of leafy spurge. In general, it is recommended that leafy spurge be placed under an integrated control program involving biocontrol, chemical control, and re-establishment prevention.
Oh my goodness… This one sounds like it will give horsetail and blackberries a run for their money : (
The ingenol gives my wife a reaction not unlike how I react to poison ivy. I definitely had to curtail my collection of genus. I am usually OK sticking with the species that resemble cacti, but have to steer clear of planting more herbaceous species in the yard. I, on the other hand, pull the Gopher Spurge, along with the smaller, weedy Euphorbia,with abandon and have never noticed an adverse effect. I suppose if it got on more delicate skin I might, but I will be wearing gloves in the future to avoid sensitizing myself.
Hard to believe that something that looks so lovely could be so bad. That colour lime just brightens up the darkest shade.
Leafy Spurge is a Provincially listed Noxious Weed under the BC Weed Control Act and an Invasive Plant Species under the Forest & Range Practices Act. In several areas of BC, these non-native invasive plant populations are controlled by biocontrol agents (click my name for website link).
Please report any sightings of Euphorbia esula in BC through the Report-A-Weed or Report-Invasives-BC free apps downloadable through: http://reportaweedbc.ca/
Thanks Judith! This photo of Wayne’s was from 2010, I think, so perhaps that population has already been addressed.
What a nightmare.
Based on the photo all by itself, I am waiting for someone to ask, “Where can I buy it for my garden?” Haha.
FYI my first time( back a few decades) with a euphorbia; I picked a few types to add to my flower arrangements. I touched my face without washing my hands first. Hours later my face had swollen up removing any creases of age around the mouth and eyes. I always wondered if it was safe enough to use cosmetically to remove wrinkles. Anyone have any suggestions?
Pat,
Years ago I went to visit my 88-year old grandmother in the hospital following total hip surgery. For as long as I had known her her face was deeply furrowed with wrinkles. Amazingly, she looked 40 years old and not a wrinkle to be seen. Of course I was not an RN yet at that time and I did not know that she was in fluid overload and her very life was critically in danger. Incompetent staff had allowed several liter IV bags to run in quickly. It filled out her wrinkles nicely but also filled her lungs and caused pneumonia. Beauty can be had but at some dear prices.
Madeline, thanks for that prioritized list of invasives in natural habitats in Canada. I’ve added it to our forums’ http://forums.botanicalgarden.ubc.ca/resources/plants-conservation-resource-links.25/ page.
I have one of these that I grew from seed from the UK (I’m in NYC) and it’s extremely well-behaved and hasn’t tried to take over my 8 x 10-foot plot in the three or more years it’s been there. The Brits have better manners?
Very often an introduced plant will seem stable. After establishing itself–the negative qualities express themselves.
I have Schisandra sp. in an isolated area that after 10 years is an aggressive garden bully.
The same happened with a Campsis radicans. The Campsis required all parts to be dug out. Parts of the remaining root system now grow under a terramac parking lot 20 meters away and it sprouts through the cracks.
The same happened with a Mentha sp. that was supposed to be non-spreading. In 5 years it infested 50 sq meters-growing up through crowns of woody shrubs.
The internet is good for checking potential plants for these qualities. Even the older good garden books lack the warning seen above.
Spurge hawkmoth (Hyles euphorbiae (Linnaeus, 1758)), is one of the biocontrol organisms used. A pretty caterpillar, and also an attractive moth. I remember being sent on a collecting mission in 1979 when I was a summer student at AgCan in Ottawa, working for the Biocontrol Lab. We were mailing out some caterpillars to somewhere else that wanted to establish them.
Strangely, I don’t remember being warned about the ingenol, much less being issued with latex gloves or anything else!
https://en.wikipedia.org/wiki/Hyles_euphorbiae