SIOUX CITY — An iconic plant, whose leaves have seven or more slender points, grows unbidden in the crevices between sidewalks and retaining walls, in ditches, near fences and alleyways, along railroad tracks, in poorly maintained landscapes, in state parks and nearly every other place where the grass grows green.
It’s colloquially known as “ditch weed,” or feral cannabis, wild hemp and variations. Thereon, it’s a not a particularly uncommon sight in Siouxland or most other places in the Midwest.
“I see it throughout the day, here and there,” Woodbury County Weed Commissioner Jered Jepsen said.
Feral cannabis plants grow in the crevice between a sidewalk and a retaining wall along West First Street in Sioux City.
But where did it come from — and why is there so much of it?
Most ditch weed is descended from hemp, a cannabis plant and very close relative of marijuana, but which contains far less psychoactive THC. Cannabis is not native to the Americas. Hemp was likely brought here by Europeans, years before the Pilgrims landed at Plymouth Rock.
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Hemp was cultivated historically to make rope, sailcloth and twine, mainly in Kentucky (where it was introduced in 1775) and in Wisconsin. By 1910, a limited degree of industrial hemp cultivation was underway in Iowa, Nebraska, Minnesota and in several other states.
High times
The presence of ditch weed in Iowa is primarily attributable to World War II, when the American economy frantically transitioned to a war-footing. Hemp became a government-sanctioned “war crop.” In a December 1942 bulletin, the Iowa Agricultural Extension Service and the Iowa Agricultural Experiment Station wrote that farmers in northcentral Iowa were asked to plant at least 60,000 acres of hemp. Iowa was one of several states that took part in the effort.
(That same bulletin also cautioned, in the imprecise verbiage of the time, that “parts of the growing hemp plant contain a narcotic substance known as ‘marihuana (sic).’”)
Two hemp-processing mills operated in Iowa then, though the government in 1942 wanted at least 15 hemp-mills in the state.
“That’s when most of the production here in Iowa was,” said Bob Hartzler, a retired professor of weed science at Iowa State University.
“Japan took over the Philippines, and that’s where we got all our fiber crops, and so that’s why they started producing (hemp),” he added.
Ditch weed is shown growing along the hiking trail that leads to the First Bride's Grave in Sioux City.
The experiment in Iowa production of hemp fiber didn’t last long. Iowa farmers, characteristically, produced a bountiful crop of hemp, but the farmers produced more than was actually needed, Hartzler said, and the program was de-emphasized. It was the only occasion prior to the late 2010s when Iowa farmers engaged in intensive, widespread hemp cultivation.
Before the World War II hemp boom, the federal government restricted cannabis cultivation with the Marihuana Tax Act of 1937. The wartime emergency prompted the government to briefly encourage hemp cultivation, but, after the war, hemp as a crop vanished.
By then, however, hemp had already been introduced, and in the form of ditch weed, it proved quite capable of succeeding in the wild. Hemp emerges earlier than other weeds, giving it an advantage, and it can tolerate drought and heat, Hartzler said. The female hemp plant can produce “a lot of seed,” he added.
And so it became more or less ubiquitous.
Not for human consumption — usually
But not every single ditch weed plant is necessarily descended from long-ago hemp cultivation. One study published in the American Journal of Botany in 2020 found that 88 percent of ditch weed samples in Minnesota were descended from hemp-type plants with minimal THC content, while 1 percent was marijuana with a correspondingly high THC content. The remaining 11 percent of plants were “intermediate,” with THC levels that didn’t correspond perfectly to either modern, high-THC marijuana strains or low-THC hemp.
Robin D. Pruisner, a state entomologist, hemp administrator and ag security coordinator with the Iowa Department of Agriculture and Land Stewardship, said those intermediate-type plants with some THC content, but not all that much, could plausibly be descended from long-ago marijuana cultivation.
“If you went to Woodstock, in 1969, or you partook in the ‘70s, marijuana at that time had much lower THC than what has been bred in what I’m going to call the ‘recreational states’ now,” Pruisner said.
Ditch weed is shown growing along the hiking trail that leads to the First Bride's Grave in Sioux City.
The consensus is that ditch weed is not normally desirable for human consumption.
“It’s not the weed that people want,” Jepsen said. “You know, the people who use marijuana. It’s not the same stuff.”
The state of Iowa does not regard wild hemp as a “noxious weed” — weeds which are considered environmentally problematic or harmful to animals or humans, and which by law must be controlled and killed.
The only occasion when Jepsen sprays herbicides to kill ditch weed in the county, he said, is when it’s growing near an intersection, in a place where it could obstruct drivers’ lines of sight. Cannabis can, under the right conditions, grow to be much taller than humans.
“More than anything, it’s an eyesore,” Jepsen said. “And it grows in a lot of places. It’s throughout Woodbury County.”
Feral cannabis plants grow in the crevice between a sidewalk and a retaining wall along West First Street in Sioux City.
It’s not particularly hard to kill. Ditch weed was once a common sight growing randomly in and around crop fields in Iowa, Hartzler said — until the introduction of corn and soybeans that could withstand glyphosate herbicide.
“In the ‘80s and early ‘90s it would creep into crop fields, and I would say it was never a big problem, but you’d find it on fence edges,” Hartzler said. “Then with the introduction of Roundup Ready crops in the late ‘90s, it didn’t stand a chance against that.”
Jepsen said he fields occasional calls about ditch weed — oddly enough, some callers are worried that it could have a negative impact on hemp crops they’re considering planting. But, he said, since it isn’t really the policy of the county or the state to spend resources eradicating ditch weed, there isn’t much he can do for them.
“I’ve already been contacted by a few people in Woodbury County that have thought about trying to grow it, you know, for the oil, and they were worried about it cross-pollinating with the Iowa ditch weed,” he said.
‘Sort of a boondoggle’
The legal status of hemp in the United States changed with the passage of the 2018 Farm Bill, which paved the way for regulated production of hemp. Initially, Iowa farmers were in a flurry of excitement about the new crop — but, as was the case in 1942 and 1943, the production prowess of Iowa farmers turned out to be more than the market could bear.
“It was sort of a boondoggle,” Hartzler said. “A lot of people lost a lot of money trying to do it.”
The high-water mark for modern-day hemp cultivation was in 2019, when the amount of hemp grown was more than 500 percent higher than it was the year before, Pruisner said.
“But, our consumer demand, our processing capacity, did not increase at that same rate,” she said. Some of the hemp products and cannabis extracts from that bumper 2019 crop, she added, “is still sitting in warehouses and clogging the market up.”
Ditch weed is shown growing along the hiking trail that leads to the First Bride's Grave in Sioux City.
The number of licenses to grow hemp in Iowa, and the number of acres of hemp under cultivation, declined precipitously after 2019, according to data from the Iowa Department of Agriculture and Land Stewardship. In 2020, there were 86 hemp licenses issued and 680 acres of hemp under cultivation.
By 2022, there were only 32 licenses and 99 hemp acres — significantly less than a single quarter-section of farmland growing hemp in the entire state.
While ditch weed is not, in and of itself, illegal, attempts by unlicensed individuals to privately harvest and keep it on hand could be interpreted as possession of a controlled substance (in theory at least; in practical terms, the lines have blurred quite a bit since the 2018 Farm Bill, and hemp products are sold quite openly in stores).
“In my weed science classes, I required students to make a weed collection, and I’d always say, ‘It’s OK if you want to include wild hemp in your weed collection, but if you get arrested, I’m not going to bail you out, and if I get arrested, you’re going to fail the course,’” Hartzler said with a chuckle.