College of Florida hemp mission addresses environmental impacts

US farmers now want to grow legal marijuana cousin

Hemp legalization is pushing U.S. farmers into uncharted territory, luring them with profits amid the turmoil in agriculture, while proving to be tricky in the early stages (November 21).


The University of Florida’s Institute of Food and Agricultural Sciences completed a two-year pilot study measuring hemp growing opportunities in Florida.

The project aimed to assess the suitability of hemp, develop management strategies, and assess the risk of invasion in Florida. The university monitored 50 different hemp varieties in the field and in the greenhouse.

Zachary Brym, an assistant professor of agronomy at UF and lead scientist for a hemp pilot project, said researchers have not yet been able to identify a strain that would thrive successfully in Florida’s climate.

Hot and humid conditions, amounts of summer rain, and the length of the days can hinder hemp growing in Florida.

“We don’t have any recommendation or information with any particular one (that could thrive), but we’ve found several candidates,” said Brym. “We were able to identify a number of challenges.”

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Risk of invasion

Some of these challenges can be controlled by growing indoors with greenhouses, which also helps address potential problems with the invasiveness of hemp.

Hemp produces many small seeds that can be spread by birds, wind, or other weather conditions. If hemp fields are not carefully tended, the plant has the potential to spread to unwanted areas.

“Hemp is one of those classic examples of a potentially invasive species, so to speak,” said Brym. “It still has many so-called wild-type traits … We have seen in some of our controlled studies that hemp has escaped cultivation, so the risk of invasion is still something we want to be wary of.”

Hemp also poses some threat to the environment as it requires fertilizer. Fertilizer promotes algal blooms and nutrient pollution, which can contribute to the red tide in the region’s waters.

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Research for the pilot program doesn’t have all the answers about the effects of hemp fertilizer on the environment, but Brym says this is something he’s particularly interested in as the program expands.

The researchers will study how much fertilizer each hectare of hemp needs and what amount does the least damage while producing the best hemp product.

“We encourage everyone to be aware of what they are applying and to be conservative when applying so that we don’t get caught up in this subject where there is too much and which is detrimental to the environment,” said Brym.

Legal Limits

There are also legal concerns for farmers who choose to grow hemp.

According to the U.S. Department of Agriculture, hemp must stay below a THC limit of 0.3%. Plants that exceed this amount must be destroyed. The problem is that a farmer has no way of knowing if a particular batch exceeds the allotted THC limit. That makes growing hemp pretty risky.

Brym admits that some of the university’s tests crossed the state line.

“They know you can have all of the makings for a really strong hemp plant in the field, but then you send it in for testing and it exceeds that 0.3%,” Brym said. “Then you won’t get anything out of the field, except a whole lot of grief.”

Right now, Brym doesn’t see that growing hemp in Florida is making the money people can hope for.

“Right now there are more economic challenges,” said Brym. “It’s expensive to buy the seeds and plant material, it’s a lot of work, and so anyone interested in buying hemp just to make money really has to think about these kinds of problems.”