Nurseries explore new uses for drones, from inventory to scouting to spray treatment

Initially a tool for the military and aviation hobbyists, unmanned aerial systems — better known as drones — have a wide range of applications. Filmmakers, search and rescue, farmers and ranchers, surveyors, even archeologists find uses for them.

Will the nursery industry be next?

So far, adoption has been slow, but J. Frank Schmidt & Son Co. in Boring, Oregon, started looking at ways to undertake inventory from above as far back as the mid-2000s. They performed an experiment using a helium balloon with a camera attached.

“It was a total failure,” said Sam Doane, production horticulturist and drone advocate who has been in charge of experimentation and use at the nursery. “It was a crazy idea, but it got people excited about going forward with drones. We try it and if it doesn’t work, we keep on trying.”

In 2010, a few years after the balloon fiasco, Doane worked with Joe Mari Maja, now an assistant professor at Clemson University, and James Robbins, a now-retired Extension specialist and professor at the University of Arkansas. Mari Maja built the drone and the group did the first demonstration. Schmidt needed a more efficient way to count 6 million trees that grow on hundreds of miles of fields — from Boring to the Bay Area, they like to say. Robbins and Mari Maja, both well-known in the drone world, wanted to experiment.

They flew a drone above the trees taking photos. The photos were transferred to a computer and software “read” the photos and “stitched” them together for an overall view. At least, that’s what it was supposed to do.

“Software didn’t exist then to capture large areas,” Doane said. “We set points on the ground and programmed the drone with GPS to fly from point to point. We had to do the math of where we wanted the drone to fly and how much overlay was needed between images. We literally held a ruler up to the monitor and drew points to figure out how to do it. It was very exploratory.”

Scouting, counting and more

Software, and everything about drones, has changed since then. Drones can be an exciting — and labor-saving — tool for the nursery industry. Together, a drone, camera and software setup can estimate the number of trees per acre; gauge the height of nursery stock; and assess the health of field-grown trees by identifying areas of poor soil conditions, disease, die-off, and moisture problems.

A study by Michigan State University, working with Remote Sensing and GIS Research and Outreach Service in 2017, involved flying over Christmas tree and arborvitae fields. The studies showed when the drone flew within 200 feet above the Christmas trees, the inventory was over 97% accurate. The heights of the arborvitaes were accurate to within 4 inches.

Before committing to drones, however, any business must be aware of Federal Aviation Administration (FAA) regulations. To fly a drone, the operator must be certified by taking a test biennially. If the drone is over 55 pounds, a special license is required when flying in the “gray zone” near airports, and a special waiver is needed.

Some people find the requirements onerous, but Brian Scott, department chair of the School of Agricultural Sciences at Mt. San Antonio College in Walnut, Califorinia, sees it both ways.

“There are two camps,” he said. “One side wants to move as fast as it can. Pilots and the FAA want to regulate it and slow it down. We need to be safe but need progress moving forward. I’m somewhere in the middle.”

Kristine Buckland, Oregon State University (OSU) Extension Service vegetable and seed crops specialist and assistant professor in the College of Agricultural Sciences, said it’s not difficult to get a license. Local airports usually have the training and there’s a class through OSU’s Professional and Continuing Education program.

“You can get a license with no problem,” said Buckland, who has been researching the use of drones in agriculture since 2018. “The FAA has training documents on its website. You have to spend time learning about airspace. You can take the test at your local FAA testing center. I’ve seen people go through it no problem. It’s not a big obstacle.”

There are two types of drones: multi-rotor, which have more than one motor, are the easiest and usually the cheapest; and fixed-wing drones, which fly faster and are lighter, so they don’t use as much battery power.

Multi-rotor drones hover like helicopters to offer more control — an advantage when taking photos or streaming video. However, they take more energy to stay in the sky. They can get to places fixed-wing drones can’t. The more rotors, the heavier the drone is and the more batteries needed to keep it up for any length of time, usually topping out at 40 minutes, maybe 60 in excellent conditions.

Fixed-wing drones fly faster and are lighter, so they don’t use as much battery power. They glide through the sky, similar to an airplane. This type of drone only needs the energy to move forward and not to hold itself in the air, making it energy efficient. They can stay in the sky longer, depending on weight, but can be expensive.

Most commercially used drones feature high-performance cameras offering impressive quality. They range from familiar SLR (single lens reflex) still or video cameras to photogrammetry. Cameras using photogrammetry take photos from different angles and piece them together like a puzzle to create 3D photos, according to Jay Perez, professor of photography and drone technology at Mt. San Antonio College in Walnut, Califorinia.

“We can take flat photos and make them 3D,” Perez said. “We can see how high is that tree. As soon as you mass that data, you can use it in so many ways. It’s the future.”

Spotting the symptoms

Scott often goes to Perez with a problem he thinks a drone might solve in less time than people on the ground — things like early detection of diseases and pests. For instance, they’ve used drones to search for areas of sudden oak death and problems on golf courses. It’s easily transferable to nursery stock.

Drones don’t uncover which disease or pest is present, but show the symptomology, Scott noted. For example, if plants are off-color, more than likely there’s something wrong. Is fertility off? Not enough moisture in the soil? Disease? Once the photos indicate a problem, workers can go out in the exact area of the field and examine the plants. With rising labor costs and worker shortages, it makes sense to look from above rather than walking row by row inspecting trees.

There is one problem for some nurseries. If they grow a lot of plants with a variety of foliage colors, drones will show possible problems that aren’t really problems, said Doane of J. Frank Schmidt and Son.

“The biggest limitation is the whole index is based on green is healthy,” he said. “We don’t live in a world of green. We have chartreuse, blue, variegated. Some will show up as unhealthy when they aren’t.”

That’s when operators switch to multi-spectral cameras that use multi-colored infrared wavebands to capture both visible and invisible images of crops and vegetation. But that’s expensive, Doane noted.

A grower can spend anywhere from $1,500 to $30,000 or more on a drone, which includes all its necessary accessories. The price also depends on how big it is, how much it weighs and what type of add-ons are included, such as the camera, sensors and batteries. The bigger the drone, the bigger the battery it needs, and the less time it can spend in the air. J. Frank Schmidt spent $8,000 on its drone and $2,000 on the battery, which has to be replaced every few years.

At OSU, a grant bought them a robust system that costs $8,000–$10,000 for the drone and $10,000–$15,000 for each camera. And technology is moving very fast, Buckland said. A new camera has almost twice the resolution of their current one, a significant improvement. The higher the resolution, the better the ability to capture images that tell the story of the crop on the ground.

Investment vs. return

Scott of Mt. San Antonio College is somewhat skeptical that drones will save money at the present time, but admits if a nursery saves 10%–20% in labor, that’s significant.

“In an industry where you have a lot of plants, that percentage is a big deal,” he said. “You pay up front but in the long run it will eventually start saving you a lot of money.”

Buckland of OSU agreed. “How much can you save?” she said. “You can calculate it the easy way or the more truthful way. It’s not just about going out to the field and flying over it. You have to learn how to do it, you’ve got to figure in the time and money. There’s the set up and you’ve got to learn the software. Maybe you scout the field in a third of the time and spend another hour with the software. Theoretically, you can detect before the human eye can and intervene earlier so you wouldn’t have the yield damage, the loss or the cosmetic damage. That’s the idea, but to get to that point, it takes a long time.”

However, Buckland admits, “I feel like the crop value is so high in nurseries that I can agree it’s a good investment. No one is going to buy a plant that doesn’t look good.”

For smaller nurseries and even some larger ones, it makes more sense to hire someone to fly the skies above your property, gathering valuable information.

Marion Ag Service, Inc., in St. Paul, Oregon, takes it a step further, said Anne Iskra, technical services manager for the company. They fly drones to troubleshoot problems for customers and then consult on how to solve them. They use a large fixed-wing drone with a 3-foot wingspan. It takes off vertically and flies like an airplane for 45 minutes on one battery.

In another application for drones, Homeland Surveillance & Electronics, a company in Casselberry, Florida, deals in spraying fields with pesticides and sells, leases, trains, and maintains drones for those who want to do it themselves. According to Bryan Sanders, president of the company, it’s a precise job that relies on the correct nozzles, which has sprayed over 1 million acres in 18 countries fighting pests, diseases, and weeds.

“For us it’s all about the science,” said Sanders, who anticipates expanding his business into the nursery industry. “It doesn’t matter how great the drone is. If the nozzle isn’t the right size, if it can’t put out enough chemical but not too much that it causes drift, then who cares how great the drone is?” 

The drones are programmed by the operator, who hits a button and the drone lifts off and goes to the end of the row, then slides over to the next row and flies back to the beginning and does it over and over. It takes minutes rather than hours — usually 20 acres in an hour — cutting down on labor and adding efficiency.

“On the ground people have to walk between rows, wearing PPE and it’s 80 or 90 degrees,” Sanders said. “They get burned out, so accuracy and consistency on every plant goes downhill after a couple of hours. They’re exhausted. No one wants to do it. With a drone, no one has to put on PPE and walk for hours and hours and hours.”

But everyone can agree on one thing.

“Drones are part of the future,” Iskra said. “I don’t know if they’ll completely replace what boots on the ground can do, but they definitely enhance it.”

Kym Pokorny is a garden writer with more than 20 years’ experience writing for The Oregonian (Portland, Oregon) and other publications. She is currently a communications specialist with Oregon State University Extension Service.