The science of the season

Michigan State University researchers are helping keep the holiday season green and fragrant by dedicating their expertise year-round to Michigan’s flourishing Christmas tree and chestnut industries.

Chestnuts roasting on an open fire

MSU’s chestnut research program, launched in the early 1990s, includes a multidisciplinary team of faculty, including Daniel Guyer, a professor of biosystems and agricultural engineering in the College of Engineering and the College of Agriculture and Natural Resources, and Mario Mandujano, a research associate in CANR’s Department of Plant, Soil and Microbial Sciences, who are developing new ways to keep chestnuts growing and flourishing in Michigan.

Instead of growing chestnut trees from seed, one programming effort uses plant tissue cultures to grow multiple clonal chestnut plants from a single parent plant selected for their desirable genetic traits, giving researchers control and consistency over the genetic variables of the plant.

While researchers and growers desire certain characteristics, consumers also want specific qualities from their chestnuts. Some prefer smaller chestnuts that are about an inch or less in size,  while others want the large Colossal chestnuts that can grow as large as 2 inches in diameter. Consumers and restaurants want chestnuts that are easy to peel and taste sweet. “Some people think the smaller chestnuts are sweeter,” he said. “But we think the chestnuts, after curing in cold storage, eventually have similar taste and sugar content."

Another issue with chestnuts is storing them. They should be treated more like produce than like traditional nuts, such as dry as they are a living respiring commodity. They should be stored between 28 and 30 degrees Fahrenheit, Mandujano said. If you keep chestnuts cold and in an air-tight container to minimize moisture loss, it is possible they can last three to four months.

That means you can enjoy fresh chestnuts well past the holiday season. 

Oh, Christmas tree

Like chestnuts, Christmas trees also have a long history as a research subject at MSU. Bert Cregg, a professor of horticulture and forestry in CANR, has been conducting Christmas tree research for the past 21 years. Cregg specializes in tree physiology, nutrition and coning. Unlike crops planted and harvested in the same year, Christmas trees are a waiting game that take up to a decade from seed to cutting.

 

“We help farmers manage their crops, and they can maximize their efficiency by not putting out fertilizer they don’t need,” Cregg said. “Farmers are good stewards and try to be as sustainable and environmentally friendly as possible.”

Coning, or the excess production of cones, on Frasier fir trees is another issue Cregg is working on. “Frasier firs produce a lot of cones at an early age and the growers have to pick them off by hand,” he said. “A 9-foot tree could have up to a thousand cones.” 

Interfering with the tree’s hormone cycle can reduce tree coning by half, Cregg said. Also, applying organic herbicides that break down the cone’s waxy cuticles cause them to dry and fall off.

Cregg also is looking at other tree species from around the world to find trees with desirable traits such as vivid green color, smell and needle retention.“We are looking at the Turkish and Trojan fir from northern Turkey,” he said. “I’m not sure it is going to be a winner in Michigan because one problem we are already seeing is late frost damage.”

Robert Goodwin, a senior geospatial analyst with Remote Sensing and Geographic Information Systems at MSU, and colleagues Nicholas Weil and Joseph Welsh, are measuring the health and height of Christmas trees using drones programmed to fly more than 150 feet above the ground.

Back at the office, special software stitches these images together to form both a surface model and mosaic of the tree farm that looks like a high-resolution satellite picture. A custom processing model is then used to generate a point representing the highest peak on each tree.

“Using statistical GIS (Geographic Information Systems), we can filter out non-trees and then subtract the ground measurement from the highest point of each tree to obtain the height,” Goodwin said. “We can inventory trees with 95% to 97% accuracy and extract measurements accurate to within 4 to 6 inches.”

To image the health of the trees, Goodwin and his team use a special camera on the drone that measures how much light the trees reflect in different wavelengths from infrared to blue light.

Applying vegetative indices to these images, such as NDVI (Normalized Difference Vegetation Index) and others, tree health can be displayed according to an easily interpretable color ramp,” he said. “Typically, dark green represents healthy trees and orange or red represents trees that are less healthy.”

From Christmas trees that are the perfect shade and height to chestnuts that produce the sweetest treat after roasting on the open fire, MSU research means that even during a unique year like this one, there are still some holiday traditions that will remain.