Every season is hemp season! This winter, Northwest Crops & Soils Program (NWCS) is exploring winter retting as an option for Vermont farms looking to grow textile-grade hemp. Retting is a necessary process that bast fiber crops must undergo to release and separate the natural fibers found in the stalk. Typically, this process commences in late summer once the crop has been cut. The two main types of retting are field retting and water retting. In field retting, plants are laid on the ground to be colonized by microbes, who then eat the pectin and lignin that bind the fibers into tightly glued bundles. In water retting, the freshly cut stalks are submerged in a tank of water to produce a similar outcome.
NWCS is conducting trials with a third type of retting called winter retting. This method is largely a mechanical process, while field and water retting rely on microbes to break down the stalk. The process of winter retting involves leaving the plants standing dead through the winter months to weather and degrade through exposure. The freeze-thaw cycle softens and loosens the fibers from their natural glues.
The Northeast might be the perfect host for the winter retting technique for one reason alone: we have a winter. Winter retting is touted as having many advantages over the two other retting techniques described. For one, harvesting dead plants is a lot easier than harvesting vigorous hemp plants in their prime, with strong green fibers ideal for wrapping around fast-moving, high-powered equipment. There are also no adverse environmental outcomes to winter retting, while water retting creates hazardous wastewater that must be treated and disposed of properly. NWCS Team members Laura Sullivan and Shannon MacDonald are pictured here harvesting winter retted hemp for analysis.
The winter-retted hemp is being harvested in one-month intervals to observe the fiber over time. Samples will be evaluated using a variety of methods in hopes of creating a comprehensive picture of the winter retting process. Some samples will be sent to Cornell’s Dairy One Forage Lab to undergo a wet chemistry analysis that will look at the degradation of pectin, lignin, and hemicellulose. Other tests will evaluate samples for characteristics like tensile strength. Aside from the data collection, the bulk of the fiber will be processed on our research farm in Alburgh, Vermont, and then sent to Battenkill Fibers in Greenwich, New York for spinning.
Last spring, we sent Battenkill a preliminary batch of hemp fiber from our 2023 season to be blended with local wool, thus creating the first commercially spun, all-local, hemp-wool yarn in the region, or maybe even the country. See picture above.
The overall goal of this project is to learn how to grow and process fiber in the northeast that meets the specifications of established processors like Battenkill to close the loop of regional production and empower farmers to do the same. Our prototype yarn has given us proof of concept that this work is feasible. We’re excited to see the results of subsequent runs alongside the quantitative data, which should be finalized in July 2025. This work has been made possible with funding from the USDA Sungrant cycle and can be identified as award number AWD00001779.