Yellowbud hickory, the olive oil of the North?

Driving on Tucker Hill Road, one might notice groups of white plastic tubes sticking up in an open area behind a stone wall. This is the work of Miller Ward, and it’s one of a number of projects that are fueled by his avid interest in regenerative agriculture, permaculture, and the environment. It so happens that this field at his parents’ home on Tucker Hill Road offers a perfect site on which to grow a stand of nut trees – yellowbud hickory to be exact – that offer the promise of a more sustainable approach to agriculture. The plastic tubes shield the young trees from browsing deer. Miller calls these and other trees “powerful allies” in restoring the land while keeping it productive.

Yellowbud hickory (Carya cordiformis) goes by the more common name of bitternut hickory, which explains why this useful tree has been largely spurned by farmers and orchardists of European descent. Its nuts are described as intensely bitter and astringent. Indigenous peoples, however, extracted an oil from nuts of several different hickory species, including yellowbud, by boiling the crushed nuts in water and skimming off the floating oil. They also made a drink called “pokahichary” from hickory nuts pounded with water, from which the word “hickory” is derived.

Compared to chestnuts and walnuts, yellowbud hickory remained obscure until recently. Now there is a surge of interest in the species. 

It turns out that the kernel of the nut has a high oil content – 75 to 80% – that is high in oleic acid, a compound touted for health benefits like lowering cholesterol and reducing inflammation. The trees yield abundantly, and a cottage industry, encouraged locally by the White River Natural Resources Conservation District, has sprung up around gathering and processing the thin-shelled nuts for oil. Miller has friends in Western Massachusetts who have a “proof of process” yellowbud nut oil pressing operation. And the bitterness? That is caused by tannins which are water-soluble, not oil-soluble. They stay behind in the “press cake,” the solid residue that remains after the oil has been squeezed out of the crushed nuts. Yellowbud hickory oil has a mild, pleasantly nutty flavor. Its utility in the kitchen could match that of olive oil, which it rivals also in oleic acid content.

Miller points out that there is a lot of potential for improving the species for even larger crops. The trees of today are completely wild; yet preliminary research indicates that, on average, they can yield the same amount of oil per acre – 41 gallons – as sunflowers in the northeast. Only recently has there been any attempt at selecting individuals with high productivity. A midwest organization called Yellowbud Farm specializes in tree crops and reports on a selection of yellowbud that produced about five times more nuts than average. When yellowbuds are cultivated in an open sunny location rather than a shady forest, they can begin bearing at six years of age, rather than the 30 years reported by the US Department of Agriculture. And it is likely that irrigation would increase yields even more, since pecans, a hickory relative, produce twelve times more nuts when irrigated. 

Obtaining vegetable oil from trees has other benefits. Major oilseeds like canola are annual crops requiring herbicide application to reduce weed competition. These annuals are grown in monocultures covering vast acreages (2.3 million acres of canola in the US alone), and periodically these areas need to be tilled, inviting erosion and windblown loss of topsoil. By contrast, trees soon grow taller than the “weeds” of the understory and allow for a multi-layered use of the land. In a system known as silvopasture, grazing livestock are integrated with trees. The animals fertilize the soil and keep ground vegetation trimmed to facilitate the gathering of nuts. Trees shade the animals from summer heat and provide them some amount of protection from wind and rain. While rotational grazing is necessary to limit browse damage to the trees, there is little need for tilling and herbicide spraying, and the farmer enjoys a more diverse range of products.  Silvopastures can increase the populations of wildlife like turkeys and quail, while songbirds benefit more from silvopastures than open grazing land. The forage plants in the understory also protect soils from erosion, while the deep roots of trees and their associated fungi (mycorrhiza) mine minerals from the deep soil and bring them to the surface. Trees, unlike monocultures of annuals, sequester and store large amounts of carbon for the long term, a crucial function in the face of climate change.

It would seem that yellowbud hickory lends itself well to the silvopasture system. The trees cast an open shade that allows forage plants to grow beneath them. They tolerate a variety of soils and are deeply tap-rooted, so they don’t blow over in windstorms. In addition, their adaptable nature allows them to grow anywhere in the eastern US, from northwest Florida up into southern Quebec, suggesting they will be survivors under climate change. A study from Cornell University found that the foliage of yellowbud hickory has a high calcium content, and it is near the top of the list of soil-improving species. These attributes lend themselves well to regenerative agriculture that seeks to restore the health of soils and ecosystems.

Miller’s interests in agroforestry don’t stop at yellowbuds. The oak is another under-utilized nut-bearing tree, though oaks are notorious for producing a huge crop some years (mast years) and paltry crops at other times. The tannin in acorns makes them unpalatable to humans without lengthy processing; however, pigs don’t seem to mind it. Why, Miller ponders, don’t people grow oaks and collect the acorns to give to local hog farmers in return for a reduced price on a cut of pork? And it need not stop at acorns. Honey locusts, native persimmons, pawpaws, and hybrid chestnuts could all be cultivated in peoples’ yards to provide livestock or human food in the form of their fruits, instead of non-native invasive trees like Norway maple, Amur maple, and Tree-of-Heaven. 

Miller is not yet a permanent fixture in Thetford. He’s looking at graduate programs, though it is hard to choose among his wide range of interests that span regenerative agriculture, permaculture, watershed restoration, beavers, and more. That’s why he started his hickory plantation of about ten trees now (with 40 more distributed to the community). He knows they will be getting a head start for when he returns and will someday be slender trees 50 to 70 ft  tall, with pyramid-shaped crowns. They come from a selected stock that he might choose to multiply through grafting or just leave to produce their mild, nutty flavored, and healthy oil.