White oak trees are used to make Kentucky bourbon. Now there's a fight to preserve them

White oaks are quite the sought-after tree.

They provide food for some species, their bark makes nice nests for bats and they are used for bourbon barrels that help give color and flavor to the spirit Kentucky is best known for.

And now, data show the trees’ population could begin rapidly declining in 10 to 15 years without intervention.

“The big part of the regeneration problem in the forest is a lot of maple and beech are crowding out white oak,” said Barbara Hurt, the executive director of DendriFund, an environmental nonprofit. “So they don't get the shade, they don't get growth and they even die as young seedlings."

Since 2017, Kentucky distillery Old Forester and DendriFund, which was founded after a donation from the Louisville-based Brown-Forman Corp., have teamed up with other distilleries, universities, federal and state governments and even furniture makers for a program in which the trees are grown and preserved at nurseries across the state.

The program, dubbed the White Oak Initiative, includes a nursery at Brown-Forman's Old Forester distillery in Shively that is said to be the first urban nursery for the trees and helps provide insight on which environments the trees can adapt to.

"This is a super unique site because we can have a level of engagement," said Hurt, a fifth-generation member of the Brown family. "Oftentimes when you learn about forestry or seed research, you have to go deep into the woods ... so this actually brings this conversation and experience to a city setting, in an area that is easy to visit."

What makes a good white oak acorn?

The acorns aren’t just thrown into the ground to grow. It's a process. 

To start, acorns are collected from all over the region, including Alabama, Georgia, Tennessee, Kentucky, Arkansas, Missouri, Texas, Virginia, the Carolinas, Wisconsin and Maryland.

Last year volunteers collected over 100,000 acorns, including at the Jefferson Memorial Forest, Olmsted Park Conservancy and Bernheim Forest in Kentucky.

The acorns are then sent to Morgan County, where the Kentucky Division of Forestry has loaned land to the program for a nursery. There, the seeds are examined by University of Kentucky researcher Laura DeWald.

"Generally a tree is gonna produce good acorns," she said. 

But there are exceptions. Have bugs been eating away at the acorns? Are some too young? How is the weather?

White oak acorns germinate and begin forming root systems immediately after hitting the ground, unlike other species that wait until the spring. If an acorn floats in a container of water, that means weevil insects have likely hollowed it out by eating it from the inside. If the cap is still on or it is green, the acorn is too young and likely won't form a seedling. 

"You can pick a peach if it's hard and it will continue to ripen off the tree," said DeWald, who joined the program in 2019. "So a lot of tree species do that, but the species in the white oak ... (acorns) have to stay on the tree to mature. If birds or squirrels throw them off, those acorns that land on the ground will not mature."

The acorns stay at the research facility for a year. This year's batch of acorns will be planted in April 2022.

Going from an acorn to a tree

After a year, the seedlings, which are usually about 12 inches at that time, are uprooted and transported to distilleries, where they will remain until they mature, which takes about 50 to 60 years. 

At the nursery in Shively, 2921 Dixie Highway, researchers examine whether a tree goes dormant or begins growing leaves, or "flushing," on time. Flushing too early could leave the tree vulnerable to late spring frost, while flushing too late could mean it's not getting the full advantages of growing season. 

An urban environment also presents challenges. 

"Some of the things that make it more difficult is there's a lot of non-native and invasive species, both tree and non-tree species," DeWald said. "You generally have relatively compacted soils. The beneficial fungi that would normally be in the forest and associate itself with tree roots will not be there."

That fungi, mycorrhizae, has a symbiotic relationship with the trees, with the fungi providing water and minerals in exchange for sugars the trees create from photosynthesis. The fungi also help plants communicate with each other by sending nutrients across root networks. 

At the Shively nursery, a mycorrhiza fungicide is added to the soil. 

"When we add it back, it creates connections from tree to tree in the root, so that they're connected to one another," Hurt said. "So that's my favorite part about the establishment conditions that we're doing." 

What happens to the trees once they're established?

Because all the trees are being grown in a common environment, any differences can likely be attributed to a tree's lineage. 

"We call those progeny tests," DeWald said. "And so if the (offspring) ends up being superior, we go back to that original tree — that's the mother tree — and we collect material and we graft it. And then we use this grafted material to create seed orchards." 

A seed orchard has a mixture of young trees bred from the superior adult trees. These will eventually be expected to produce arable acorns after about 15 years.

At that 15-year mark, about 50% to 60% of the trees will be weeded out and discarded if they don't end up being as high quality as initially thought. 

Qualities that will be examined in a tree include how straight it grows, the number of branches it has and how insect-resistant it is. 

Hurt said the members of the initiative are still configuring a plan for the scrapped trees. 

"My intent is not for them to go to waste," she said. "My hope is that people would somehow get them. We'd be able to share the trees that aren't going to stick around for perpetuity." 

Contact Ayana Archie at aarchie@courier-journal.com or follow on Twitter @AyanaArchie. Support strong local journalism by subscribing to The Courier Journal.