One of nature’s oddities has occurred in a northwest Lawrence field where limbs from two trees have joined into one, creating something like a wooden set of Siamese twins.

Kansas University tree expert Valery Terwilliger said she had never seen it happen before.

“I’ve seen a lot of weird things in trees, and this is another one. But it’s still possible,” Terwilliger said.

Terwilliger, an associate professor of geography, studies trees’ responses to the environment. She compared the fused limbs to the horticultural process of tree grafting.

It is not known for certain how the trees came to attach themselves to one another.

“You never know what those guys are going to attach themselves to,” Terwilliger said.

John Ross looks at two trees that have merged branches. Ross was at the site in northwest Lawrence Thursday.

John Ross, of Lawrence, said he discovered the attached trees one day a few years ago while mowing the field near Spring Hill Drive and north of the Hy-Vee store at 4000 W. Sixth St.

“I just thought it was kind of a unique thing,” Ross said. “It’s something you’re not going to see every day.”

Terwilliger looked at a photograph of the trees on Friday. She was unable to identify the trees’ type without looking at their leaves, but she said they appeared to be either oak or hackberry.

Terwilliger also observed a bulging on one of the trees near a major joint that may be from insects or some other type of attack. The bulging is the equivalent of “tree cancer,” she said.

It may have caused the tree to reach out with a branch that eventually grafted itself to the limb of the nearby tree.

“They will exchange fluids. They will just form a connection. Otherwise, it might just die,” she said of the paired trees.

Terwilliger said it is more common for trees to conjoin near the bottom of their trunks.