(CNN) — Two bonsai trees worth thousands of dollars that require special care were stolen from a Washington state museum, the museum said.

Two people wearing hooded sweatshirts were seen slinking into a secure exhibit in surveillance video captured early on Sunday. The trees were on display at the Pacific Bonsai Museum in Federal Way, Washington.

“It’s a really defeating feeling because as the curator, ultimately, I am responsible for their physical care,” museum curator Aarin Packard told CNN on Tuesday. “It’s very frustrating and really discouraging when you’ve invested years and not just my time, but all of the people who have tended to these plants cumulatively for 75 years.”

Museum officials hope the trees are returned, as they likely won’t be able to survive without someone’s expert care.

“There are a lot of misperception about bonsai,” museum executive director Kathy McCabe told CNN. “Unless it’s a tropical plant or tree, they’re meant to be outside. They can have a turn in their health pretty quickly.”

When temperatures dip below freezing, museum staff put covers on the trees and individual heaters on them, she said. Watering is the biggest need for the miniature trees year-round.

A Japanese Black Pine was one of the trees stolen.

A Japanese Black Pine was one of the trees stolen.

From Pacific Bonsai Museum

One of the stolen trees is a Japanese Black Pine that was grown in a tin can during World War II, the museum said. Juzaburo Furuzawa tended to the plant while he was incarcerated in a Japanese internment camp more than 70 years ago.

The other plant is a Silverberry, which began training as a bonsai in 1946. It was created by a female bonsai artist named Kiyoko Hatanaka, a pioneer of her time.

A Silverberry that began bonsai training in 1946 was also stolen.

A Silverberry that began bonsai training in 1946 was also stolen.

From Pacific Bonsai Museum

While the museum cares for about 150 trees, there are only 50 or 60 of them on display at a time, McCabe said. The museum wouldn’t give an exact value of the two trees, but she said it was in the thousands.

This isn’t the first time someone has stolen a bonsai from the museum, she said. In 2015, a thief ran off with a juniper bonsai.

The tree was returned within a couple days, but it was severely damaged.

“It had been pruned and taken out of its pot. It was taken to the bonsai ICU,” McCabe said. “It’s been off display for years, but it is recovering.”

McCabe hopes that going public with what happened will help the museum gets its prized trees back. If someone brings them back, no questions will be asked.

“We thought there would be a chance of recovering these trees,” she said. “They’re irreplaceable, they belong to our community and they have deep stories to tell that only these trees can do.”