As his plants grew, Zaslow started borrowing space from farmers, placing the trees outside his own backyard. He says it is a “massively expensive” endeavor to make this work in an area like Baltimore, where temperatures hit below freezing.

“Citron trees are very tender trees. Thirty, 28 degrees and the fruit will die and the tree will die after that,” he says, explaining that farmers use propane to keep their greenhouses an optimal temperature to keep produce alive through the winter. “It could easily be hundreds and hundreds of dollars a month if I were to try to do this alone. The beauty of it is that there have been many bitter, cold winter snowstorm nights where it has been 10 degrees outside with wind at 30 miles an hour, and the only thing separating the weather and the trees from that air is a little bit of plastic, 6 millimeters thick. And they survive. Wow!”

Zaslow threw himself into the project, including becoming a self-proclaimed botany expert by reading every book in the local library and through extensive Google searches. He also helps educate young yeshiva students and community members about the halachot (Jewish laws) of planting through the trees.

For example, “We talk about an etrog that grew without a pitom (the little brown stick tip at the top of the etrog fruit). When you study etrog trees you see that there is never an etrog that grew without a pitom. Every etrog begins life with a beautiful yellow pitom out of the middle of the flower. But about a month later, a little green etrog comes out underneath. At that point, sometimes the pitom falls off. Then the fruit will grow six months without the pitom.”

Zaslow is also able to discuss the laws of orla, the Torah commandment to wait for three years before partaking of any fruit from fruit-bearing trees. He says many people think the fruit is going to waste, but that most fruit trees don’t bear any fruit for the first three years.

“How big can an etrog be in order to be kosher? How small?” Zaslow asks.

According to law, he explains, an etrog needs to be larger than an egg. A kosher etrog must be able to be held in two hands—about the size of a watermelon. Moreover, he says, etrog trees are unique in that they can have generations of etrogim on the same tree. New fruits can sprout as older fruits are not yet picked.

Rabbi Moshe Hauer, head rabbi of Bnai Jacob Shaarei Zion in Upper Park Heights, calls Zaslow’s project “beautiful.” He tells JNS.org that Zaslow has brought an extra dimension of appreciation for, and a personal connection to, this special mitzvah.

“By exposing us city dwellers to the delicacy and beauty of the growth of the etrog, Darrell has deepened the experience of using the etrog and enhanced our appreciation of God’s creation,” says Hauer.

Zaslow has traveled with the trees across the Mid-Atlantic region and to New York to share his plants.

What’s next?

“Someone has to be able to grow etrogim on the Moon,” Zaslow quips. “If humankind is going to set up colonies on the Moon, there will be yidden (Jews) there. We need to know how to do that. If you can do it in Baltimore….”

But Zaslow is not interested in doing it himself. He says he is looking for a successor to take over the project.

“Anyone can do it,” says Zaslow. “The most important thing is you have to daven (pray) that Hashem should bless the trees and the fruit and make them a thing of beauty.”