Long article at Curbed about the history of Christmas trees:
[His] innovation was simple: He was the first to go over the heads of the middlemen and source trees himself and the first to discover the power of an obscure city ordinance called the Coniferous Tree Exception. Adopted in 1938 amid a dispute between Mayor Fiorello La Guardia and street peddlers, it says that anyone can sell trees on the sidewalk if they get permission from the nearest business.
I’ve met several people who’ve sold Christmas trees for [him]. Almost all of them asked to remain anonymous for fear of reprisals. They said that to work for [him], there is no interview and there is no application. The only way to enter his network is to be referred by an insider. You and a partner — [his] sellers always work in pairs — call a number around October, and a voice instructs you both to show up at a certain location (typically a sidewalk outside a bodega) around Thanksgiving. When you arrive, the two of you wait, possibly hours, potentially days, for another phone call from a different number. A new voice instructs you to construct a small shack out of pallets, plywood, even garbage, then continue waiting for the arrival of hundreds of Christmas trees, which will soon appear overnight along with clippers, chain saws, and plastic netting. You are instructed to sell each tree at the highest possible price.
It’s cash only. The money is collected each day by a person who pulls up in a black SUV unannounced.
[He] is said to occasionally appear to buy trees from himself. He doesn’t use a disguise because no one knows what he looks like.