The love notes - there are 11 - are the brainchild of Philadelphia advertising agency Masterminds, which took TreePhilly on as a pro bono client about a year ago and came up with the "City of Arborly Love" campaign. The "come hither" vibe was intentional.
"People from Philly are really passionate about things. So we wanted to find something else people love, like trees," said Jennifer Fink, a Masterminds vice president.
The messages - saucy declarations such as, "I'm nuts about you," or, "I like big trunks," or, "You can nest in me any day" - include the hashtag #TreePhilly, and Smith said there had been good feedback on social media.
Nevertheless, some passersby this week hardly noticed the signs or were confused about the messages.
Kevin Gaskins, 36, a hair stylist, had not noticed them even though his walk to work takes him along Chestnut and 16th Streets every day.
"It's a good concept, but I wouldn't have understood it," he said.
The love notes piqued the interest of clerk-typist Kizzy Richard, 36, who wished the signs pointed to a website, instead of a hashtag, that told people how to get more involved.
"I think it's great," said Barbra Chigounis, 34, an art teacher. "If I could, I would pick a maple in a minute."
She is renting in Philadelphia, so she can't receive a free tree.
Since 2012, TreePhilly has held two tree giveaways a year, in fall and spring. This is the first time it has tried a new kind of outreach to promote the giveaway. The messages, which went up Feb. 10, will be taken down at the end of the month.
To sign up for a tree, go to treephilly.org. The deadline is March 27. The trees, 11 native species, including red maple and Moorpark apricot, will be handed out in April.