Like ranch dressing and Netflix, plants hold a special place in millennials’ hearts.

They ranked as the most desired hotel room amenity — plants, not condiments or streaming services — for 63 percent of vacationers, according to a recent Orbitz survey of U.S. travelers between the ages of 25 and 44. Nearly a quarter of the respondents said they’d shell out $50 to $100 more for plant-filled accommodations.

So the online travel site decided to give its millennial clients and plant-lovers of any age what they want: the chance to spend the night surrounded by ferns, palms and succulents at what’s being billed as the first plant pop-up hotel in Chicago.

The plan calls for transforming 10 guest rooms in the Kimpton Gray into leafy lodging for overnight stays at the boutique property Oct. 18 and 19.

The rooms, bookable exclusively at orbitz.com/plantpopup, are inspired by the city’s Garfield Park Conservatory.

The Fern Room, available as a king spa or king deluxe, will be stocked with lush greenery reminiscent of Chicago’s prehistoric landscape. Guests wanting more of a desert vibe can bed down in a king or queen deluxe decked out with cacti and succulents. Vanilla orchids and fruit-bearing plants will lend a sweet scent to the Sugar from the Sun room.

“It’s kind of like a mini-conservatory in the hotel,” said Carey Malloy, director of brand marketing at Chicago-based Orbitz.

Starting at $368 a night, the rooms come with green-themed amenities, like aloe face masks and green juice. Even the Kimpton tradition of an evening social hour is in on the act. All Kimpton Gray guests can partake in free cocktails with fresh herbs from 5 to 6 p.m.

“We’ve done a lot of pop-ups in our living room or various event spaces but never in our guest rooms,” said Dina Fenili, director of sales and marketing at The Gray. “It’s a fresh idea and we love it.”

Plant room patrons also get tickets to Fleurotica, the conservatory’s Oct. 18 fashion event, featuring runway looks made out of plants and flowers.

“Plants are the No. 1 thing millennials want in their rooms and I agree with them 100 percent,” said Garfield Park Conservatory Alliance president and CEO Jennifer Van Valkenburg, a Gen Xer. “We’re all crazy plant people here.”

lrackl@chicagotribune.com