Walking through Central Park about three years ago, the Spanish artist Manolo Valdés saw a man sunbathing, with monarch butterflies swirling around his head.


That image — along with an exhibition of tropical butterflies at the American Museum of Natural History and a Spanish expression describing people with a lot of ideas as having butterflies in their heads — kindled something in the artist.


“All of a sudden, they were everywhere,” Mr. Valdés said of the butterflies in an interview at his Manhattan studio. “That’s how ideas start. You never know when one is going to pop in.”


The result is a 50-foot-wide sculpture of a woman’s head surrounded by butterflies, one of seven immense bronze, steel and aluminum works by Mr. Valdés that will be placed throughout the New York Botanical Garden in the Bronx for “Manolo Valdés: Monumental Sculpture,” an exhibition that opens on Sept. 22.


Some of the sculptures are as much as 17 feet high, and some weigh as much as 20 tons.


“We’re always looking for big work that will enable us to bring new people to the garden but also inspire people to look at the garden in new ways,” said Gregory Long, the garden’s president and chief executive. “The trees are 120 feet tall. Small works of art don’t make any impact.”


Mr. Valdés designed the sculptures in his Manhattan studio, but they were made in a Madrid foundry and shipped to Baltimore, then transported by truck to New York. “We needed 21 trucks to send the show,” said Pierre Levai, the president of the Marlborough Gallery, which represents Mr. Valdés and is sponsoring the exhibition.


Mr. Valdés said he was pleased that the duration of the show — it runs through May 26 — will allow the public to see his sculptures through different seasons: when the surrounding trees are red with changing leaves, white with snow, stark in their bareness and green with buds.


“When you see a sculpture in the street, the way you look at it is dependent on the surroundings, the light, the time of year,” said Mr. Valdés, 70. He wore paint-splattered coveralls and khaki Crocs and spoke in Spanish while his daughter, Regina Valdés Montalva, interpreted.


The garden became aware of Mr. Valdés through his street sculptures, specifically the 16 that were erected in 2010 along the Broadway Malls, the landscaped medians running from Columbus Circle to 168th Street. Those bronze sculptures, in the same semi-figurative style as those that will occupy the garden, were inspired by old and Modern masters like Zurbarán and Velázquez, Matisse and Lichtenstein.


The garden, of course, is a very different environment for displaying Mr. Valdés’s works; for one thing, installing them on grass-covered earth will mean considerable repair work to the ground, once they are gone. In addition, Mr. Valdés noted, people will stroll among them on a walking tour organized by the garden, not hurry by on their way to buy coffee or get to the office.


“It’s different when you go to the garden with a purpose of lounging and looking at things,” he said.


All of the sculptures in the new exhibition feature a female head in some kind of headdress. In designing the works — three were created expressly for the exhibition; the others were adapted from earlier versions — Mr. Valdés said he drew on the garden’s horticulture, namely the bombax trees and ferns which, because of their semi-transparency, reminded him of the latticework of the Alhambra in Granada, Spain.


For “Ivy,” the headdress is made of swirling rods that evoke open fans and palm fronds. The headdress in “Guiomar” depicts foliage that Mr. Valdés modeled after fern specimens he saw in photographs of the garden. “Fiore” has a floral theme that evokes Matisse’s still-lifes.


Mr. Valdés said he chose not to use bronze in the sculptures themselves because of the risk that the metal would begin to blend with the surroundings, turning green as it was exposed to the elements and preventing the sculptures from standing out.


Instead he used bronze only in the pedestals, choosing aluminum for much of the sculptural work because of its shine and reflective qualities. He also used Cor-Ten steel, which provides a rust-colored patina that he thought would complement the surrounding colors.


Although Mr. Valdés is from Valencia and has three studios in Madrid, he said he was stimulated by New York. (He lives on the Upper East Side and works near Union Square.) “When you’re in a place where it feels like you’re learning every day, you don’t want to work anywhere else,” he said.


Mr. Valdés’s work is featured in 40 public collections, including those of the Metropolitan Museum of Art; the Menil Collection in Houston; and the Centre Pompidou in Paris. He has permanent sculptures in many places, including Beijing, Madrid and Bilbao. But he said he didn’t mind that his work at the garden would be temporary and that he would see it dismantled come spring.


“It’s good that things change because you’re allowing somebody to see a lot of different art, and it’s not stagnant,” he said. “If you don’t like what you’re seeing, it’s not there forever.”