The image shows a large outdoor sign, likely situated at the entrance to a nursery or garden center. The sign is a classic reader board style with movable letters, which allows for custom messages. The message spelled out on the sign says, "YOU CANT PLANT FLOWERS IF YOU HAVENT BOTANY."
Below the main image of the sign, there is a caption that reads "My local nursery went full dad joke." This caption gives context to the image, indicating that the photo was taken by someone who lives near this nursery, and it also highlights the nature of the humor involved—a "dad joke."
The joke on the sign is a play on words, combining knowledge about the subject matter of the nursery, which is plants and specifically flowers, with a pun. "Botany" is a field of biology that studies plants, and its use here is intended to sound like "bought any," which is phonetically similar in many English accents. So, the sign humorously implies that one must have purchased flowers (or perhaps studied plants) before they can plant them.
The humor in this image may be considered funny to people for several reasons. First, it's a pun, which is a common form of wordplay that often incites a mix of amusement and groans. Puns are a staple in "dad jokes," which are typically characterized by their innocent humor and playfulness with language.
Second, there's an element of surprise and cleverness in the way the phrase YOU CANT PLANT FLOWERS IF YOU HAVENT BOTANY