The last Friday in April is National Arbor Day in the United States . Arbor Day celebrates the role of trees in the world around us . Each year , organizers call on Americans to plant trees and care for them . In 1872 , a Nebraska man named J . Sterling Morton proposed the first Arbor Day . It became a legal holiday in the state 13 years later . Today many states observe Arbor Day on different dates throughout the year based on best planting times in their area . In North Dakota and Vermont , for example , Arbor Day is celebrated on the first Friday in May . A non-profit group called the Arbor Day Foundation operates the ArborDay.org website . It notes that “tree planting festivals are as old as civilization . The tree has appeared throughout history and literature as the symbol of life .” Trees do a lot for the environment . They clean the air around us . Some trees , such as apple and pear , give us fruit . Trees also provide shade for us and other creatures . Some animals build their homes inside trees or on strong tree branches . People and animals can use the wood from trees for building materials . You might find this strange , but trees can be fun to watch . You can just sit back and watch birds high up in the trees . And that brings us to our expression for today : to bark up the wrong tree . In fact , this expression is more like an idiom . Now , you might think that “bark ” in “to bark up the wrong tree ” means the strong , outer covering of a tree . But that is not the right “bark .” In our expression today , “bark ” means the sound a dog makes . Dogs bark a lot . They bark when they want to go outside for a walk . They bark with they see other dogs . They bark when they chase other animals , such as cats and squirrels . Now , imagine that a dog chases a squirrel up a tree . That is a lot of work – for the dog , that is . Dogs cannot climb trees . Squirrels , on the other hand , are expert climbers -- of trees and just about anything else . A squirrel may go up one tree but then jump to another . The dog simply can't follow the squirrel . So , it stays on the ground barking and barking up the wrong tree . And that is where we get our idiom . When a dog barks up a wrong tree , they are barking up a tree that no longer has their prey – the squirrel . For people , barking up the wrong tree means following a mistaken plan of action . If I bark up the wrong tree , I am doing something that will not get the result I want . I am wrong about the reason for something or possibly the way to get something . For example , at a party I notice that my co-worker Jonas is interested in a good friend of mine named Ursula . But Ursula is happily married , which is bad news for Jonas . So , I say to him , “Jonas , I know you want to ask Ursula out on a date . But you are barking up the wrong tree ! She is very happily married .” Now , let me tell you about another person who used the wrong way to get something . A friend of mine , Sharon , needed money for her new business idea . So , she went to an event to meet possible investors . However , the only people she met were other people looking for money . She spent the whole time barking up the wrong tree ! Now , keep this in mind when using this expression . While Americans do say “bark up the wrong tree ,” we would not say “bark up the right tree .” I would just say , “Welcome ! You've come to the right place !” Join us again next week when we explore words and expressions in American English .