The ability to describe something convincingly will serve a writer well in any kind of essay situation. The most important thing to remember is that your job as writer is to show, not tell. If you say that the tree is beautiful, your readers are put on the defensive: "Wait a minute," they think. "We'll be the judge of that! Show us a beautiful tree and we'll believe." Do not rely, then, on adjectives that attempt to characterize a thing's attributes. Lovely, exciting, interesting – these are all useful adjectives in casual speech or when we're pointing to something that is lovely, etc., but in careful writing they don't do much for us; in fact, they sound hollow.