Lovelorn – Sad because the person you love does not love you
The love the gardener felt for his lawn (lovelorn) made him feel sad because the lawn could not love him in return.
Examples of lovelorn in a sentence
The lovelorn teen sat staring but she ignored him.
I had felt lovelorn for far too long, so decided to ring them.
She turned up at his door every day for a week, acting like a lovelorn teenager.