Sentence:  [T]he only reason that buckwheat is considered valuable as a <WSD>honey plant</WSD>, is because it blooms generally in dry weather late in the fall, when the difference in the temperature between two o'clock in the day and two o'clock at night is sufficient to favor the production of honey. 
Meaning of the word marked with <WSD> tags:  Any plant, all of them eudicots, from which bees usually collect nectar, pollen, or both for making honey.