The ‘crow’ and ‘hemlock’ represent something negative. They are usually taken as symbols of sorrow.
The poet uses the crow and hemlock tree to convey the idea that we can find joy even in dark things.
Final Answer: The crow and the hemlock tree both represent grief. The dust of snow shaken off the hemlock tree by the crow stands for happiness that Frost experiences on a gloomy day. Hence he has used an unconventional tree and bird to compare them with joy.
