(2) "empty" means "white" and it's useless to send it. It's already May, and my wife at home sent me spring clothes, but it's useless at all, because the border "has not been flowered in May", which means that it's still very cold and the poet is still wearing a cotton-padded jacket. It shows that the people in the family are not clear about the poet's living conditions, expressing the poet's yearning for his relatives in his hometown and the loneliness of being single and unknown.