At the beginning of the poem "Virtue," the speaker reflects upon and mourns for the ephemeral nature of beauty. In the opening stanza, for example, the speaker says that when the beauty of a new day should fade at dusk, the dew itself "shall weep" for the "fall" of the day. In the second stanza, the speaker makes much the same point when he describes as "rash" the "gazer" who is moved to tears by the beauty of a rose. The implication is that the "gazer" is "rash" because he has allowed himself to be moved too much by a beauty which cannot last. The rose seems to have sympathy for the "gazer" when it asks the "gazer" to wipe the tears from his eyes.
Immediately after the rose asks the "gazer" to "wipe his eyes," the speaker says of the rose, "Thy root is ever in its grave." The idea conveyed by this rather abstract image is that the death ("grave") of something beautiful is always contained within its birth ("root"). In other words, nothing beautiful can last forever.
Although it is certainly sad and depressing to consider that beauty can never endure indefinitely, it is also true that the beauty of something is intensified precisely because it is short-lived. In other words, if the rose were to live forever, then perhaps its beauty wouldn't be as special, and therefore the rose would not be as beautiful. The beauty of a rose is so special because it is temporary, and thus unique. If the "gazer" had understood this, then perhaps there would have been no need for the rose to ask him to "wipe his eyes."