An unweeded garden takes all the joy away from a garden that should be beautiful. Hamlet is still in mourning for his father's death, and what disturbs him most is that his mother has married his father's brother, as if she is not in mourning for his father any longer. In Act One, Scene Two, Hamlet's world is an unweeded garden at this moment:
It is an unweeded garden
That is going to seed, only things that are decaying and
Disgusting grow there. That it should come to this!
Only dead for two months!
Clearly, Hamlet cannot accept his mother marrying his Uncle Claudius. His heart is ripped in two. His world is full of decay and disgust as is a garden that is unweeded. There is no beauty in his world at the present. Not only has he lost his father, but he feels he has lost his mother. He feels that she should have mourned longer than two months. Well, actually, Hamlet is upset because it has been less than two months:
Only dead for two months! No, not so much, not two.
So excellent a king that, compared to this king, was
A magnificent man to a beast, so loving to my mother,
That he might not allow the winds of heaven
To blow on her face too roughly.
Hamlet compares his world to a decaying, unweeded garden. He cannot find beauty in his world because his father is dead and his mother is already married to his Uncle Claudius.
This is one of Shakespeare's most brilliant metaphors. Shakespeare is expressing his own view of humanity through one of his characters. Hamlet is saying that most of the people in the world are either rank or gross. There is a big difference in those two words. An unweeded garden that grows to seed can be an interesting object of study. In fact, it is a wonder that artists such as Monet and Van Gogh did not paint unweeded gardens. The things that are "rank" in such gardens are the kinds of plants that do not grow tall but choke the flower beds and encroach on the walks, helping to create a picture of abandonment, failure and desolation. Lawns that are not mowed will either become dead and brown or else, if they can get enough rain water, will become thick and ragged-looking. The tangled individual plants will appear to be fighting for a foothold on the soil and a place in the sun. This is how Shakespeare perceived the majority of humanity--fighting one another to stay alive and not being worth the effort. He expresses a poor opinion of people in many of his plays, including King Lear, Macbeth, Measure for Measure, and Timon of Athens. Perhaps he thought of people as being weeds and neglected plants in a garden because such plants give the impression of fighting for their lives--every man, and every weed, for himself.
In addition to the vegetation that is rank, there are some weeds that take advantage of the untended condition of the garden to grow to their full height and even develop ugly flowers. Such tall weeds are usually marvelously ugly and misshapen. Milkweeds are a good example of weeds that are "gross." And Shakespeare's Hamlet is thinking that many humans who stand out above the masses are remarkably ugly, or "gross." The best example of a gross human being in Hamlet is King Claudius. He is a villain, a liar, a drunkard, and a lecher, but he is a very interesting character. He stands out above the common herd of men who are "rank." Claudius is one of the outstanding individuals who can be described as "gross." Shakespeare's metaphors and similes are almost always simple, natural, unpretentious, and strikingly appropriate.