The metaphor of England as a garden, and of Richard as a bad gardener, has come up before--most notably in Act II, scene i, in John of Gaunt's speech. Indeed, some of the same figures and images are used: for instance, the king's advisors Bushy and Greene are called "caterpillars" here (47), the same word Bolingbroke uses to refer to them in Act III, scene iii.
Moreover, we see once again the metaphors which associate the king with the land: the description of Richard defeat as "the fall of leaf" (49) reminds us not only of John of Gaunt's rich garden analogies in Act II, scene i, but also of the metaphor the Duchess of Gloucester used to refer to the death of her husband Thomas of Gloucester: "One flourishing branch of [Edward III's] most royal root... / Is hack'd down, and his summer leaves all faded / By envy's hand, and murder's bloody axe" (I.ii.18-21). The verbal echo seems to be loaded with ominous foreboding: if Gloucester died violently and mysteriously, what does it mean that Richard's leaves now are falling too? Already the king's assassination in Act V, scene v--the groundwork for which has been laid nearly from the play's beginning--is starting to look inevitable.