Where It All Goes Down
Gardens are important in "The Garden" for lots of reasons, but in this section we're going to use our super-Shmoop vision goggles and focus in on the kind of garden Marvell is trying to create in his poem, namely a hortus conclusus. For those of you who aren't Latin scholars, hortus conclusus is a term that literally means "enclosed garden." In the world of landscaping this simply means a garden that is somehow cut off from the natural world by a wall or barrier. In the world of art, poetry, and literature, it's a little bit more important than that.
The person most frequently associated with the hortus conclusus is the Virgin Mary because, in accordance with Christian theology, her womb needed no "planting" in order to become fertile, therefore leaving her "garden" closed off from the Josephs of the outside world. Moving into the abstract, the hortus conclusus can also represent safety, fertility, privacy, secrecy, sacredness, innocence, or basically anything else associated with keeping bad things out and good things safe from contamination and danger.
It seems, then, that the speaker imagines an enclosed garden so that the evils, stresses, and people of society can be kept out of his "happy garden-state" (57), leaving his soul free to fly around like a bird, chill in the trees, and basically do whatever it wants. Line 58 even goes as far as claiming that paradise was more paradisiacal "while man there walked without a mate," indicating that the speaker is in serious need of some alone time.
But Marvell's garden isn't actually enclosed. The speaker talks of a "Paradise alone" in a wistful, longing way; if he were already alone in Paradise, we imagine his tone would be more like "I'm hanging here by myself and it is awesome!" The poem spells it out for us, too; we learn in the same stanza that " [it] 'twas beyond a mortal's share / To wander solitary there" (l61-62). And if Adam wasn't allowed to live alone in Eden before the Fall of Man, our speaker basically doesn't have a chance of getting what he wants. So is the speaker merely dreaming of an opportunity he knows he will never have? Or looking forward to a "Paradise alone" that he hopes will come in the future? Is it even worth dreaming about something that you know will never come true?
Finally, your interpretation of exactly what is invading the garden depends on your reading of the poem. If you take it in a political sense, you might think the garden is being invaded by the social corruption the speaker rails against at the beginning of the poem. If you see this as a commentary on romance and sexual relationships similar to what we see in stanza 4, you might think of the garden as being invaded by some seductress that is distracting the speaker from his thoughts. Scholars have argued these views and everything in between, but Shmoop is looking into claims that garden gnomes are ultimately to blame.