Symbolism, Imagery, Allegory
The only healthy social space in the House of the Seven Gables seems to be outside, in the garden. That's where Clifford and Phoebe go so that Clifford can heal in the presence of fresh air and lovely flowers. And it's where Phoebe, Clifford, Hepzibah, Mr. Holgrave, and Uncle Venner get together on Sundays to enjoy one another's company. As the home of Mr. Holgrave's careful vegetable planting, the garden seems to be keeping back the "rank weeds (symbolic of the transmitted vices of society)" (6.2) that constantly threaten to return and overwhelm the Pyncheon family home.
The Pyncheon garden is a breath of fresh air in the middle of the heavy past represented by the house. It also represents the best of the Pyncheons. When Judge Pyncheon has died and all that's left are Hepzibah, Clifford, and Phoebe, Alice Pyncheon's flowers – Alice's Posies – are "flaunting in rich beauty and full bloom to-day, and seemed, as it were, a mystic expression that something within the house was consummated" (19.4). In other words, the full bloom of Alice's Posies in Chapter 19 represent the end of a process: with Judge Pyncheon's stroke, the family curse has died. Now Phoebe Pyncheon will have space to flourish happily like the flowers she loves so much.