1 The Garden of Proserpine this hight;

hight > was called; is called

2 And in the midst thereof a silver seat,

a > [was a]

3 With a thick arbour goodly over dight,

goodly > gracefully over dight > [trained to overhang; "dight" = "prepared">[

4 In which she often used from open heat 5 Herself to shroud, and pleasures to entreat.

shroud > shelter entreat > occupy herself in (this instance cited by OED)

6 Next thereto did grow a goodly tree,

goodly > beautiful