| Quote #1
in your most frail gesture are things which enclose me, (3)
The speaker's lover has tons of power over him, but it's not because she smacks him around or anything. Instead, it's her frailty that attracts him so much. Her control over him isn't physical at all.
| Quote #2
your slightest look easily will unclose me (5)
Here again we see that it's the lover's subtleness that gives her the power to open the speaker up at will. She doesn't have to glare at him. All she has to do is give him a glance.
| Quote #3
you open always petal by petal myself as Spring opens
Now the lover is really starting to sound mega-powerful. By comparing her to Spring, the speaker makes her seem like an irresitable force of nature. Once again, though, her power is subtle. It's not like Spring goes around slapping flowers until they bloom, right? Instead, they're gently coaxed into blossoming by rain, sun, and warm weather.