Nature can do no more — Menses

Nature can do no more 1
She has fulfilled her Dyes
Whatever Flower fail to come
Of other Summer days
Her crescent reimburse 5
If other Summers be
Nature's imposing negative
Nulls opportunity-
(F.1722/J.1673)
[1] Nature:: the nature of a woman's body.
[2] She has fulfilled:: a woman has accomplished, completed. her Dyes:: colorful things in her life (children), and from her body (menses); she has completed the mission of a woman's nature of periods.
[3] Flower:: the menstrual discharge (OED flower n. 2b, 1527, 1859). Flower fail to come:: her period failed to come, a hint on pregnancy.
[4] Summer days:: passionate days.
[5] crescent reimburse:: the slow increasing to compensate her menses discharge.
[6] other Summers be:: there will be other passionate days.
[7] Nature:: menses.
[8] opportunity:: the chance to get pregnant.