The space between is but an hour, the frail duration of a flower."
The poem is about life. The first stanza describes a babe in the womb. Untouched, unseen, and protected. The second talks about childhood, being protected in shade and from vulgarity. The third is about aging to the prime of life "nor were those flowers more gay, The flowers that did in Eden bloom." Freneau includes foreshadowing of the impending decay.
The flower dies in the fourth stanza and leaves no trace. It's almost as if it was never there. Although the honeysuckle has gone through these changes, it's life was short.
Basically, Freneau tells us that our lives are also frail and short and are all equal in death.