How is time portrayed in "Loveliest of Trees, the Cherry Now"?

If you mean "by what means" is time portrayed, it is
portrayed by the image of the trees and their flowers.  If you are asking what time is
portrayed as, it is portrayed as something that is fleeting and quickly
gone.

Time, in this poem, seems to be measured by springs
and by the flowers that come out at this time of year.  The speaker talks about
"springs" many times in the poem.  So if you are asking what the speaker uses to mark
time, it is spring.

But what is time like?  Well, the main
thing going on here is that time is flying and will fly by quickly.  Time is something
that you have to hold onto as hard as you can because it will soon be
past.