Which two lines in this sonnet use symbolism to describe old age

The answer is:

And big deep trenches in thy beauty's field,

and

Will be totter'd weed of small worth held.

The deep trenches is a beauty's field is saying that an open field of life and nature soon became trenches from man for war. Therefore is aged.

Will be totter'd weed of small worth held means that the weeds always were alive on the field but now they died because they got old.

Hope this helped you on the question and in the future!

in this alternate universe, renaissance romeo is now seventeen, an apprentice to a glass maker in venice. modern romeo is planning to go to college. what major do you think he’ll elect?