"Sustainable" in a poem

As I have mentioned previously, April is National Poetry Month and also Mathematics Awareness Month -- and the mathematical focus is "Mathematics of Sustainability."  To try to connect these April celebrations, I went to the website  www.Poets.org  and searched for a poem containing the word "sustainability."  There I found  "Patience" by Kay Ryan which contains these lines:

       Who would
       have guessed
       it possible
       that waiting
       is sustainable —
       a place with
       its own harvests.    

Please go here to Poets.org to read Ryan's entire poem.