應憐屐齒印蒼苔，

Perhaps being fearful of my clogs would step on the path of green moss,

小扣柴扉久不開。

no one answers the thatch door to my long knocking.

春色滿園關不住，

But the variety of spring colors cannot be locked up within the garden;

一枝紅杏出牆來。

a twig of sprouting pink apricot crops up over the wall. 

PS I got to know the poem when I was a HS student.  One day our teacher of Chinese language cited the verse of  "春色滿園關不住，一枝紅杏出牆來。" of this poem, and connected it with another famous one by Du Fu, "花徑不曾緣客掃，蓬門今始為君開。" (please see my translation at http://classic-blog.udn.com/kkuo0810/125139464) to make up a not-so-obscene dialogue between a newly-wed couple at the first night of their marriage.

Actually it is a poem of wisdom.  I love it, and I hope you do.