In what way might the rush leaves be symbolic of the speaker's love in "Thick Grow the Rush Leaves?"
The poem "Thick Grow the Rush Leaves" is found in The Chinese Book of Songs (The Shih Ching) by Kong Qiu. The poem is about the speaker's search for her love (the speaker is assumed to be female given the poem refers to "that man I love").
As for the rush leaves, one must know what rush is to interpret their symbolism/meaning in the poem.
Rush is a plant which thrives in shady and moist areas (normally found near lakes, streams and rivers). The leaves of the plant are used to weave baskets, seats for chairs, and mats.
That said, the symbolism for the rush leaves may signify the coming together of the speaker and her love (symbolized by the typical intertwining of the leaves). The rush leaves are described as being green (most likely too young to be used to weave). The speaker may be referring to the leaves as being green because her love is new as well.
In the second stanza, the speaker refers to the leaves being thick. This could symbolize the problems the speaker is having finding her love (perhaps her view is blocked by the thick leaves of the rush plant).
The last stanza refers to the leaves as being sweet. Again, the speaker could be referring to the love between herself and her love as being sweet (metaphorically determined by the symbolism of the plant).