The traditional Haggadah preserves some customs from when the Temple was still in existence in Jerusalem. All formal dinners began with an appetizer. Karpas is the appetizer of the Passover meal. It may consist of any green vegetable: parsley, lettuce, endive, cress, even scallion. 

The green vegetable is a symbol of springtime and the miracle of natures renewal. At this season, when Mother Earth arrays herself anew, the human spirit rises, and we renew our faith in a world where freedom and justice will prevail. 

The salt water, into which the Karpas is dipped, has been interpreted as salty tears, to remind us of the tears shed by the oppressed Israelites.

We recite:

בָּרוּךְ אַתָּה יי אֱלֹהֵינוּ מֶלֶךְ הָעוֹלָם, בּוֹרֵא פְּרִי הָאֲדָמָה

Baruch Atah Adonai, Eloheynu Melech Ha'Olam Borey P'ree Ha'Adamah.

Blessed are You, Lord Our God, Ruler of the Universe, Who creates the fruit of the Earth. 

haggadah Section: Karpas
Source: JQ International GLBT Haggadah