plant a tree:

"An ancient and lovely tradition is to plant a tree when a new baby is born. According to the Talmud, in biblical times a cedar was planted for a son, a cypress for a daughter (Talmud Gitten 57a). The cedar symbolized strength and stature; the cypress gentleness and sweetness. The children cared for their own trees, and when the child was ready to be married, branches were cut from the tree to make the chuppah.

You can build on this custom by planting a tree at every birthday. Children can watch their "family" of trees grow. You can use the occasion to tell the story of Honi, the Circle Maker, the miracle worker of Second Temple times (first century BCE), who planted carob trees throughout Israel. Once when a passerby asked why Honi bothered to plant a tree that would take 70 years to bear fruit, Honi replied, 'As my ancestors planted for me, so do I plant for my children.' If you cannot plant a tree in a yard, arrange to plant one in the Children's Forest in Israel."

-Jewish Family & Life: Traditions, Holidays, and Values for Today's Parents and Children.
(Yosef I. Abramowitz & Rabbi Susan Silverman)