How many years does it take before a crappie can mature?

As long as it takes for hair to start growing under his pits.  

As long as it takes for hair to start growing under his pits.

Now that was one of the best answers that I have read on this board...

I would have to lay my bet on teh 2 1/2 years mark

For what it's worth it seam it base on who you ask: See Below

Sexually mature usually at age II or IV.

http://www.bio.txstate.edu/~tbonner/txfishes/pomoxis%20annularis.htm

Age at maturation: In Texas, some individuals mature at age 1 (Carlander 1977);

In Illinois, maturity was reached by 2 or 3 years (Hansen 1951).

http://fishresource.com/fish/fish010.asp

Mature crappies (2 to 6 years old)

http://elib.cs.berkeley.edu/kopec/tr9/html/sp-black-crappie.html

Black crappie become mature in 2-4 years;

The maximum life expectancy has been reported as 8-10 years (Scott and Crossman 1973).

great links