Considering you are in Iowa, I'd say you are looking at at least 20 years for white oaks to produce and 10 years for sawtooths. I'm in southeast Pennsylvania, which is generally the warmest part of the state - I would think that our weather is similar to the mildest parts of Iowa. My oldest sawtooth oaks are at least 10 years old and still haven't produced. I'm hoping to get some acorns this year. Sawtooth oaks seem to take it really hard when it gets below 0 degrees in the winter or when you get a late frost.