Need a lot more information:
1) Was your car parked in front of a private residence, apartment, townhouse, commercial property, what???
2) Who authorized the towing? Property owner, city???
3) Were there any posted no parking or towing signs?
4) Was the towing done to enforce local (city, county or state) laws?
5) What reason were you given for the tow??
6) Does your community have a 'cars parked on grass will be towed' law??
Without these facts, any answer you get would be pure speculation.