I believe it’s up to 10 plants brings the $250 fine, but may be mistaken.
Edited to add the language from the bill.
1. For possession of between five and 10 marijuana plants, (i) a civil penalty of $250 for a first offense, (ii) a Class 3 misdemeanor for a second offense, and (iii) a Class 2 misdemeanor for a third and any subsequent offense;
2. For possession of between 11 and 50 marijuana plants, a Class 1 misdemeanor;
3. For possession of 50 to 100 marijuana plants, a Class 6 felony; and
4. For possession of over 100 marijuana plants, a felony punishable by a term of imprisonment of not less than one year nor more than 10 years and a fine of not more than $250,000, or both.