there is no wrong time of year ... without a pic.. its hard to explain how ... with any specificity ..

with an annual... you dont have many options on delaying it ..

and when it displeases you .. then teach it a lesson ...

ken

That's what many typical petunias do in the summer. They languish in the heat. Cut them back pretty severely, keep them well fertilized, and they will rebound for you.

In the warmer parts of the country, petunias are treated as a fall, winter, and early spring plant.

They are tender perennials, by the way.

if its an annual for me in z5 .. it surely is for her in z4 ...

if you dont want a stark change ... take about 1/3 this week ... one third next week ... etc ...

this way you still have some flowers.. while other parts are resprouting ...

but then if its just so ugly ... do it all ... and then ignore it for a couple weeks.. while it sorts itself back out ... [do keep it watered, of course]

try to prune just above a new bud ... there are hundreds of them along the stem.. waiting for your cut to stimulate them into growth ...

i am pretty sure.. chicago is z5 ... but that doesnt matter ...

ken

I have twice tried to change it to zone 5 with no luck