Hi kathleenkelly
You are welcome
No, you dont have to do that.
If you open your yellow tool box you will see the brown sprinkler to water flowers, and the highest size sprinkler you own at that moment.
In your case as the purple one is missing, you should see the brown and the green sprinklers.
You should be able to irrigate crops, trees and flowers, double grow speed and extend waste time in every farm you use it.
If you are not sure if you can irrigate or not the farms, you can click in the yellow tool box, then click in the clock and then in Per farm option.
The farms with green ticks are the ones you can irrigate, the farms with a time, if you hover your mouse on it then you will how much time you have to wait till you can irrigate again.
Please take in mind you can irrigate a farm every 20 hours, so if you plant let say beets and irrigate, then if you harvest then after 2 hours, and plant for example wheat, it will not be irrigated as you will have to wait 18 hours to be able to irrigate again.