This is wrong.
Rows of healthy tall sunflowers filled the field
Comma after healthy and sunflowers
The others are correct.
Read the sentenced Add commas when they are needed.
I wrote the letter folded it and mailed it.
Comma after "letter" and a comma after the first it
Justin prepared the soil planted the seeds and watered the garden
Comma after soil and seeds
Our dog ran across the lawn through the gate and into the street
Comma after lawn and gate
Rows of healthy tall sunflowers filled the field
Comma after healthy and sunflowers
The deep cold lake looks refreshing
Comma after deep
5 answers
No comma after sunflowers?
Right -- no comma after sunflowers.
Can you explain why?
We don't usually put a comma after a prepositional phrase.