Sunflowers are an incredible plant to grow! I always plant a small patch of them every year, as they are great forage for my bees, good feed for my chickens and the wild birds enjoy pecking away at them too.
Survival Of The Fittest, Not The Sh$%^Test - This is what mulch is for – it provides a home for insects, predatory mites, little wasps, and the plethora of things that are not there on commercial farms due to pesticide use.
This ensures the biggest sunflower heads and the best pollination, and honey production. If you look at the data for your area, find the warmest month, and count back 160 days from the middle of that month. That is when you plant your sunflowers.
The plants thrived but were disease-prone. They attracted all sorts of irritating things that damaged the leaves and caused mold, smut, and similar problems. I had a lot of problems with sunflower petals turning white.