Certified GKH Gardening Expert
Late spring and summer are ideal planting times for sunflowers and they enjoy being located in areas with full sun. Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/flowers/sunflower/growing-sunflowers-in-your-garden.htm
I am in zone 5, I buy seeds, there are a variety of kinds, I plant at May 24 weekend when no chance of frost. They need full sun, I put them at the back of my garden, they are huge by august into september. Once we planted them in a circle and made a house by tying the tops together like a teepee. Lots of water is required.