Why are my sunflowers not blooming?

Well watered and fertilized! Guess you answered your own question. Birds and Bees time. Plants flower for one reason to pass on progeny, to get seeds they need to flower so bees pollinate them and seeds form. Seeds form and make new plants. If you baby a plant it feels it will live forever and doesn't bother to flower, too much work. Sunflowers like it dry and poor soil. That is why they do so well in the wild where no one is Fertilizing and Watering them Well!

There are dozens of different varieties of sunflower. I have five growing this year. All have bloomed except the "Mongolian Giant". This is the most likely explanation. Garden plants and vegetables love to tease us. I only got my first ripe tomatoes last week and my melons are still weeks from being ripe. Patience is the first thing you need to develop to be a gardener.

You also could be preventing blossoming by fertilizing them particularly if you are using chemical fertilizers. This is one of the main causes of delayed fruit set in tomatoes when it comes to amateur gardeners. I found this out the hard way. I now use only organic fertilizers and pesticides. I rarely fertilize after plants have been transplanted into the ground. I use only compost and other organic fertilizers from Espoma, Jobes and a select few other companies. Organic fertilizers are all "slow release" and won't do nasty things like burn the roots, you, poison beneficial wildlife such as toads or build up chemical salts in the soil.

Maybe you planted them late.

Maybe they aren't getting enough sun.

Do they at least have heads on them where they will blossom?

I've always had sunflowers in my community garden and so far we only have one with a flower on it. They can often not bloom until September.

Lestermount