Delta Sunflower helianthus annuus
Every year I buy a couple of sunflower seedlings from Annies Annuals as a treat for the bees. I have never had luck growing a sunflower plant from seed because as soon as it would sprout to about 1 inch tall, something would bite them and the sprouts looked as if they were snapped in half. I suspect cutworms, but was never sure.
So it's a lot easier for me to buy the seedlings that are about 5 inches tall. I just re-pot them into large plastic container pots, and then they shoot up in height.
I only buy the native sunflower varieties, such as the Delta Sunflower pictured above. I bought that one last year and it bloomed through September. It branched out with a lot of stems and flowers, so it was wonderful to observe, especially as a main plant to count bees for the Great Sunflower Project http://www.greatsunflower.org/
I've also had success with Lemon Queen sunflowers.
Sunflowers are a great resource for pollen and nectar for bees. In the Bay Area they mainly attract honey bees. But there are casualties too because of the crab spiders that take on the color of their host flower, and sit and wait for the unsuspecting bee and can instantly attack and immobilize them. Sadly I discover every year a few victims of the spiders. I am constantly knocking down silky spider threads that form traps in our garden to try to protect the bees.
A couple of weeks ago I bought two sunflower seedlings, a Lemon Queen and a Mammoth sunflower. I transplanted them to larger pots and put tomato cages around them to help stabilize them as they grow taller.
You can imagine my shock a few days ago when I discovered the Lemon Queen plant broken in two! I think one of the plump squirrels that visit the garden sat on the plant and damaged the plant. Maybe the plant will still survive and produce several smaller stalks. I hope it does!
Damaged Lemon Queen sunflower plant.