What kind of broccoli are you growing?

Some varieties produce large heads then smaller ones, some produce many smaller heads from the get-go.

The heads will look like the broccoli in the grocery store produce departments, maybe not as large, but green with tight buds (that become flowers if you wait too long).

The florets are the buds on the heads that swell as the plant grows and eventually break open into flowers.

Don't know the exact type. Got them at a nursery and at the time didn't know to ask.
The head has started to seperate and is no longer really tight. No flowers yet. Is it still good?
If I did wait until it started to bloom would it be edible?

Sounds as if it would be good to pick now, as long as the heads have small green floret nubs. Sometimes a larger head will separate into smaller ones before it flowers (they'll be yellowish) as it grows since the stems below the heads are branched.

Enjoy! It's fun eating the first garden goodies each year. I'll still have to wait. All that I have out are onions and lettuce, both too small to pick.

Most people don't like broccoli after the florets open, say it's tough and bitter.

So is the "proper" time to harvest the head whenever I think it is large enough but before the florets start to separate and grow out?

Example here is an Early Dividend that should have been cut yesterday. Notice the hint of yellow. another day and the flowers would strat to open.
{{gwi:8918}}

I'm growing broccoli for the first time too, and just like you I wasn't really sure when it was ready to pick (this was last month, zone 8), but I think mine started to seperate a bit, sort of like your description, before it bloomed, so I picked it, and it seemed fine.
So, I'm a newbie too, so you don't have to act based on my experience, but (in my humble opinion) now seems like a good time to pick it.

Yes, you can harvest it any time after the heads develop. Maybe the "Harvest" information in the link below will be helpful. To get other or confirming information Google "broccoli harvest" and you should find several articles describing when broccoli is ready and what it looks like.

Here is a link that might be useful: Growing Broccoli

I guess someone should mention this. Dont cut them off at the ground. Just cut off the heads they will sprout multiple smaller heads.

mine has a purpeish color to it so is it to early or to late to harverst and enjoy