This is my first year growing much garlic. I grew a couple of plants last year, but this year I did about 8 types from a variety pack (I would have to go out and check the tags to see what they are.) I've been looking things up like crazy to figure out when they're ready to harvest, what to do, etc. I can't vouch for all of the following form my own experience, but wanted to share some of the bits of research that I found helpful -- I'll focus on the scapes-related stuff since that's what the thread was originally about.
- after scapes appear, it's about a month for the bulbs to grow and mature to their full potential
- the degree to which leaving the scapes to form bulbils will make bulbs smaller depends on the richness of your soil. In good soil, it could be only a 5% size difference. In poorer soil, it's a bigger difference.
- the curliness of the scapes is supposed to be similar within a variety - e.g., Turbans have a U shape, Rocamboles a double loop, etc.
- harvest when about 60% brown/yellow foliage and 40% green. Don't wait till it's all brown, or the outer skin may burst (this one I can vouch for, having had some of my Turbans burst the skins and almost end up naked. Scrubbed off all the cloves and that's what we'll eat first.)
- Lots of places say to turn off the water for the last two weeks to let them dry out a bit before harvest. Better to stop too soon rather than too late.
Here are a couple of the links I found helpful:
http://www.hoodrivergarlic.com/garlic-calendar.htm - helpful for having actual pics of what the foliage looks like when they harvest
http://www.gourmetgarlicgardens.com/ - I found the thing on scape characteristics here in the Asiatics information
http://www.garlicfarm.ca/growing-garlic.htm - good general info
And, as a proud newbie, here's a picture of my early garlic: