You harvest as soon as the head is large enough for your use. Cauliflower heads very rapidly 3-5 days, so you have a short harvest window. Most varieties are fairly uniform so just over a week between first and final heads. A little slower in winter. I cut my first head last week and the last of 18 plants needs cutting now.
{{gwi:12598}}

I'll tell you a funny story that's off topic. Two summers ago (2013) I grew some Purple Cauliflower. I knew I was growing Cauliflower, and where it was. So I was looking at my Cauliflower one day, and saw something very worrying. My Cauliflower was looking all pink and moldy. I didn't quite know what the cause was, but within a few days I decided I better compost them. It took me a while to realize that I was growing Purple cauliflower and that's why they looked that way.

Moral of the story, don't grow purple cauliflower if you don't remember they're purple. :)

Its something I find it hard to estimate as well. Last season I let it grow too long and the curd was brown and not so good. I am also trying to grow purple and orange cauliflower more because they taste almost the same but have higher nutrition content.

Here is a link that might be useful: Growing Cheddar Cauliflower

Wish I could find a head of cauliflower.

45 to 50 day maturity. Put the plants in the ground around mid-august and still no heads.

Grumble....grumble......

Hi Hobbiest, look for Snow Crown. The hybrid I have is 50dtm. Planted Nov. 1st here in Central Florida and almost ready to harvest...crazy considering the 80 degree December we had!

jennieboyer, I generally watch the cauliflower florets at the base of the head and look for separation. I try to catch it when they just start to separate. This is not always easy to see, especially for the self blanching cauliflowers...Below is a Candied Charm head that is noticeably separated.

{{gwi:2117843}}

Here is a Candied Charm head that is just starting to separate.

{{gwi:2117844}}

Here is a Romanesco Veronica head that is showing first hints of separation. Its a bit hard to see - look close at the bottom florets. I picked it because we are supposed to reach 20 degrees in the AM and I did not want to take a chance on an essentially ready-to-pick head This is my first year growing the Romanesco Veronica and I'm not sure of it's hardiness. I have several smaller heads and will soon know of their hardiness.

{{gwi:2117845}}
. But as noted above by farmerdill it's really a matter of preference.

grandad: those are just about perfect.. any more separation and one has waited too long.

Jennie: I wouldn't let FULL size interfere with harvesting a week or so prior to that potential. Better a week early than a week late. :

Kevin