You can get good calendula flowers in bulk from the UK.
Pic: Bought vs. picked calendula flowers.
Here's a pic of two different batches of Calendula flowers:
1) Organic herb trading co. dried herb, from Spain, and 2) mine.
You can see that my calendula flowers are a little brighter, especially in the orange and green parts. But for bought calendula this is excellent quality: the color difference is small, and the smell of the bought flowers is not too bad. Nice!
I'm making another batch of calendula salve as I write this (earlier this week, as you read this), with the bought herb.
I'll be getting year-old calendula from a local pal in January; I'll put up a three-way comparison of color then.