We've grown both Tetra White and Virgo. Virgo may dry just a bit whiter than Tetra, but for us both are more a creamy white than a pure or silvery white -- but not what we'd call brown. The flower heads on Virgo are larger, but there are fewer of them per stem and the stems are shorter and the plants don't seem as vigorous overall, but we haven't grown it as long or tried as many things with it yet.

Our best luck so far has been when I've started seeds in the summer, planted out in the later summer. I did that year before last. Then the plants (Tetra) took off the following spring and give us our first harvest of the year, then kept going. We'll see if those plants continue to produce well this year. I suspect they won't, so I started another batch of seeds last summer and put them in a different spot. If the original batch comes on strong, that will be fine, if not, I'll rip them out and replace them. We've got some Virgo overwintering, as well, and will see if they are more productive in their second year.

We don't dry these in water. We hang them upside down in the loft of our barn, where it gets pretty hot and things dry quickly even when it's fairly humid.

Thank you for your help, Neil. I'm not sure why my feverfew is turning so dark. I knew they were supposed to be a creamy instead of a stark white, but mine are similar to the color of tea-dyed linen, which looks dingy and unattractive. They start out creamy, but gradually get darker. They're stored in an attic, which is dry & warm. I tried ordering from suppliers to see what theirs looked like-1 bunch was even darker than mine, another was a creamy off-white. I'll try varieties you mentioned, and see if there's a difference. I really need them because there's not that many other white-cream fillers, and they hold up so well. Also, they were one of the few plants that kept going last year in the horrible drought we had.

Another thing to try is Ammobium alatum -- winged everlasting. It has a ring of very double "ray flowers" (that may be bracts) and a yellow center and it's about the size of feverfew. There's usually just one or two flowers per stem, but the plants start producing early and continue all summer. The white dries really white and stays white for a long time, ageing to cream. If you pick early, the yellow center isn't exposed, but the overall effect isn't bad even if the center goes past yellow to a dull gray.

The dwarfish "Bikini" variety has been the most widely available but even it seems to have disappeared from a lot of catalogs. J.L. Hudson has the regular variety, though, and that's what I've grown.

We're harvesting feverfew and other things now, and I've had a chance to look at some of our older things and have to amend what I first wrote.

First, setting out young plants one summer or fall for harvest the next year seems to be the way to go, but the plants do not come back reliably the next year. They behave more like biennials than perennials.

Second, Virgo actually dries to a creamier color than Tetra White, which starts off as a quite white dried flower, but does turn to beige in the course of a year.

Alternate white fillers, in addition to ammobium, are achillea and statice. Nurseries usually sell colored forms of A. millefolium these days, but the wild type is easy to transplant (and potentially invasive). Also expansive in the garden is A. ptamica, "The Pearl," which has small, tight heads (but a lot of them) vs. the broad heads of regular white yarrow.

"Iceberg" is a white Statice sinuata (Limonium sinuatum) in the Pacific series available from Stokes that is a very useful filler -- so useful, that I order twice as many seeds as of the various colors offered.

"German statice" -- Goniolimon tartaricum -- is nice, but I have difficulty keeping the plants alive for many seasons, and they're slow to start from seed.

Thank you for the update, Neil. I was pleasantly surprised that all but a few of my feverfews came back this spring, after a drought last summer and too much rain this spring.
I've noticed that the feverfew I dried in water last year retained its whiteness for a pretty long time, but eventually turned the same color as the air-dried ones, so doing them that way probably isn't worth the trouble. I like A. "The Pearl", too, but the feverfew is a little sturdier. German statice didn't do well here, either-glad to know it's not just me. Thanks again for your input.
Sylvie