I wanted to add that I'm mainly interested in types with interesting foliage, i.e. variegated, or burgundy, etc. I read at Jan's Country Garden website that she uses leaves in cut flower arrangements and I would like to do that.

Florida Hill Nursery says on their website that "Each Canna I offer is Hybridized and grown from tissue cultures to be a disease free exact replica of the mother plant."

Has anyone ordered from them?

Here is a link that might be useful: Florida Hill Nursery

Will cannas grown from seed be virus-free? I noticed Park offers several cultivars of canna seed. Will these come true?

Here is a link that might be useful: Cannas: Park Seed Catalog

The "Tropical" series of cannas are sold as packets of seed. These were developed as a seed strain/line and the offspring produced are physiologically the same as their seed parent. They are not "clones" of each other. You may see slight variations between individual plants but for most practical situations they are excellent. Start your seed early in the season.
Most seed generated offspring will be virus free but there have been exceptions noted.
C. Australia does not produce viable seed so it must come from rhizome division or tissue cultured material. Providing the tissue cultured material has been virus indexed and not been infected sometime after the fact it will be clean.
Always keep in mind that any seed produced from our hybrid cultivars will not breed true. I have never received virus infected plants from tissue cultured suppliers but that does not mean those plants will remain virus free if infected from some other source.
Florida does have an excellent TC lab for many of the cultivars listed by your link to Florida Hill Nursery.
Kent

Most Tissue Culture labs can not guarantee disease free plants. Propagation material is harvested from the most actively growing shoots of the stock material before going into the lab. This part of the plant has the least amount of infection, but it is still infected. Then it is multiplied, divided and last transplanted into the greenhouse to grow up into a young plant. These plants appear clean the first growing season, but usually show symptoms the second year. You can not 'cure' canna virus once it is inside the plant tissue, only delay the symptoms. At this point the only way to grow truly virus free Canna is from seed, or buy purchasing plants grown from seed. The tropical series has been out for years, the Rose won an AAS award back in the 90's. More recently was released a Bronze leaf/ red flower in the series.

Here is a link that might be useful: Park seed catalog

Just a brief follow up to the above post; I cannot speak for "most tissue culture labs", but I have grown a few thousand virus indexed plants from a lab (FL.) that are virus free. The few labs I am familiar with have been able to produce virus free offspring from contaminated parent plants. Depending on the type of virus infection (it is typically more than one) the procedures and protocols involved may change to help insure the offspring are virus free. Once a few offspring are proofed to be virus free they use the clean stock to continue the TC production. This is only one scenario and I am sure there are other possibilities. Of course, the simplest solution for any grower or lab is to have clean stock to start.
Growing cannas from seed will typically produce virus free plants (to the best of my knowledge), but it cannot be an absolute given. Most viruses are RNA linked but the badnavirus CYMV is DNA linked. This may be a sticky point. A few growers over the years have reported virus infection in seedlings. We really need to further explore this possibility.
The real problem with growing from seed is that one cannot grow any of our very best and most beautiful cultivars.

Kent

The cannas I got from Brent and Becky, and from Florida Hill in the spring of 2011, still show no signs of virus. I'd order from either one again, but they don't have a long list - FH has maybe 20 varieties and BB fewer.

The ones at our local upscale garden center - atrocious. Luckily they're close to two miles away.