Some of the best? I guess that's just a matter of opinion. I don't find them to be as floriferous or have as wide a color selection as say the 'Sunshine' strain or producing as upright a flower as the 'Winter Queen' strain and in my climate, they are inevitably prone to botrytis and leaf spot. So no, they are not on the top of my list. I actually prefer those plants that are offered by specific color, like the Mardi Gras or Heronswood series - more intense and wider color selection and better markings as well. These have been developed by west coast breeders and may not have as a wide a distribution (and who knows what Burpees will pass off now under the Heronswood name).

Seed strains do offer a great deal of variability within them, so it is quite possible that one of your plants is showing characteristics unlike its cousins. The parentage of xhybridus is extremely diverse and that specific plant may be displaying some more recessive genes. Or it could be mistagged. Difficult to tell, especially by description.

Does it really matter if it grows and flowers well for you?

I purchsed several of the RH Strain years ago, when they were first introduced by John Elsley, then VP & Head Horticulturist at WG. (Now at Song Sparrow / Beaver Creek).
They were selected for flower color only and the foliage will be typical of X hybridus. The claims of up to 5 months of flowering is overly optimistic, in my experience and that of the Kemper Centre at the MO Botanical Garden (MOBOT). It can be as short as 7 weeks and the longest period recorded by MOBOT was 17 weeks and they were not consecutive weeks.
Some growers complain that their RH plants are sterile and never produce viable seed. I've not experienced that with mine, even though there are a dearth of vectors about during the flowering season.
HD sells the RH Strain (labeled as such), but the flowers appear to me as no different than the ordinary X hybridus seedlings that I grow by the thousands (looking for those special ones!) .
My 2c
RB

1. They report that the Royal Heritage tm strain will bloom up to 5 months in some climates. Listed as USDA 4-8 and needing well-drained, moisture-retentive soil, and can even thrive in clay.

My nursery is on extremely heavy clay and whilst it takes a season for the plants to establish, after they have done so they do thrive. Well drained but moisture retentive soil - if anyone has this, I haven't met them! Hellebores will do OK in pretty much any soil. I've grown them in soil which is flooded regularly during flowering time and they are OK with that too. Don't believe all you read in the books or magazines. Most articles (at least in the UK) are written by literary prostitutes hired to write such articles - they are NOT experts on the genus.

2. Are these truely some of the best Helleborus x hybridus strains offered in the nursery trade today?

I agree with Pam. I would probably be a little more blunt though and say an outright no. Pine Knot are at the forefront and Northwest Gardens also offer superb plants.

3. I recently purchased three different ones that are supposed to be the Royal Heritage strain. One blooms almost black, and another blooms redish but later changes to an almost dark pink. both of those two produce stems and leaves looking rather greenish with slight suggestions of yellowish coloring on the just emerging leaves.

You are seeing the variability present in the H. x hybridus group.

4. The third plant purchased is supposed to still be from the Royal Heritage strain, but the coloring and texture of both that plant's leaves and stems look entirely different. supposedly, the blooms of this plant will emerge green and fade to white. But the leaves currently appear to be an almost gray to blue shade of green and the leaf stems are red.

As above.

5. The drastic difference in the appearance of my 3rd plant makes me wonder if it really is part of the Royal Heritage strain.

I detest the use of the word strain in relation to hybrid hellebores. Not a dig at you at all, Katrina. It doesn't make any sense. One 'strain' generally isn't distinguishable from another, so the term 'strain' is rendered useless.

6. Does such stem and folliage coloring differences truely occur in RH strains, or is it more likely my red stemmed plant is not true to its Royal Heritage tm Stain Lenten Rose nursery label?

It occurs in hybrids grown all around the world. Forget the name and enjoy the plant.

Pam, I've enjoyed you recent posts - you are a breath of fresh air. Are you expecting a good spring with your hellebores next year?

Hi Tim - good to hear from you! Always a good spring for hellebores around here :-) I'm very pleased to have some blooming stock in at the nursery right now - some big, beefy Heronswood doubles and a few quart sized RH blooming as well (hey, if they're in bloom, they sell - I don't much care about the provenance :-)) Plus, all the foetidus are budding up nicely - they are typically the earliest to bloom around here but the x hybridus have been behaving oddly this season and I've had some blooming since early in the fall.

I buy almost entirely from local growers and for some reason, no one here carries any Pine Knot plants. There are a lot of very excellent hybridizers and growers in the area and I am never short of great offerings. But I keep hearing good things about the PK's. But truth be known, x hybridus is not my fav of the hellebores by any stretch of the imagination. I much prefer the nigercors or ericsmithii type hybrids.