I'm fond of rhododendrons with a calyx that is the same colour as the corolla. Here are two in the Ted and Mary Greig Rhododendron Garden in Stanley Park. I think I have these named right - they are listed on an old Park Board brochure of 50 Rhododendrons of Interest - https://vancouver.ca/files/cov/ted-and-mary-greig-garden-50-rhododendrons-of-interest.pdf and shown on the map at roughly the same locations. Rhododendron 'May Day' Rhododendron 'Fabia'
If you like hose in hose flowers with the same colouration, keep an eye out for Genghis Khan Hybrid Rhododendron Plant Description Red flower with long red calyx. Of course when the calyx and flower are the same colour, they don't stand out against each other.
Thanks for the tip! I hadn't heard the term "hose in hose" until this year when I inadvertently learned it after figuring out that a R. 'Mother's Day' tag at VanDusen was on the wrong shrub, and a VanDusen volunteer used it in a reply to me. I found a description at HOSE IN HOSE, where it says (in French) that the term applies where there are two corollas, but it hadn't occurred to me that it applied here. So that means the calyx here is the very tiny green thing, and the "coloured calyx" is really an outer corolla? Your link for R. 'Genghis Khan' says "vivid red, calyx about 1" long".
Hose-in-hose typically refers to a colourful, petaloid calyx. Petaloid calyces are common in some rhododendron groups, including especially subsection Neriiflora. For example, Rhododendron dichroanthum is parent to a long list of hybrids with elaborated calyces, including Fabia Group, Hotei, Medusa Group, Jingle Bells, Buttermint, Genghis Khan, etc. There are also numerous examples in evergreen azaleas (e.g., Kirin), although these calyces tend to be more corolla-like.
I saw this again today, thought it was the most beautiful rhododendron EVER, until about five minutes later, but I still really like it. I photographed more detail this year, and now reading the description for 'Fabia' in the Park Board document, I see that the indumentum is supposed to be pale brown and trusses should have nine flowers. Is there more variation among plants in the Fabia Group? The indumentum here is almost white and the popular number of flowers seems to be five or six. Does it still qualify as belonging to that group? In the same document there is also an Alleyne Cook cultivar called 'Wedding Present', which looks lighter but is described as being "vivid red-orange", with no other description, but just a bit of a coloured calyx is visible. I can't find any other mention of that cultivar on the internet. It's such a drag that Hirsutum.info a virtual arboretum: all about rhododendrons, azaleas, azaleodendrons and vireyas photos have disappeared and the only contact info says "we don't read any emails sent to this address".
The Rhododendron 'Fabia' - Find Azleas,Camellias,Hydrangea and Rhododendrons at Loder Plants website says 'Fabia' has fawn indumentum, with their photo showing what I would call white indumentum, similar to these, so I think this is probably the right name.
Here is a planting at the front of a condo in the West End. I think this is R. 'May Day'. The largest leaves are around 8cm, which is consistent with a description I have seen.