All 'Chojubai' are Japanese flowering quince. But Japanese flowering quince is a common name for a group of species and hybrids in the genus Chaenomeles. There are many named cultivars of Chaenomeles only one of them is 'Chojubai'. The horticultural requirements of all Chaenomeles is pretty much identical. So what is said about 'Chojubai' pretty much applies to all of the rest. My personal observation is that small leaved cultivars are slightly less winter hardy than larger leaf, larger growing cultivars. Though in theory, when planted in the ground, all species are hardy through USDA zone 5, or able to withstand winter cold to -25 F or -32 C. That is planted in the ground. In a pot, and above the ground, hardiness is not as robust. Mulching in, or wintering in a sheltered area is recommended for those in small pots or fine bonsai pots in order to prevent pot being broken by freeze thaw cycles.
'Chojubai' is a specific cultivar of Chaenomeles usually considered C. japonica some consider 'Chojubai' to be C. speciosa. The distinction between different Chaenomeles species is difficult for non-botanists. And unless there is a clear provenance to wild collected specimens, it is not clear which cultivars of Chaenomeles are representative of true wild species and which are actually man made hybrids, and possible man made hybrids that escaped back into the wild. The work around is to use the genus name Chaenomeles and skip the species name, and finish with the cultivar name 'Chojubai', or 'Hime' or 'Toyo Nishiki' or what ever cultivar name you are dealing with.
After about 1975, commercial nurseries world wide were encouraged to adopt the convention that a name in single quotes would represent a single cultivar. That essentially all plants labeled with a cultivar or clonal name would be genetically identical.
In older literature sometime what looks like a cultivar name might represent a group of similar clones with similar traits, often representing a single batch of seed or a collection of plants from a specific geographic race of a species. This was the case with early 'Chojubai', where as pretty much all more modern named cultivars really do represent a single clone. 'Double Take Scarlet' is a single clone of a medium to large growing flowering quince. 'Chojubai' is old enough that there are a few different clones or cultivars trading around under the same cultivar name. This is why there is talk of 'Chojubai' with dark red, 'Chojubai' with orange, and 'Chojubai' with white flowers. One trait in common for all 'Chojubai' is the development of thick corky bark at an advanced age. Usually by 20 to 30 years most of the branches will have this corky bark. If it does not develop the corky bark it is NOT 'Chojubai', as this is the defining trait. There are dozens of nice dwarf growing Chaenomeles that are not 'Chojubai' that are very desireable as bonsai, for example 'Hime' and 'Kan Toyo'. None of the others will develop the corky bark.
Your photos are of a nice dwarf type flowering quince. I don't see any corky bark, if these are over 30 years old, then they definitely are not 'Chojubai', if they are under 30 years old, they could be 'Chojubai' or they might not be 'Chojubai'. You just can not tell. This is the reason that if a seller is asking a premium price for 'Chojubai' that they have some track record that they are good with provenance. I would never pay a premium to some random Ebay seller for a young looking flowering quince because they could label any young quince 'Chojubai' and one would have to wait 20 to 30 years to prove the provenance. Other cultivars of Chaenomeles are great for bonsai. 'Chojubai' is not the only one out there, it just that people get excited about the corky bark, which does not occur in other Chaenomeles.
also did I do a decent job on the styling you think?
