P. parviflora is the correct nomenclature, pentaphylla has floated in Bonsai books or in describing putative hybrids. However, I think if you look at enough of the contemporary Kokufu books, you will see the same trees described as pentaphylla before and parviflora later. Isn't taxonomy fun? When I was taking Mammalogy in college, the Professor, Ken Geluso always liked to show E. Raymond Hall's Mammals of North America text which included at least dozens of species/sub species of Bears in North America based on any number of characteristics, the next Hall book that came out in the early 80's had only  the three North American species we now know (Black Bear- Ursus americana,  Brown Bear (aka Grizzly) Ursus arctos; and the Polar Bear Ursus maritimus), taxonomy frequently throws us curve balls based on folks initially describing variable individuals of a single species as different species, over times these things get corrected.

I recommend this looooong and highly technical article entitled: "White Pines of Japan" if you are still interested in knowing the difference between Pinus Parviflora and Pentaphylla.


http://www.fs.fed.us/rm/pubs_other/rmrs_1972_bingham_r001/rmrs_1972_bingham_r001_179_199.pdf

"Pinus Parviflora Complex"

The classification of pines with five needles per fascicle has been discussed in length and still puzzles taxonomists. N.T. Mirov who has studied these pines, as well as others, states in his monograph The Genus Pinus, that the reclassification of Pinus parviflora should be studied further.

In my second book, The Encyclopedia of Classical Bonsai Art, Volume 2, Japanese Five-needle Pine, Nature, Gardens, Bonsai & Taxonomy, I basically said that some taxonomists have split Pinus parviflora into two separate species, Pinus pentaphylla (which is northern) and Pinus himekomatsu (from the south). Two famous plant explorers, Philip Sielbold and Joseph Zuccarini originally described and classified the Japanese five-needle pine as Pinus parviflora in 1842. Other explorers have also studied this species and slit them into the two other species.

But we are generally growing Japanese five-needle pine, Pinus parviflora for bonsai. In the horticultural world the name Japanese white pine is used commonly used for this species. However in the bonsai world we generally use the name Japanese five-needle pine since it is closest to the Japanese translation of "goyo matsu" (pine with five leaves).

Not to make things more difficult, but there are also a few other pine species with five needles per fascicle native to Japan. Japanese stone pine, Pinus pumila is sometime trained for bonsai in Japan. The others are rarely trained for bonsai in Japan.

By the way, in Japan the bonsai artists do not care if Japanese five-needle pine is a Pinus parviflora, Pinus pentaphylla or Pinus himekomatsu. They just call this species "goyo matsu". It is important to realize that most of the Japanese bonsai artists do not have the background, nor interest to discuss taxonomy. They are only interested in training and growing bonsai, as are most of the bonsai artists around the world.

Hope this helps,
Bill

PS: My pine book as well as Volume 1 on propagation techniques used to create bonsai have long been out of print and are difficult to locate.

I found this old thread while looking around at JWP stuff, I had noticed that NEBG has a couple JWP that they are specifically listing as pentaphylla, and wondered at the difference if any.  They only list a few out of their JWP stock as this variety. 

They are grafted, but they are labelled differently than the other grafted JWP's.  Here is a link to the page... there are 2 towards the bottom that are listed as pentaphylla.
http://www.nebonsai.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=NEBG&Offset=30&SortBy=name-asc&Category_Code=BON