This medium size (19 inches high by 60 inches wide) species of hostas from Japan has an intense white bloom on the bottom of the pie crust shaped leaves. The striped flowers are medium lavender and appear from mid-August into September followed by viable seeds.

According to The Hostapedia by Mark Zilis (2009), "Since H. pycnophylla is native to only a few Japanese islands, it is remarkable that it has become such an important breeding plant...Traits that H. pycnophylla seedlings exhibit include recumbent scapes, white floral bracts, an intensely white bloom on the leaf underside, and good marginal rippling."

In the The Genus Hosta by W. George Schmid (1991), it states that this species was discovered on mountain ridges. The epithet means "densely arranged leaves".

The New Encyclopedia of Hostas by Diana Grenfell (2009) states: "A superb parent for white-backed, ripple-edged hostas and now the pod parent of a superb, thick, yellow-leaved hybrid, H. 'Aliyah's Grace'. Wild specimens are much smaller than those in cultivation, although it is not an easy hosta to grow, seeming to dwindle rather than increase."

Mark Zilis' Field Guide to Hostas (2014) states that this species was found in Japan in "...woodlands..."

An article by W. George Schmid in The Hosta Journal (2002 Vol. 33 No. 2) states that, "Among the most remarkable species is H. pycnophylla. Bob Olson would call it "a white-backed-leaf little devil-to-grow plant." Despite how difficult it is to grow, it has become a favored source of genetic material because its leaves have a very chalky white back. It is rare in the wild and not east to find or get to.

...1) In the South, H. pycnophylla needs mostly morning sun in spring and shade in summer...in the North, it needs more sun than shade all day in both spring and summer. This species is very shy about flowering if it does not get enough sun...2) As with all relatives of H. longipes, the plant does best if you supply plenty of water...particularly during summer drought periods. 3) In the North, plant this species in an open location facing south or southeast to gain additional growing season...since this is a southern, long-growing-season species that requires plenty of moisture and warmth (even heat) to flower and set seed."

An article by Warren I. Pollock in The Hosta Journal (2003 Vol. 34 No. 1) states that, "H. pycnophylla, the pollen parent of 'Cutting Edge', was named by Dr. Fumio Maekawa in 1976...The green leaves which can be as large as 8 inches long by 7 inches wide at maturity, have slightly rippled margins and white undersides -- from which 'Cutting Edge' gets its principal handsome attributes.

The Hosta Journal, (2006 Vol. 37 No. 2), in an article about flower characteristics stated that this species has "...nearly horizontal scapes with the full weight of the blooms..."

An article by Warren I. Pollock in The Hosta Journal (2014 Vol. 45 No. 2) states that, "H. 'Liberty Bell' crossed with ('Urajiro Hachijo' × H. pycnophylla) is a favorite pod parent of Don's (Don Dean). He used it to produce H. 'Celtic Bouquet' and H. 'Peek-a-boo Purple', both registered in 2011, and H. 'Ebony Towers' and H. 'Garnet Spires', in 2005. (Special Note: Parentages of 'Garnet Spires' and 'Peek-a-boo Purple' were corrected in the 2013 Registrations issue..."

Mikiko Lockwood in an article on The Hosta Library titled, A Little About Japanese Hosta Terms defines the term urajiro as white-backed or white underside.