The most popular and certainly the most unusual Japanese holly cultivars is 'Sky Pencil', seen here in the Children's Garden at the Atlanta Botanical Garden (circa 1999).
Here a single 'Sky Pencil' plant, trained into a fan shape against a trellis, is ready to be espaliered against a wall.
In the wild, the species, Ilex crenata is an extremely variable shrub or small tree. Typically, Japanese holly grows as a dense, compact, evergreen shrub with small (1 in; 2.5 cm long) evergreen, oblong or elliptic, leathery shiny dark green leaves that have crenate or serrate margins. The tiny white flowers have four petals and give rise to glossy black pealike fruits about a quarter inch (62 mm) in diameter. Flowers and fruits are inconspicuous and not particularly showy. A maximum height of 10-15 ft (3-5 m) is possible, but most popular cultivars rarely exceed 3 or 4 ft (1 or 1.2 m) in height. Several botanical varieties, differing in stature, habitat, or morphology are recognized from throughout the species' wide range in eastern Asia, and many of these and their hybrids are the basis for numerous horticultural selections.
The various forms of Japanese holly are popular landscape shrubs and there are at least a few dozen named cultivars in the trade. Cultivars include low, spreading plants suitable for ground covers; compact dwarf shrubs for specimens or hedges; tall pencil-like novelty trees; and shrubs with a weeping habit; as well as plants with variegated foliage, tiny leaves or yellow berries. 'Sky Pencil' is a strange looking selection that is fastigiate, which means it grows in a narrow vertical shape with all the branches pointing upward. A specimen 6 ft (2 m) tall will be only 12 in (30 cm) wide.
Location Ilex crenata is native to Japan, China, Korea, Russia and the Philippines. The species occurs in a variety of habitats, wet and dry, open and forested, from near the sea coast to up in the mountains.
Light: Grow Japanese holly in full sun to light shade. Variegated cultivars do better in full sun. Moisture: Japanese holly grows well in most soils (but does best in acidic soils) as long as they are not waterlogged. Supplemental watering should be provided to newly planted individuals and during severe droughts. Hardiness: USDA Zones 6-10. Some cultivars may be hardy to zone 5. Propagation: Seed may be sown in autumn, but germination can take 2-3 years. The best way to propagate Japanese holly is by cuttings. Use young, fast growing tip cuttings under mist in spring or semi-ripe cuttings in summer. Some of the more exotic cultivars are normally grafted onto seedling rootstock.
The Japanese holly's small leathery leaves make this species an excellent choice for compact sheared hedges and bonsai.
Usage Ilex crenata is used in formal hedges, as specimen plants and in mixed borders. They are frequently used as neatly trimmed hedges along building foundations. Japanese holly is often used for bonsai. The cultivar 'Sky Pencil' makes an interesting vertical accent for a small space or corner in the landscape, and a line of them could also be used for a screen or narrow hedge. Japanese holly is quite similar to boxwood (Buxus microphylla) and yaupon holly (Ilex vomitoria), and is used in the landscape in the same ways.
All of the hollies are dioecious, with separate male and female plants. Only female plants produce berries, of course, and their flowers must be pollinated from a nearby male plant. 'Sky Pencil' is a female clone, as are many (but not all) of the named selections.