It is not possible or necessary to use all of the plants found in the gardens of Japan. Using Japanese plants does not make your garden a “Japanese Garden.” Rather, it is best to find locally available plants, match them to the site, and strategically place them in the garden to fulfill the proper role.
Korean boxwood is one such plant that is locally available, seems to be very hardy, is green throughout the year, and fulfills the important role of tamamono or O-karikomi. That is, low plantings grouped in large, wavy masses, or individual semi-spherical shapes. See Azaleas in Japanese Gardens for similar discussion on these roles.
Korean boxwood works well in this role because they naturally tend to form low, round masses. They also seem to be fairly versatile when it comes to site requirements like sunlight/shade. Another attractive aspect of this plant is that it is deer-resistant.
There are many cultivars available in nurseries in the New York/New Jersey area. No plants are guaranteed to be pest or disease resistant. And the health of the plant also depends on proper installation and annual care. It is best to consult the nursery and/or local landscape professionals when choosing plants. Some cultivars I have used successfully include Boxwood ‘Winter Gem’, and ‘Wintergreen.’ They offer a deep, rich green throughout the year.
Over many years even korean boxwood will attain some height, but the ideal use is in masses or semi-spherical shapes, about two to three feet high. This will, like all planting, require some annual maintenance like one “true” shearing, and then a couple of touch-up trimmings. The best way to do this is with a pair of high quality shears for the “true” shearing, and hand-snips for touch-up later in the season, although to some extent it is a matter of preference.