Culture
Easily grown in average, slightly acidic, moist, well-drained soils in full sun to part shade. Part afternoon shade is best in hot summer climates. Best sited in locations protected from cold winter winds. Hollies are dioecious (separate male and female plants). Plant one male for every 3 to 5 female plants.
CASTLE WALL is a male clone that will not fruit. It serves as a pollinator for certain female clones including Ilex x meserveae ‘Hachfee’ CASTLE SPIRE. It may not be reliably winter hardy throughout USDA Zone 5 where it should be sited in a sheltered location and given winter protection.
Noteworthy Characteristics
Ilex × meserveae, commonly known as Meserve holly or blue holly, is an evergreen hybrid holly that typically grows to 6-8’ tall, but occasionally to as much as 15’ tall. In the 1950s, Kathleen K. Meserve of St. James, New York made crosses between I. aquifolium (English holly - winter hardy to Zone 7) and I. rugosa (Tsuru holly - winter hardy to Zone 3) for purposes of creating an English-style hybrid that would have sufficient hardiness to survive the harsh winters of the northeastern U.S. Her efforts resulted in the creation and introduction of a number of hybrids, known today as the Meserve hollies, but which are also often called blue hollies because most have the word blue in the trade name or cultivar name in reference to foliage color. Distinguishing features of these bushy evergreen hybrids are (a) average height to 6-7’ tall, (b) glossy blue green leaves with prominent spiny margins, (c) purple stems, (d) greenish-white flowers in small clusters in May, (e) showy bright red berries on female plants in fall, often persisting until spring, and (f) excellent winter hardiness to USDA Zone 5.
Subsequent to the original Meserve hybrids, some additional hybrids having slightly different parentage have been introduced into commerce as blue hollies.
Genus name comes from the Latin name Quercus ilex for holm oak in reference to the foliage similarities (holm oak and many of the shrubs in the genus Ilex have evergreen leaves).
The hybrid name meserveae honors Kathleen K. Meserve (1906-1999) who developed the original Meserve holly hybrids.
‘Heckenstar’, commonly marketed under the trade name of CASTLE WALL, is a male evergreen Meserve holly with a compact, upright, pyramidal form. It typically matures to 8-10' tall and to 3-4' wide. It is a dense shrub that features small, oval to elliptical, serrated, glossy deep green leaves (to 2” long). Greenish-white flowers in clusters of 2-5 appear in May and are generally inconspicuous. CASTLE WALL was discovered in 1998 in a selected breeding program in Barmstedt, Germany from a cross of the unpatented Ilex aquifolium ‘Pyramidalis' and Ilex x meserveae BLUE PRINCE. U.S. Plant Patent PP14,308 was issued on November 18, 2003.
Problems
Potential insect problems include holly leaf miner, spider mites, whitefly and scale. Potential disease problems include leaf spot, leaf rot, tar spot and powdery mildew. Plants are also susceptible to leaf drop, leaf scorch and chlorosis (yellowing of leaves in high pH soils).
Uses
Borders, screens, hedges, foundations. Glossy evergreen foliage (male and female plants) plus contrasting red berries (female plants) provide excellent winter interest.