Ilex crenata
Japanese holly
Common names: Box-leaved holly
At a glance
- Light
- Partial shade
- Hardiness
- Hardy down to −20 °C
- Pruning
- May–Jun
- Flowering
- May–Jun
- Spacing
- 40 cm, rows 40 cm
- Water need
- Medium
Photo: KENPEI · CC BY-SA 3.0 · Source
Description
Ilex crenata, known in German as Japanische Hülse, is an evergreen, densely branched shrub native to East Asia. It has small, glossy dark green leaves that resemble those of boxwood. Unlike the native European holly, which is also called Hülse, it has no spines, and its leaf margins are only finely scalloped. Depending on the cultivar, it grows 1 to 2 m tall and grows rather slowly. The small, whitish flowers appear in May and June and are rarely noticeable. Female plants produce tiny black fruits in autumn. In many gardens it serves as a substitute for boxwood, as the box tree caterpillar generally does not attack it. It can be pruned as a low bed edging, hedge, sphere, or cloud form, or grown in a container. It requires even moisture and a low-lime soil.
Care instructions
Plant Japanese holly in spring or autumn in a semi-shaded to sunny, wind-sheltered location with humus-rich, slightly acidic soil. For a low edging or hedge, space plants 25 to 40 cm apart. For individual standing spheres, allow 60 cm or more. Keep the soil evenly moist, especially in the first year and during hot summers, because its roots lie close to the surface. A leaf mulch layer helps. Waterlogging and drought cause brown, dropping leaves, while lime causes yellow leaves. Prune in May or June after the first flush of new growth, preferably on an overcast day. In winter, water on frost-free days when the soil is dry, and protect sunny spots with fleece.
The care notes were machine-translated from German.
Garden year
FloweringMay–Jun
Soil & site
Soil pH
Soil type
humus-rich, well-drained, loamy, lime-avoiding
Japanese holly grows best in humus-rich, fresh and free-draining soil that is acidic to slightly acidic. On chalky soils its leaves turn yellow; leaf compost or a spot in a container with ericaceous compost then helps. Its roots are shallow, so it dislikes compacted ground and waterlogging. A layer of leaf mulch keeps the soil evenly moist.
Feeding
Medium feeder
Months
Apr, Jun
Japanese holly grows slowly, but welcomes feeding if you prune it regularly. In April, when new growth starts, work ripe compost or horn shavings shallowly into the soil, and repeat this once in June. After that, do not feed any more, so that the shoots ripen before winter. In a container, also give organic liquid fertiliser in spring and early summer.
Pruning
Japanese holly tolerates pruning very well and can be trained into hedges, balls and cloud shapes. Do the main cut in May or June, as soon as the first growth has firmed up; if needed, a light second cut follows in August. Cut on overcast days, as in strong sun the cut edges of the leaves turn brown. Older plants that have gone bare can be cut back hard in February; they usually sprout again.
Overwintering
Japanese holly is hardy in Central Europe and keeps its leaves. More dangerous than frost is winter sun on frozen ground: the leaves then dry out and turn brown. Horticultural fleece gives shade, and on frost-free days you water thoroughly. Mulch young plants with leaves in their first winter. In a container, place the pot against a sheltered house wall and wrap pot and plant in fleece in hard frost.
Propagation
Methods
- Cuttings
- Layering
Propagate Japanese holly by cuttings, but this takes patience. From July to September, cut semi-ripe shoot tips 8 to 10 cm long, remove the lower leaves and insert them in sandy seed compost. Kept bright, warm and evenly moist, they often root only after several weeks. Layering is safer: in spring, lay a low shoot in a small hollow and cover it with soil; after about a year you can separate it. The species is dioecious, so seedlings turn out very varied. Propagate varieties only by cuttings or layering.
For your garden
Grow Japanese holly yourself
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