Dependably hardy, at least as far north as southern New England, Japanese holly is also easy to grow in the mid-South.
Like American holly, the Japanese make a larger plant there.
In fact, it can become a small tree in that mild climate.
Ilex crenata and its varieties remain handsome throughout the most bitter New England winters.
They neither assume the dull appearance of conifers nor show the leaf-curl of kalmia, pieris, and rhododendrons.
Japanese Holly Simple Cultural Requirements
Japanese holly thrives in full sun or partial shade.
It should be planted in well-drained soil to which peat moss and well-rotted or dried manure have been added.
A permanent mulch of peat, pine needles, or similar material is a safer weed control than cultivation which may damage fibrous surface roots.
Spring feeding with cottonseed meal, dried manure, or complete acid fertilizer is desirable.
Height Variations Of Japanese Holly
Deep summer watering encourages vigorous growth.
Although 2 or 3 varieties of Japanese holly are well known, many gardeners do not realize that there are many kinds with greatly different shapes and subtly varied foliage.
The “original” or typical Ilex crenata exhibits a wide variation in height.
In New England, we seldom find it man-high.
In the South, it is commonly twice as high as a man.
As the shrub seldom gets very broad, it is better as an accent around a small house than fast-growing pyramidal arbor-vitae.
Small dark green leaves bear rounded, shallow teeth, as the name “crenata” implies.
The shiny black fruit is borne abundantly, but only by female plants.
Ilex Crenata Variations
As there are many forms of Ilex crenata, it is practical to mention only a few with especially distinctive branching habits and leaf patterns.
Ilex Crenata ‘Longfellow’
Ilex crenata ‘Longfellow’ (probably a synonym for Ilex crenata longifolia) reveals an upright shape similar to the above but remains compactly branched without trimming.
Leaves are about an inch long, very narrow, and among the most attractive of all Japanese hollies.
Ilex Crenata ‘Glass’
Ilex crenata ‘Glass’ is also upright, but if not pruned will be much more open than ‘Longfellow.’
Leaves of ‘Glass’ are only ⅓ the size of those of ‘Longfellow’ and are very closely spaced.
Ilex Crenata Totundifolia
Ilex crenata rotundifolia is one of the most robust and fastest-growing of all Japanese hollies.
I have planted it in the sunniest, windiest corner without any trace of winter damage.
Even when branches are split by heavy ice, they spring back and recover.
This rotundifolia (sometimes listed as latifolia) is compact but forms a broader, somewhat more spreading plant than the forms just described.
Large leaves are 1” inch long and a ½” inch wide contribute to its massive appearance.
Ilex Crenata Convexa
Ilex crenata convexa (bullata) is hardier than Ilex crenata.
This convex-leaved Japanese holly is very slow-growing.
The first plant introduced into this country nearly 50 years ago is still flourishing at the Arnold Arboretum.
Although it keeps spreading, its height is not much more than 6’ feet.
Ilex crenata convexa ‘Hetzi’ is somewhat faster growing than Ilex convexa.
It has a similar shape but the leaves are a bit larger.
‘Hetzi’ bears fruit abundantly when still young.
The plant originated near Lake Erie and is quite hardy.
Ilex Crenata Helleri
Ilex crenata helleri, which appeared as a “sport” in Rhode Island, is one of the older and better-known extremely dwarf Japanese hollies.
Small leaves are spaced closely.
As the plant is very slow-growing, it is suitable in a small rockery or by a step where even such a dwarf conifer as Taxus cuspidata nana would soon use up the available space.
Ilex Crenata ‘Kingsville’
Ilex crenata ‘Kingsville’ is similar to helleri, as is ‘Stokes,’ a patented variety that first appeared in Pennsylvania.
As Japanese hollies come to be more widely offered, they are sure to be used more freely in mixed borders and foundation plantings.
They are more easily kept within bounds and look better throughout the year than many over-planted conifers.