During the last few months we have discussed hollies that are grown for their showy berries. This month we are examining hollies that are grown for their structural importance as evergreen hedges and specimens.
One of the most important features of your garden, particularly in winter, is the framework, the pattern that you observe from your kitchen window. This permanent, often evergreen structure, could be made of a variety of different plants, but some of the best for a hedge, between three to five feet in height, are the evergreen small leaved hollies.
Hedges are obviously not needed if you have an entirely naturalistic garden, but most gardens in the Philadelphia area have some formality, especially near to the house. Unlike in English gardens where the perimeter hedge, and often other hedges, divide the garden into smaller rooms, American gardens, especially front gardens, have for over a century often been kept open to the neighbors. Here the evergreens are most often found next to the foundation. For many plants it is too hot and dry there in the summer; situated under the eaves of the house.
How can you, as a gardener, get more from smaller hollies used away from the foundation? If you wander around the Landscape Arboretum for inspiration you will see that the Formal Gardens are divided up into garden “rooms.” This design dates back to the origins of the garden in the 1920s and 30s. Each area has a different feel or theme to it. The garden was designed in an axial arrangement with the previous dormitory building that burnt down, to be replaced by the present brick Dixon Hall. Hedges provide both protection and enclosure in the garden
|Ilex glabra "Shamrock" informal hedge in the snowy Formal Native Plant Garden here at the Landscape Arboretum. (In the background is the Bell Tower that used to call the girls of the Pennsylvania School of Horticulture for Women for a break of milk and cookies.)
The plant that is along the top of the rock wall, and around the Formal Native Plant Garden, is Ilex glabra “Shamrock.” This plant is native all along the East Coast, and is found in moist acid soil in the wild, but is also drought tolerant. Try to replicate these conditions in your gardens and Ilex glabra will do well for you. It can be pruned to the desired height, and does need some regenerative pruning every few years. It can also take some shade, but grows better in more sun. The foliage is a lustrous green and there are insignificant black berries on female plants, hence the common name of Inkberry.
This plant is hardy to Zone 4-5, but at the colder end of the range, like many broad leaved evergreens, may suffer some winter foliage damage. The cultivar Ilex glabra "Densa" is a PHS Gold Medal Winner from 1994 cited for its urban tolerance in a variety of conditions, its resistance to pests and diseases, and its ease of transplanting.
The other widely used small leaved holly with which Inkberry gets confused, is the Japanese Holly, Ilex crenata. The leaves of the Japanese Holly are often shorter and more concave than Inkberry, with a more toothed margin at the tip. Japanese Holly also gets confused with Boxwood. The quickest identification method is to look at the leaf arrangement on the stem. Boxwood has opposite leaves whereas the Japanese Holly has alternate leaves.
This holly does best in Zones 5-7 and does not appreciate being too cold or too hot. There are so many cultivars that are available, too many to name. Japanese Holly was introduced to America in 1898 by Charles Sargent at the Arnold Arboretum. Japanese Holly can be left to grow as a natural or semi-natural hedge or trimmed quite severely to be very formal. Best growing conditions are the typical moist, well drained soil, but there is tolerance of sun or some shade, and urban conditions.
The final group of hollies that we will discuss are the large group of hollies that are grouped together under the Ilex x meserveae name. These are the Meserve Hybrid hollies that were bred by Mrs. F. Leighton Meserve in New York State by crossing various other holly species.
As you can imagine, these are cold hardy and actually do very well in the Philadelphia area. These can be planted as specimens and not pruned, or planted as an informal hedge. Like other hollies they have the benefit of being able to take some shade. I use them in my own garden as a hedge along a woodland path.
One of the great benefits to using the Meserve hollies is that they really do not require much care. The leaves are also very attractive, being small, dark greeny blue, and very shiny. Like Ilex crenata there are many hybrids. Some of the most commonly available are “Blue Princess” — with nice small dark red fruit; “Blue Prince” would be a male pollinator. “China Girl” and its pair “China Boy” have more green foliage and are more heat tolerant. The yellow fruited “Golden Girl” is for those that want something different.
In this trilogy of holly articles we have seen a great variety of plants available for different landscape uses. This is the tip of the iceberg, and there are many more available. Keep your eyes open you will see them used in many gardens.
If you have any questions please feel free to email me at email@example.com.
Jenny Rose Carey
Ambler Arboretum of Temple University