Sunday, February 24, 2008

English holly

Location, location, and location! The beautiful, glossy-leaved English hollies (Ilex aquifolium) that we so highly prize (and rarely see) here are regarded as invasive pests on the west coast. English holly is a rarity in Plainfield. The only examples I know that can be seen from the street are two plants at 1332 Prospect Avenue.

English hollies have never been very commonly planted in the northeastern United States because they are considered insufficiently cold-hardy. They used to be seen occasionally in nurseries in this area. Now I almost never see English hollies for sale at all. They have been pushed aside by crosses between English holly and other holly species. One of those hybrids, Nellie R. Stevens, is by far the most abundant tree-form holly at the nurseries. There are two attractive Nellie R. Stevens hollies in front of the First Unitarian Society on Park Avenue near Seventh Street.

Nellie R. Stevens is thought to be a hybrid of English (Ilex aquifolium) and Chinese (Ilex cornuta) hollies. The original was found in the garden of Nellie R. Stevens of Oxford, Maryland. Nellie R. Stevens' big advantage is that it grows fast. It has a distinctive, glossy, blue-green leaf that is quite attractive. Its red berries are tainted by orange, but it makes up for that weakness by producing berries even in the absence of a male plant to fertilize it. Such berries are sterile.(1) Nellie R. Stevens' real failing is that it is even less cold-hardy than English holly. In three of the last twenty years most of this area's Nellie R. Stevens hollies have had their foliage completely killed by winter cold and wind. Most of the leaves fell off, and those that hung on were brown. The plants weren't presentable again until July, if then. I have planted dozens of Nellie R. Stevens over time, but I gave up on them completely after seeing most of them defoliate two winters in a row a few years back. This is a problem that global warming will solve, and the forward-looking local nurseries promote Nellie R. Stevens tirelessly. Pictured below is minor leaf injury from the 2006-2007 winter, a relatively mild one.

Ilex cornuta, the other parent of Nellie R. Stevens, is rare in Plainfield (because of cold-hardiness concerns). I know of only one, at 1215 West Fifth Street.

I haven't observed the West Fifth Street holly after a hard winter. Its very handsome foliage, with most leaves single-spined, is pictured below.

'San Jose' holly is the most commonly available among the crosses between English and Perny hollies (Ilex x aquipernyi). The leaves are dark blue-green, glossy, thick, and stiff. It's hard to imagine a deer wanting to eat any of them. 'San Jose' hollies are resistant to winter as well as to deer. I have never seen winter injury on a 'San Jose' holly in the Plainfield area. The berries are large and pure red. 'San Jose' hollies grow slowly. Their branches tend to get droopy if the plants are shaded. There is a 'San Jose' holly (or other closely related Ilex x aquipernyi hybrid) at 950 Hillside Avenue.

Blue hollies (Ilex x meserveae) were bred on Long Island by Kathleen Meserve specifically to produce glossy-leaved hollies that could tolerate cold winters.(2) They perform that function quite well. But they want to be shrubs, not trees. You can buy them pruned to a tall and narrow shape, and I imagine that it's possible to maintain that form if you're diligent. These plants are most often seen sheared into mounds. Their beautiful blue-green leaves are softer and flatter than many holly leaves, and deer are more willing to eat them.(3)

What about the so-called red holly hybrids that have been available for the past several years? The foliage is glossy and beautiful, but I hear reports that they are subject to winter burn in our area unless planted in a sheltered spot.(4)

All of the hollies mentioned above have their advantages, but if I had to choose just one of them for this locale, it would be straight English holly. I have grown several varieties of English holly in my garden for more than 20 years and have never had problems with winter damage. No holly has more beautiful foliage than English holly. It is a shame that it has largely disappeared from the local market. The English holly variety 'Angustifolia' is pictured below.

(1) Unlike Komodo dragons (Birds Do It. Bees Do It. Dragons Don't Need To, Neil Shubin, New York Times, Feb 24, 2008, ), Nellie R. Stevens hollies are incapable of virgin birth. The berries that Nellie R. Stevens hollies produce in the absence of a male pollinator are seedless and incapable of generating new plants.

(2) Kathleen Meserve also bred 'China Girl' and 'China Boy', shrubby hollies that share some parentage with blue hollies. They are more tolerant of the heat than the blues are. To my eye, their foliage is much less attractive than blue holly foliage, and I wouldn't find much use for them in the Plainfield area. (To judge from the numbers of them that I see at local nurseries, my opinion is not widely shared.)
(3) Landscape Plants Rated by Deer Resistance, Pedro Perdomo. Peter Nitzsche, and David Drake. Rutgers Cooperative Research and Extension, New Jersey Agricultural Experiment Station, Rutgers, The State University of New Jersey 2004.
(4) 'Festive', 'Cardinal', 'Oak Leaf', 'Little Red', 'Robin', and others. Called red hollies for the reddish color of their new growth, they are widely available in local nurseries. I don't know of any that are visible from the street. Cory Storch is growing a 'Cardinal' in a sheltered spot in his garden; he reports that it is doing quite well. Claudia Heffner, a Master Gardener and landscape designer from Scotch Plains, reports that 'Oak Leaf' hollies planted in her garden have suffered significant leaf burn in winter. An 'Oak Leaf' that she planted in a sheltered spot in another garden is doing fine.

Copyright Gregory Palermo

1 comment:

Anonymous said...

Subject: Event in Caldwell

Let's Talk About Trees
Thursday, March 6, 2008 7:00 pm
Caldwell Borough Council Chambers, 1 Provost Square, Caldwell
Admission is Free

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Organized by the Caldwell Environmental Commission.