Sunday, March 23, 2008

Cornelian cherry dogwood

Spring arrives in Plainfield before the vernal equinox. Its coming is announced by the bloom of the mysterious yellow-flowered trees lining both sides of the Park Avenue entrance to Cedarbrook Park. Blooming with the earliest crocuses, these trees announce that winter is over and brook no argument. The best time to view them is in the morning, when the sunlight comes streaming over the rooftops to illuminate the yellow flowers and make them glow. It's a sight that enlivens many a morning commute. Surely these trees are one of the best features of Cedarbrook Park, which was designed by the Olmsted firm.

I have heard the trees identified as witch hazel (They're not.) Or spice bush. (Not that either.) Nonagenarian Barbara Sandford tells me that, when her children were very young, she taught them that the Cedarbrook Park trees were called Cornus mas (a.k.a. Cornelian cherry dogwood. Barbara has known that the trees were dogwoods for quite a while.) After I planted some Cornus mas in my own garden, I noticed that the Cedarbrook Park trees invariably flowered two weeks before my trees or anyone else's Cornelian cherry dogwoods. So my bet is that the Cedarbrook Park trees are not Cornus mas, but rather Cornus officinalis, a very rare bird and a close Japanese cousin to the European Cornus mas. Cornus officinalis is supposed to flower earlier than Cornus mas and berry later. Whereas Cornus mas berries in July, Cornus officinalis is supposed to berry in September. I have never gotten myself well enough organized to check for berries in September, though. This season I'll do it without fail.

A Cornus mas at 1785 Sleepy Hollow Lane was just beginning to bloom when I photographed it today, more than two weeks after the Cedarbrook Park trees opened their buds.

Both Cornus mas and Cornus officinalis berries look like bright red olives. They also resemble the fruits of Japanese Aucuba, which is in berry now.

Do your Aucubas make berries like these? If not, perhaps your plants are sex-starved.

This female Aucuba, lost in the depths of a shrub border in my garden, is right next to a male. Clearly, she is not lacking for pollen, as evidenced by this generous berry crop. Other female Aucubas not far away produce many fewer berries. With Aucubas, proximity helps pollination. Familiarity breeds berries. Perhaps the insects that pollinate Aucubas are not as wide-ranging as the honey bees that pollinate many of our flowers.

Unfortunately the only male Aucubas I have ever found for sale have leaves that are variegated. Having searched for years for plain green males without success, I gave up, bought variegated males, and hid them in out-of-the-way corners. Fortunately, Aucubas are among the most shade-tolerant plants, capable of growing almost in the dark, so the variegated males are quite easy to hide.(1)

The best-looking Aucubas I know in Plainfield flank the entrance at 972 Kensington Avenue.

Aucubas are at the northern limit of their hardiness in central New Jersey and can be killed back to their roots by an unusually harsh winter. I have seen most of Plainfield's Aucubas killed to the ground once in the last twenty years. They looked as though they had been struck by lightning and burnt to a crisp, reduced to small black cinders. Nothing looks quite so dead as a winter-injured Aucuba.

More on hollies

I wrote in my February 24 posting on hollies that I had heard complaints that the red holly hybrids, including 'Oak Leaf', were susceptible to winter injury in the Plainfield area. Peter Simone writes that there are two 'Oak Leaf' hollies just behind the low privet hedge and flanking the walk at his house at 1414 Watchung Avenue. Peter says that his hollies have not been injured by cold weather, but that deer have eaten a fair amount of one of them. Red hollies have softer leaves than many hollies, and when we think "soft", deer must think "tender".

There is an English holly at 937 Woodland Avenue. A smaller American holly is growing into it, making comparison between the two species easy.

There is an attractive blue holly hedge on Pine Street, alongside 1402 Watchung Avenue

(1) Perhaps my preference for plain green Aucubas is idiosyncratic. To be fair, I have to admit that variegated forms of Aucuba were introduced into cultivation in the United States three quarters of a century before green forms, so someone thought they were attractive (Michael A. Dirr, Manual of Woody Landscape Plants. Stipes Publishing Company 1998, p. 115.) In some places, variegated Aucubas are so much more popular than green varieties that plain green ones are hard to find. Around Lakes Como and Maggiore in northern Italy, where they grow 15 feet tall, Aucubas are used for hedging as commonly as we use privets here. I looked for and failed to find a plain green Aucuba hedge there several years ago. The lacustrine Italians want them variegated.

Copyright Gregory Palermo

Sunday, March 9, 2008

Southern magnolia

Do you have doubts about climate change? New Jersey gardeners don't. As warming winters have threatened to make New Jersey into a southern state, its gardeners have started planting southern magnolias (Magnolia grandiflora) everywhere. In the 1980s, the only southern magnolias I knew of in Plainfield were at the former Memorial Funeral Home on East Seventh Street. Now East Seventh Street has seven southern magnolias within a length of just 300 feet. 1330 East Seventh Street at the corner of Coolidge Street is southern magnolia central.

Many varieties of southern magnolia are cold-hardy in New Jersey. The best known is 'Edith Bogue', named for Miss Edith Bogue of Montclair, NJ, in whose garden it first attracted notice. My experience with 'Edith Bogue' is that it is a rapidly growing, beautiful plant that has stayed green in winters that have browned my Nellie R. Stevens hollies and blackened my aucubas.

Some southern magnolia varieties that can be purchased at area nurseries aren't as cold-hardy. A particularly beautiful and tempting one is 'Little Gem'. It is a small tree with smaller leaves than those of most southern magnolias. Unfortunately, even rather mild winters can cause serious leaf burn. An example at 828 Arlington Avenue is pictured below after the winter of 2006-2007, not a very hard winter.

The tree is in much better condition this winter, which has been very mild so far, but this 'Little Gem' would probably be happier in Virginia.

Some of the varieties of southern magnolia that thrive in New Jersey have leaves with brownish, felt-like undersides.(1) A very handsome example is at 911 Woodland Avenue.

The Woodland Avenue tree shows a feature that is common in southern magnolias, the tendency to grow in a Christmas tree shape. European gardeners often take advantage of that tendency by treating southern magnolias as topiary specimens. Most southern magnolias that I have seen in European gardens have been formally pruned to form perfect cones. An exotic look that is well suited to an exotic plant; in Europe, southern magnolias are imports. I rarely see formally pruned southern magnolias in the United States, where the species is native. That sort of formal pruning is extremely high-maintenance gardening, by the way. It's very different from pruning a yew into a cone. Yews, with tiny leaves, can be shaped with shears. One can't prune southern magnolias with shears because their leaves are too large; the leaf fragments would be grotesque. Each stem must be cut individually with hand clippers.

Southern magnolias are capable of reaching great size in our climate. The grandest southern magnolia I have seen in the vicinity is at 221 East Westfield Avenue in Roselle Park. Twenty-five years ago, before the lower branches were removed, the house behind the tree was essentially invisible.

Magnolias are primitive trees. How primitive? Magnolias evolved more than 50 million years ago, before pollinators like bees and butterflies existed. Beetles are their pollinators.(2) The huge, white, lemon-scented blooms of southern magnolias might be the epitome of romance, but their intended audience is beetles, not you.
A close relative of southern magnolia, but even more fragrant, is sweetbay magnolia (Magnolia virginiana). I have some sweetbay magnolias in my garden, but I would be grateful to hear of any examples of this species that can be seen from the street.

(1) There is apparently some correlation between brown leaf undersides and cold-hardiness (Manual of Woody Landscape Plants, Michael Dirr. Stipes Publishing Company 1998, p. 598). That correlation doesn't work for 'Little Gem', however.

(2) Magnolias, J.M. Gardiner. Globe Pequot Press 1989, p. 14.

Copyright Gregory Palermo