Sunday, May 4, 2008

A Tale of Two Trees

The two trees that were planted on my street in March leafed out over the last three weeks, and emerged as beautiful young Zelkova trees, most likely Japanese Zelkova, (Zelkova serrata) as these are a species listed on the NYC Department of Parks and Recreation list of approved trees for street tree planting. The majority of the existing trees on the block are Callery Pear (Pyrus calleryana), but there already is a mixture of a few other species that the two new Zelkovas are joining, including Ginko, European Hornbeam, Green Ash, and a few older Zelkovas.

Although they were planted on the same street, on the same day, these two trees have had very different experiences. The tree on the southern side of the street has had a much rougher go of it. A branch was torn off of the south side tree in early April, leaving a jagged wound. Coming home from work one day, I saw the damage done, and was afraid that this wound would provide an entry for insects and fungus to attack my new neighbor, stunt its growth, and possibly kill it. Luckily, another neighbor also realized the danger to the young tree, as the torn branch was pruned within a week.

To add insult to injury, the tree on the south side of the street remains shaded by neighboring buildings much more of the day than the tree on the north side of the street. This may not seem like such a big deal to us who can walk to the grocery store to get our food, but the Zelkova is stuck waiting for the sun to bring food to it, so building shadows can really get in the way of a good meal. In fact, the south side tree leafed out a few weeks later and continues to lag behind the north side tree in foliage growth. There undoubtedly were other factors effecting the slower growth rate of the south side tree (the wound, perhaps differential treatment at the nursery or during planting), but the southern exposure that the north side tree experienced certainly gave it a leaf up. Further down the street, the Callery Pear trees on the south side and at the corners (where they were able to get more sunlight) also flowered sooner and more this spring. Most people do not realize just how much of an impact building shadows have not only on what can or cannot grow, but also on the size, shape, and speed of growth of whatever is planted there.

North Side Zelkova

South Side Zelkova