Tuesday, November 24, 2009

Invasive Shrub Color

In fall, the local woods become a color-coded forest, making it easy to tell at a glance what species are growing where. Trying to take at least some advantage of this, I headed out in a car to survey where Asian photinia has invaded our nature preserves. The combination of its yellowish orange color and customary growth form aid in identification from the road.

Here's a new invasion getting going up on Mt. Lucas.

Once Photinia has lost its leaves, the honeysuckles are still green, revealing just how extensive is their invasion of the woods. That they hold their leaves long after native woody plants have dropped theirs suggests that the exotic honeysuckles evolved in a climate with a longer growing season.

Mountain Lakes Projects--Butternuts, Plant Rescue

Have a spicebush! As part of a planting project around Mountain Lakes House, Friends of Princeton Open Space board member Tim Patrick-Miller led a plant rescue on the old lower dam at Mountain Lakes. The dam will be enlarged this coming year, burying all existing vegetation. All told, we rescued five spicebush shrubs and four swamp rose.

In another project, initiated by Princeton resident Bill Sachs, we planted 20 butternut seeds outdoors, then covered them with metal screening to prevent pillaging by squirrels.

The butternut is a rare native tree threatened by an imported canker disease that is reducing their numbers even further. Bill, who edits the Nutshell, a newsletter for the Northern Nutgrowers Association, has been scouting out where these trees can still be found in Princeton. Until we get DNA analysis, we won't know whether the trees found are the native butternut, or a hybrid with an imported species.

Native shrubs fall color

Both these shrubs are native, but I've never seen them in the wild. That may have to do with their natural range being the southeast. They've been widely planted in the north, for obvious reasons. The first is oak-leaved hydrangia (Hydrangia quercifolia).

This dwarf fothergilla (Fothergilla gardenii) was planted at Mountain Lakes House, and has been left alone by the deer.

Salamanders at Herrontown Woods

While digging around the foundation of the historic Veblen House (soil and landscape timbers had been pushed up against the wood siding--not a great way to preserve wood), I came across some salamanders.

One played a game of peekaboo, crawling under a dandelion leaf after I let it go.

"Snakes with legs" is one way to describe how they move, but their soft skin and improbably tiny feet confer an air of vulnerability.

Friday, November 13, 2009

Red Berries in the Forest

There are lots of red berries in the woods right now. Consistent summer rains have made for a bumper crop. Here's some help in distinguishing between them all.

Asian photinia (Photinia villosa) is a robust exotic shrub that reaches twenty feet high and can be found singly or in dense stands. The leaves are "obovate", meaning they are often widest towards the tip. The berries are in terminal clusters.

Winterberry (Ilex vericillata) is a native shrub typically found in lowlands. At Mountain Lakes, its leaves are still showing a little green, and the berries are tight against the stem, rather than in terminal clusters.

Swamp rose (Rosa palustris) is another native, also found in lowlands. Its hips are larger than those of the exotic multiflora rose, and its thorns are not curved backwards like the fishhook-shaped thorns of multiflora rose. Also, the thorns of swamp rose are more dense towards the base--the opposite pattern found on multiflora.

I'm calling this Viburnum dilitatum, the linden Viburnum--an exotic shrub that is proving fairly invasive. It's leaves could be mistaken for the native Viburnum dentatum, but are wavier and less toothed along the edges.

Wednesday, November 11, 2009

Photinia Spreading in Princeton's Woodlands

Asian Photinia (Photinia villosa) is a shrub that land managers in the Princeton area are targeting for removal from natural areas. It was sold by Princeton nurseries many decades ago, and has begun invading the local woodlands. Why are we so worried about this shrub that turns a pretty golden color in the fall, with bright red berries?

There are many reasons. For one, the shrub appears not to be edible for wildlife, and 2) the shrub has shown a capacity to out-compete the native shrubs and forbs wildlife do use for food. The spreading monoculture of Photinia in the forest understory is rendering the landscape less and less hospitable for the native diversity we seek to nurture.

An additional reason for focusing on Photinia is that it has yet to spread across New Jersey. Action now in the Princeton area could prevent Photinia from becoming a statewide pest.

This is a typical sight under berry-producing Photinias: a dense clustering of seedlings that leaves little or no room for native species to survive.

Photinia is very easy to spot this time of year. Nearly all native species have already dropped their leaves, making the woods a color coded picture of various invasive species. Honeysuckle shrub leaves are still bright green, Photinia's are golden yellow.

Here's what the woods looks like after a very dense patch of Photinia has been cut and stacked. Not as pretty, to be sure, but it's the first step in restoring a more edible native landscape for wildlife that will also be pleasing to the eye.

Homeowners are encouraged to identify and remove Photinia. Though it may be appealing from the standpoint of its deer resistance, the spread of the berries threatens the ecological balance far beyond the boundaries of one's backyard.

Spicebush Swallowtail Caterpillar

A Friends of Princeton Open Space board member found this caterpillar on her front door one day in July, and just recently found out what it is. Though we have lots of the butterfly's favorite host plants--spicebush and sassafras--growing in Princeton woodlands, particularly since the browsing pressure of deer has been reduced, I have never seen one of these caterpillars. The one that showed up at Brownlee McKee's door might have something to do with a spicebush her landscaper planted just two weeks prior, and so it's hard to know if this particular caterpillar originated in Princeton, or was transported with the shrub from some distant nursery.

Below are her notes, and a link she found to a wonderful photo portrait of all the different shapes a spicebush swallowtail takes as it grows towards adulthood. Thanks to Brownlee for sending the photo and info.

07/16/09 Spicebush Swallowtail caterpillar on front door of house within a couple of weeks after setting a Spicebush 15 feet from the door. How the 'pillar got there, past 10 feet of boxwoods, over five feet of brick paving, and a foot or two up the door, is a mystery. It was a striking sight, with the sun bringing out its bright yellow against the dark green of the door. In this picture the pale background and some shadow dulls the bright yellow.

Here's a website with many photos and more info.

Japanese Maple--Very Pretty, Kinda Scary

At the old Veblen farmstead at Herrontown Woods, the delicate leaves of Japanese maple decorate the woods next to the old cottage that once served as the world famous mathematician's study.

Japanese maple in all its varieties is one of the most gorgeous trees around, but the way it can sprout copiously in people's gardens has always made me wonder what could happen if it got loose in the woods. That's what's happening at Herrontown Woods--the kinda scary aspect if one values native diversity in the natural areas people have worked so hard to preserve. Sure is pretty, but the wildlife may not be sitting pretty if they find it inedible.

Saturday, November 07, 2009

Butternuts and Bladdernuts

It's a pleasure to encounter a new kind of native tree for the first time--one rooted in this continent's deep history, a new-old friend. I first heard of butternuts (Juglans cinerea) as a rare relative of the walnut that was becoming even more rare due to an imported canker disease.

An opportunity to finally see one came after meeting Bill Sachs--Princeton resident and editor of the Northern Nut Growers Association newsletter, The Nutshell--who is beginning a quiet campaign to find and nurture various kinds of native nut-bearing trees in town.

He recently recruited me as an extra pair of eyes to search for any companions to a butternut he had found in a private woodlot near Carnegie Lake. Butternuts have distinctive bark, with lots of long, flat "ski runs" zigzagging down the trunk. Red oaks have this feature as well, but the vertical plates are not nearly so dense.

We soon found a second tree, with many nuts beneath it. The nuts look like oblong walnuts. Whether these trees are pure butternuts or are the result of hybridization with Japanese walnuts will have to await genetic analysis.

Later in the search, we came upon a lovely overlook of Lake Carnegie, with rock bluffs populated by uncommon species. This photo shows bladdernut, whose seeds (not really nuts) can be found inside the "bladders." This is the third population of this native shrub that I've found in Princeton.

The rock bluffs have an ancient quality to them, as if the rock has been buckling slowly over the eons from its own weight.

Though we didn't find any more butternuts, Bill also identified a persimmon tree by its bark--a female with a few fruits still clinging to the branches.

Sunday, November 01, 2009

Gingko biloba

This is a good time of year to spot Gingko trees (Gingko biloba), a commonly planted tree in Princeton. It is a "living fossil", meaning that the western world knew it only from fossil evidence before it was discovered growing in China. Its bright yellow foliage stands out now, with leaves clustered along lanky branches. The leaves grow off of "short shoots" that project from the branch (see second photo). Female gingkos are a mixed blessing, as they litter the ground with malodorous fruits.

One owner of a large female tree told me he used the odor to advantage, by dumping the fruits back in the woods where some teenagers had occasionally been getting together to drink.

The gingko in these photos is at Little Brook Elementary. It will be interesting to see how quickly it sheds its leaves. Some drop them all in a day.