Time to pull the mustard

Garlic mustard (Alliaria petiolata), that is. This exotic wildflower, introduced to the U.S. from Europe in the late 1800s, is killing our woodlands.

From the New York Times, May 2, 2006:

Researchers have found that it disrupts a healthy relationship between hardwood tree seedlings and soil fungi, with results that can be disastrous for a forest.

Many plants make use of arbuscular mycorrhizal fungi, which form an elaborate network of filaments throughout the soil. These fungi are a diverse group, but they all have one thing in common: they help plants take up nutrients from the soil, getting carbon in return.

Garlic mustard is a member of the mustard family, "one of the very few families that do not need to associate with mycorrhizal fungi at all," Dr. Stinson said. These species produce chemicals that have antifungal properties. Native mustards have been around long enough, she suggested, that the mycorrhizal fungi have learned to live with them. But the fungi haven't had time to adapt to garlic mustard. "It basically is killing off the fungi," she said.

It bullies out our native spring ephemerals, it secretes a compound which destroys the soil fungi that is critical to the survival of our trees, and it fools a native butterfly to lay eggs on it that its the caterpillars can't eat. Here's a primer on the proper protocols for pulling it out. It's a prolific seeder, so bagging it is important.

The ways of Callery pear

Callery pear (Pyrus calleryana) planted along Rt 440 in Staten Island.

Callery pear (Pyrus calleryana) planted along Rt 440 in Staten Island.

Callery pear (Pyrus calleryana) volunteering along Rt 440 in Staten Island.

Callery pear (Pyrus calleryana) now found in Conference House Park. That was easy math.

Asian Longhorn Beetle infestation

The Asian Longhorn Beetle has found its way to a natural area on Staten Island. ALB was first discovered in the US in street trees in Greenpoint, Brooklyn. The insect is thought to have arrived here from woody packing materials from China. ALB has proved to be persistent and able to spread from infestations when eradication has not been completed.

Now it looks like half the trees on the island will need to be cut down and chipped (which is how USDA treats this infestation). It should be interesting to see what comes back - on the Brunswick shale dreg island that is Pralls. Let's just hope this is the first and last natural area where we find these beetles.

Update:
Video of ALB on Pralls Island from the Staten Island Advance.

Backyard Invasions

The curator holds an herbarium sheet. These are invaluable for determining historical floristic compositions of an area, among other things.

(For more about herbarium sheets and their botanical role - click on "store")
The article "New exhibit focuses on invasive plants," is about a new exhibit at the Carnegie Museum of Natural History, features images of invasive and endangered Pennsylvania plants. The display — both informative and elegant — is a combination of drawings, paintings, etchings, and giclées (digital prints).

Overall the article does a good job of framing the issues, with the exception of the author's final comment about cultivars that "are native plants" that "can satisfy a consumer's wants without harming the environment." This is not entirely true, but that discussion is a post in and of itself.

Educating the public about the ecological costs of invasives is important, as they continue to devastate our systems. Case in point, newly published research shows how a honeysuckle shrub (Lonicera mackii) used in gardens and landscapes harms forests by disturbing the understory layer, tree reproduction and mature tree productivity.

Hardwood stands from southwestern Ohio had noticeably lower species diversity and vegetation cover below the shrubs to detect growth changes 25 years prior to and 25 years following invasion. The growth rates of overstory trees was reduced significantly. The effect of this slowdown were first observed about 6 yrs after invasion with the greatest frequency of negative growth changes occurring 20 yrs after invasion.

The abstract - Hardwood forest invasion by a non-indigenous shrub (Amur honeysuckle) negatively affects overstory productivity (a pdf)
More on the invasiveness of shrub honeysuckles

Natives for Invasives

This is a great new publication - there are lots of natives I hadn't thought of using in a horticultural situation. I do have a suggestion for improvement, however. There should be some kind of warning regarding use of Celastrus americana where people need to make sure these plants are purchased from a trustworthy source and labelled properly. Their exotic breathren are very similar and so hard to differentiate - especially the M. rubra. It's for exactly that reason that I tend not to recommend them to the average native plant gardener. That said...
Native Alternatives to Invasive Plants is an indispensable guide for everyone who loves dazzling gardens and cares about the health of North America's natural landscapes. Invasive plants, the overwhelming majority of which are not regionally native, brazenly spread unchecked across residential landscapes, parks, preserves, roadsides, and other wild lands, supplanting native species and ultimately threatening the ancient biological communities in their path. In fact, most scientists now consider invasive species to be one of the top two threats to this planet's native plants and animals (the other is habitat loss). Invasive species cause major environmental damage amounting to almost $120 billion a year. Yet invasive plants are still commercially available, and a few of them remain wildly popular. Japanese barberry, for example, is one of the hottest-selling plants in the nursery trade, and Norway maple is one of the most widely planted trees in the country.

Sand Sedge Spreading at Shore

The Jersey shore - our beloved shore. After I got back from my Avalon trip, I remembered having read something about an invasive sedge at the shore. Sure enough - I found the culprit (in print, not in person). Asiatic sand sedge (Carex kobomugi)

• How to recognize Asiatic sand sedge
• Learn more about Asiatic sand sedge

Avalon's Gardens

I'm lucky enough to be able to spend Labor Day weekends down the shore in Avalon, NJ. (And, it is "down the shore", not "at the beach"). Between lying on the beach, under an umbrella and jaunts in the ocean, I, of course, walk the neighborhood and scout out plants. Here, I present "Avalon's Gardens: Dos & Don'ts".

A definite do! Switchgrass (Panicum virgatum) is a great choice for the full sun and well-drained soils that dominate the yards in Avalon. This is a grass that you'd find occurring on its own in such a site. (Ignore the exotic boxwood and juniper flanking it).
A definite don't! Japanese barberry (Berberis thunbergii) and purple loosestrife (Lythrum salicaria) are highly invasive! And, what's with the cedar chip fetish?
Yam-leaved clematis (Clematis terniflora). Looks great, smells nice, invasive. A don't. This photograph was taken in someone's front yard. You know where else I saw this plant? Along the trees of the Garden State Parkway, for miles and miles.
Ah no! Chinese silver grass (Miscanthus sinensis) - invasive! (And obnoxiously huge, no?)

To end on a positive note - a joe-pye weed(Eupatorium sp.). A definite do, and quite the looker. Its a great nectar plant for butterflies, and has interesting seedheads in winter.

NY Sues over Invasive Pests

Asian longhorned beetles (Anoplophora glabripennis)

The states of New York, California, Connecticut and Illinois are suing the U.S. Department of Agriculture (USDA) for failing to impose effective controls against destructive insects that enter the country in shipping pallets and other wooden packaging.

Invasive insect pests - - such as the Asian long-horned beetle (Anoplophora glabripennis), emerald ash borer (Agrilus planipennis), and pine shoot beetle (Tomicus piniperda) - enter the country in wooden pallets and other packaging made from raw wood. These pests have caused significant damage to trees in New York City, Long Island, Chicago and other communities. Thousands of trees have been destroyed in an effort to prevent the spread of these pests, which have few local predators or diseases to kill them. If these destructive insects spread from U.S. ports of entry into the nation's forests, they could further damage the timber, tree nursery, fruit orchard, maple syrup, and tourism industries.

Read more on the lawsuit

More information on the Asian long-horned beetle, emerald ash borer, and pine shoot beetle

Now showing in Alaska

When talking about purple loosestrife (Lythrum salicaria), the noxious "purple menace" invader from Europe, its distribution in the United States is always mentioned. "Found in the continental U.S." or "in 48 states". Make that 49 - now appearing in Alaska as well. There are no safe harbors.

• More on purple loosestrife's invasive ecology
• More on purple loosestrife in NYC.
• More on biological controls

I've been knotty

Just in time for the holidays!

The place to buy mugs, clocks, and other gear for your favorite invasive plant hater...is here What stone cold heart can resist a knotweed-hating teddy bear?

New Invasive Plant Field Guide

Invasive Plants Field Guide: An ecological perspective of plant invaders of forests & woodlands.

A source for information on key plant invaders in eastern forests. The guide examines 15 main species in four plant categories and presents extensive information about each. There is also a references section. Full color photos appear throughout.

The publication is put out by USDA (#NA-TP-05-04). It can be downloaded here as a pdf.

Will the real Aralia elata please stand up?

Japanese angelica tree (Aralia elata)??? Nice fall color, which I have never seen on (& reported doesn't exist for) the ubiquitous other Aralia.

Japanese angelica tree (Aralia elata)??? with infructescence

Devil's walking stick (Aralia spinosa)???

Welcome to the world of botanical taxonomy. For your entre, I thought we would go right for the jugular. Devil's walking stick (Aralia spinosa) is native to the U.S. Most literature cites its range as Delaware & south (e.g., Gleason & Cronquist). One (Mitchell & Tucker) says it's native to New York State. So I called our state botanist who assured me that G&C was right, it is not native to NY. In fact, field work has shown that there is no A. spinosa in the state at all. Everything we have been seeing is actually Aralia elata, an exotic invasive. There is a population of Aralia spinosa out on Long Island, but that was shown to have piggybacked in on nursery stock from North Carolina.

So when a colleague of mine called me to say he had found an interesting Aralia, I was excited. To compare, we began with the familiar.

We went to Highbridge Park in northern Manhattan. There was a small cluster of less than 10 shrubs in an opening in the forest canopy, not far off a trail. This is the Aralia shrub that I see all over NYC. It had dark green leaves held at almost a 90 degree angle to the main stem. We were calling this "spinosa" based on the leaves - veination (joined before margin) & finely toothed, no obvious pubescence. The fruit panicles no longer held berries & had already whithered, so we didn't take a sample.

Now, the fun part. Next we went to Fort Washington Park, a subset of Riverside Park in northern Manhattan (around 158 St.). There were maybe 5 shrubs scattered along a stretch between a trail & fencing for the Metro North train line (so not obviously colonial like above). These plants were new to me - I had never seen this species before. We were calling this "elata" based on the leaves - veination (run to margin), broadly toothed & obvious pubescence. Additionally, these leaves were lighter green & held at a more acute angle to the midstem.

So we sent the samples to Brooklyn Botanic Garden - I could barely get to sleep that night, I was so excited to hear back what the new-to-me plant was. Apparently they think they are both the same species...Aralia elata. They said what they really need is the point at which the inflorescence attaches to the main stem - that is the critical piece distinguishing one from the other. Oh. We didn't get that. But still, sometimes I think taxonomists are too by the book. Can't you just tell which is which? If I can ID species with just basal leaves, I expect a little more info when I provide such bounty.

And so the mystery continues..........
OK, OK, I know. Don't go by leaves. Flowers/fruits are more stable, & so the basis of taxonomic determinations. But c'mon - these have to be two different species. (And additionally, if you aren't supposed to look at leaves, then why the difference between Smilax herbacea & S. pulverulenta (NYS rare) - the former has no hair on it's leaves, the latter has hair. Be consistent, people!)

Invasive willow threatens wetlands, rare plants in East

Egads - another one.

From The Boston Globe

A European invader has been sneaking onto the New England coast, infiltrating and undermining the natives.

The large gray willow, a shrub or small tree that spreads rapidly and closely resembles our native pussy willow, has been flying under the radar for years, colonizing the edges of ponds and crowding out rare plants and animals throughout the eastern United States. It was just identified this spring.

Other countries that have been invaded by the species, Salix cinerea, also called the European gray willow, paint a grim picture. New Zealand considers it a major "pest plant". Australia calls it the worst of the invasive willows and warns it can cross-pollinate with other willows.

There is concern about the threat to coastal plain ponds that are host to a whole complex of rare insects, animals and plants, including the Plymouth gentian, rose coreopsis, hyssop hedge-nettle and slender marsh pink, as well as rare dragonflies and damselflies.

The European willow's presence is confirmed for Cape Cod and Rhode Island. It is expected to show up in coastal areas stretching from Maine to Long Island. The Harvard Herbaria in Cambridge, Mass., has a specimen collected in Old Orchard Beach, Maine, in 1967, so the willow has a lengthy head start on efforts to control it. (Yet ANOTHER reason why herbaria are so important!!)

The full article from The Boston Globe

More on Salix cinerea

Botanists battle aliens in Acadia park

The plant busters, an elite team of national park botanists, had come to the Great Meadow on a whirlwind mission to search and destroy some of the alien, invasive species that have put down stubborn roots in the park.

"The more you look, the more you see," Betsy Lyman of the Northeast Exotic Plant Management Team said while pointing out an undulating green sea of alder buckthorn saplings. "It's an endless task."
The scrubby alder buckthorn saplings immigrated from Europe sometime after the 1800s, she said.

They spread rapidly and may be detrimental to the local wildlife in part because their large purple berries are attractive to birds but don't provide nearly the amount of nutrition that Maine's native berries, like the winterberry, do.

"For birds, it's kind of like eating junk food," Linda Gregory, Acadia National Park botanist, said. "This is not great wildlife food."

Read the full article from the Bangor Daily News

Phrag in Iraq

With all of the bad news spewing forth from Iraq, I thought it might be time to post this. Phragmitis australis or "common reed" is one of the most invasive plant species in the northeast. Toiling diligently to destroy it, in this country restoration workers use mechanical & chemical means to squelch its vigor. Maybe we should take a page out of the Iraqi notebook. There, it is native & is used by Iraqis living in the northern marshes to build boats, housing, and temples. The temple in the photo below is said to be cool even at noon in the desert.







An article from NY Times in March on restoring the marshes of northern Iraq that were destroyed by Saddam Hussein.

More about Phragmites australis in the U.S.

Jewelweed Runs Amok in England

Jewelweed (Impatiens capensis), native here, invasive abroad.

Our ubiquitous jewelweed is an unwelcome visitor in England. Eric von Wettberg is studying the species genetic bottleneck in its adopted digs. Since a small number of individuals made the initial invasion, he is looking at how the plant has evolved its shade avoidance response (by which plants fit their growth patterns and phenology to maximize their success under a range of light conditions) to fit its new environs.

More on his work

An Alien Invader Spawns a Species

From the Christian Science Monitor:
The influence wrought by invasive species could fuel an "explosion" of ecological change "to levels beyond all expectation."

UN to Court over "Devil Tree"

A tribal community in Kenya is planning to take a United Nations agency to the International Court of Justice in The Hague for introducing a harmful tree (the mesquite - Prosopis juliflora) to the country. The action, thought to be a world first, is being brought by the Ilchamus people of the Rift Valley, again the Food & Agriculture Organization (FAO).

Read more

Invasive Norway Maples Threatens LI Forests

Exotic Norway maples invading a forest in Queens. Note the dense shade & lack of ground vegetation.

From the Long Island Botanical Society's newsletter, summer 2005 - summary of Wei Fang's research & article:

Norway maple (Acer platanoides)was first introduced to this country in 1760s & quickly gained popularity as an ornamental species. By the late 1990s, it was considered to the be the #1 planted street tree in the U.S. In recent years, Norway maple has expanded from its ornamental realm into sections of parks & nature preserves. Once there, it forms single species (monospecific) stands & inhibits groundcover establishment.

Wei Fang's three year study showed that not only is Norway maple expanding its reach within the forests of Long Island, but as the number of Norway maples increases, so too does the number of other exotics, such as Japanese honeysuckle (Lonicera japonica) & winged burning bush (Euonymus alatus). Furthermore, limits the availability of resources to other plants - its larger leaves exclude other vegetation from receiving sunlight & it changes soil chemistry resulting in higher nitrogen loss.

Here is the abstract.

Struggles with an Invader

Back to Nature & What a Mess - from today's New York Times

An excellent example human's unexpected consequences on the landscape. Here, Anne Raver's struggles to contain the invasive tree - black locust (Robinia pseudoacacia) on the family farm. Anne, I feel your pain. However, I wish she had discussed & compare the ecological roles of native early successional trees & exotic invasives - they are quite different. When the latter dominates an area, it is not succession, nor is it competition or evolution - it is an invasion. All our open space, even so called "pristine" landscapes, need to be nudged along. We are now in the sad position of having to manage lands just to enable processes that should occur normally on their own.

More about black locusts