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February Cleanup at Greenbelt
By Don Recklies, Naturalist
Photos
Forest
Restoration #176, Saturday, February 19, 2011
What a difference a day
makes! Friday, partially sunny,
reportedly got up to 70! Unfortunately
our 176th Forest Restoration was on Saturday, the wind gusting and morning
temperature around freezing. It was
chilly standing in the lot at High Rock Park, so four of us shouldered our
weed hooks and weed wrenches and trekked toward Pump House Pond where
scattered clumps of Aralia elata, the alien
relative of our Devil’s Walking Stick, were waiting for us. The trail above Loosestrife Swamp was still
crusted with snow and ice, as was the part of the Yellow in the shade of the
Moravian Cemetery fence, and that made walking the slope difficult. Fortune took pity on us, however, and once
past the swamp we found the trail was mostly clear. Dropping into the valley further cut the
wind, and by the time we reached the pond we were relatively comfortable and
knew that we would warm up further once work began.
Close to the pond there were only
a small number of these aliens, and our intention was to remove them before
they became mature enough to flower and seed.
These plants are shallow-rooted, and when young can usually be pulled
by hand. They can quickly grow to 15'
to 17', however, with trunks that can be 4 inches across, and these larger
specimens require using tools to wrench them out or saw them down. Wrenching is the better choice since they
will easily re-grow from roots left behind when they are cut, and using a
weed-wrench to lever the whole plant out of the ground is easier on the hands
as well! They are somewhat brittle
trees, and in the winter can often just be broken off at ground level,
although, like trees incompletely wrenched they will sprout again from their
roots. We set to work, and in a little
less than 2 hours had all that we could see mounded in a brush pile a little
off the trail.
I should note here that I’m
careful to refer to the plant the Alien Devil’s Walking Stick. There is a very similar plant, Aralia spinosa, called the Devil’s Walking Stick, that is
native west and south of us, and for several years it was assumed that this
native had moved north with the increasingly warm summers and was now growing
in our woods. Botanists at the New
York Botanical Gardens took a closer look, and with the aid of DNA analysis
(so I’m told) determined that the Devil’s Walking Stick we see is an Asian
cousin of our native plant, and that none of the native species occurs on
Staten Island. The two plants,
however, are very difficult to distinguish from another by marks one can
observe in the field.
Once familiar with this spindly
shrub, it is easily recognized on the trail, leafed out only at branch tips
and usually armed with nasty, thin, sharp spines and marked with curious,
narrow, semi-circular scars that wrap almost all the way around the stem and
mark where the leaves were attached.
Just like people, plants differ from individual to individual, and these Aralia display a range of thorniness. Botanically speaking, perhaps that’s the
wrong term. As a matter of trivia,
some botanists distinguish between thorns, spines, and prickles. Should you get on a quiz show, thorns are
plant stems modified to come to a sharp point, spines are modified leaves,
and prickles are sharp outgrowths from the bark layer. Most scholarly sources and the US Forest
Service, which describes the plant as a potentially invasive alien already
invasive in Pennsylvania, use the term prickles. (Of course, if I’ve led you wrong about
this don’t blame me for losing half a million dollars. You should have made up your own
mind!) Whatever you choose to call
them, some of these plants are so unarmed that they can almost be pulled up
with bare hands, but most will require stout leather gloves. The young ones often seem more vicious than
more mature saplings, but much of this is due to previously
sharp...prickles?...being rubbed off and worn down on the older bark. One of the curious attributes of the plant
is that both the trunk and leaf stems bear prickles although you may have to
examine several leaves to find the prickles growing beneath the midribs of
the leaf stems.
In the winter the plants seem
most noticeable as straight, thorny (I’ve already done the prickle bit, I’m
going to be inconsistent from here on) sticks about 2 to 4 feet high. Usually there are taller ones about, but
it’s more difficult to notice the taller ones when they spear through the
branches of other shrubs. Close-up
though, their spiny appearance is extraordinary, and during the growing
season they are visually remarkable as well.
Unlike most of our other shrubs, after they have grown a season or two
they begin to leaf out mostly toward the end of their stick-like stems. The leaves are what we call doubly
compound, and are sometime triply compound. What appear to be individual leaves are
actually leaflets that grow from the stem of a much larger leaf, and
these stems in turn grow from a main stem attached to the branch of the
tree. This business of leaf stems branching
off a main leaf stem is what makes it doubly compound. All of this structure is a single leaf
growing from a single leaf bud. These
leaves can become very large, and it’s not uncommon to find them several feet
long. During their life the tree will
branch only a few times, still leafing out mostly toward the ends of their
branches. The overall appearance is
umbrella-like and, like an umbrella, they create a deep shade which retards
the growth of other under-story herbs and shrubs.
Other parts of the tree are
striking as well; in August they begin to produce large panicles - branching
flower clusters - of off-white blossoms which stand out in this mostly green
season in the woods, and by September those blossoms have become pyramids of
rings of black berries, or drupes which is what we call a fleshy fruit
surrounding a hard, single seed, which tempt the birds. That temptation must be very successful,
since Aralia elata is now springing up all
over the Greenbelt. Several years ago
this relative of the Devil’s Walking Stick was a welcome curiosity, something
novel in the woods, but recently we’ve reached a tipping point and we find it
growing almost everywhere. Even after
the birds have stripped the trees of the berries, their appearance is striking. Up close, the berry stems make a vivid
lavender-pink tracery against the green leaves, and from a distance they
produce misty, colored patches unlike what we usually see in the woods. You’ve surely noticed them before, but they
were so few and scattered that you may not have been able to get close enough
identify them. Well, there’s no
problem getting close now... From what
I’ve said, you might get the idea that the tree is pretty. Well it is, and that’s why it became a
problem. Because of its fast growth
and striking appearance it was widely employed as a favored landscaping
plant, usually called the Japanese Angelica Tree, and was no problem planted
solely in urban landscapes. Birds move
around, however, and with them the seeds moved into the forests. There a different problem crops up. In the forest they shade out and displace
native plants such as spicebush and viburnums that bloom and fruit at times
that are better suited to feed avian migrants. Aralia elata
would probably not be any problem if it was encountered only occasionally,
but where it gets a foothold it seems to become established in great numbers.
A legitimate and now rather
pertinent question is whether it is useful for us to try to remove these
trees. They are relatively easy to
uproot, but one must balance the harm that they do against the effort
required to remove them and the distinct possibility that there are now too
many to successfully remove. They are
now very, very common in certain areas of the Greenbelt, but seem to be
patchy or non-existent in other natural areas on the island. Some USDA county maps don’t even show Aralia
elata as extant in the south-west Long Island
area, but those maps are obviously not up to date. I recently contacted the Department of Parks
Natural Resources Group to solicit their opinion about whether or not we
should continue our efforts to remove this plant, and was told that because
of a new law regarding tree removal, we should cease our efforts. This was not really an answer about whether
attempting to remove Aralia elata was
worthwhile, but until the situation is clarified we will not uproot anymore
of these alien trees. In the meantime
I will try to find out more about this rumored law. If new legislation has been enacted, I hope
it clearly defines to what it applies.
In such matters legal and botanical definitions are sometimes at
variance and the application of law can be troublesome. In the meantime, our schedule will include Aralia
sites, but if clarification hasn’t been forthcoming we will concentrate
instead on removing twining woody vines at those places. If and when I have more information, I will
pass it along.
DfR 02-26-2011
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