Leaves of Three

Poison ivy has three leaflets, the center one has a longer stem.  Leaves have a central vein
with secondary veins branching off from it.  Young leaves are glossy, but older ones are variable
 and leaf margins are all over the place.

After a mild winter in the Mid-Atlantic, it's been a cool, damp spring.  This seems to have brought out a lot of growth in the understory.  Included in this lushness is plenty of poison ivy, Toxicodendron radicans, formerly, Rhus radicans.  As I have been doing some weeding I have been vigilant for ‘leaves of three’, the rhyme for identifying poison ivy.  But that is not the only plant out there that sports three leaflets. 

Following are some common plants that bare some resemblance to the dreaded poison ivy.  Probably the most common look alike in the Mid-Atlantic region is box elder, Acer negundo.  When I first encountered this tree I thought OMG it’s a  poison ivy tree!  This tree reseeds prolifically generating a myriad of seedlings with bright green leaves divided into three leaflets.  While superficially similar to poison ivy, on closer examination you can see that box elder has an opposite arrangement of leaves and branches, while those of poison ivy are alternate.

Box elder has three leaflets that appear very similar to
poison ivy, but branching is always opposite.  Leaf margins are variable

Here they are side-by-side.  Box elder seedling at top has opposite branching,
poison ivy in mid-frame is opposite.  The yellow flowers are green and gold,
  Chrysogonum virginianum.

A close second in my experience is Virginia creeper, Parthenocissus quinquefolia. This rambling and climbing vine has the same habit as poison ivy, but it usually have five leaflets rather than three.  The confusion comes because the younger shoots often sport leaves with three or sometimes four leaflets.  When I spot these I carefully trace the vine back a little ways to see if it also has leaves of five.  Some people have sensitivity to Virginia creeper, but the reaction is not as severe as the rash most people get from poison ivy. 

Virginia creeper is a vine with a similar habit as poison ivy. 
Most, but not all, leaves have 5 leaflets.

Another understory tree that has three leaflets is common hoptree or wafer ash, Ptelea trifoliata. This is not likely to be confused with poison ivy, although seedlings or growth from the base of the tree could cause some concern.  On the hoptree each leaflet does not have a distinct stem (petiolule), rather the leaf tapers sharply to the point of attachment.  While the leaflets of poison ivy are distinct with the central one considerably longer than the two lateral ones.  

Common hoptree grows well in shady locations not unlike poison ivy. 
Note how the leaflets lack distinct stems.

Aromatic sumac, Rhus aromatica, is less commonly encountered.  In the wild it is an upright shrub.  But in the landscape trade there is a shorter, spreading cultivar called ‘Grow Low’ that is becoming very popular.  When I’ve bumped into mine in the woodland edges I froze for a second until I noticed that the leaflets have different lobes and the leaflet stems (petiolules) are all the same length.  On poison ivy the middle leaflet has a longer stem than the other two.

The leaflets of aromatic sumac tend to have rounded lobes concentrated at the tips.

White avens, Geum canadense, has a number of leaf forms.  Some of its basal leaves can have three leaflets but they are not particularly glossy and are generally rough in texture.  Also this species grows in clumps, it is not viney.  

The younger leaves of white avens tend to have three leaflets.  To the lower left you
can see some of the more complex leaf forms.

Barren strawberry, Geum or Waldsteinia fragarioides and the non-native W. ternata, have leaves of three, but the leaf margins are more deeply toothed and the leaflet stems are all very short.

The glossy leaflets of barren strawberry appear to merge together looking
 more like lobes than separate leaflets.

  Mock strawberry, Potentilla  (or Duchesnia) indica, is another prolific ground cover with three leaflets.  It’s leaf margins are regularly toothed and it’s habit is different, spreading by stolons, not vining.  

The leaf surface of mock strawberry is much rougher in appearance than poison ivy.

Golden Alexanders, Zizia aurea, has leaflets that are twice divided, 3 sets of trifoliate leaflets (biternate).  The leaflets are ovate to lanceolate with finely toothed edges.  The long petioles may give the impression of young poison ivy stems.  

Leaflets of golden Alexanders can be seen in the circle at bottom right. 
Also present in this image is Virginia creeper and mock strawberry.

The native clematis, Virgin’s bower, Clematis virginiana, is a weak-stemmed vine with three part leaflets.  While you would want to routinely test the vine strength to distinguish it from poison ivy, an examination of the veins on the leaves would show the difference.  Virgin’s bower has a palmate pattern, with the major veins radiating from a single point; whereas poison ivy’s veins branch out along a central middle vein.  

The ribbed stems of virgin's bower are too weak to support itself
 and it needs something to climb on.

The list of trifoliate plants seems to go on and on.  After I thought I had this pretty well wrapped up I took another look and noticed the leaves of Jack-in-the-pulpit, Arisaema atrorubens, and that reminded me of the trilliums.  These can be recognized by their relatively large leaf size and regular arrangement of leaves.  Arisaema leaves are in a ‘T’ arrangement and those of trilliums are arranged in a regular triangle pattern (120 deg apart).  Can you think of any more poison ivy look-alikes to be on the watch for?

Under the Norway Maple - Part 2

As the growing season is slowly coming to a close I thought I would revisit the status of the native species I have be evaluating under my Norway Maple.  There have been some improvements and some failures and one plant that I thought I lost has returned in a different spot.  In general many of the plants continuing to grow, only slower and smaller due to competition from the mature Maple.

Maturing berries of Winterthur Viburnum start off
bright green, then turn pink, then finally dark blue.

First the good news.  After 4 years of growing with no berries, I finally got a good crop from my Winterthur Viburnum (Viburnum nudum 'Winterthur').  While it had been slogging along at the edge of the tree canopy, it produced no fruit until I brought in a native form last fall.  This year, with the cross pollination, mature berries were produced for the first time here.

Another plant the seems to be catching on is the Northern Sea Oats (Chasmantheum latifolium) that I moved in last year.  These overwintered and grew fairly well in the shade along the back fence.  I would like this grass to grow up and obscure the chain-link fence.  A new addition, that seems to be working out is the Bluestemmed Goldenrod (Solidago caesia).  The native habitat for this plant is in open woods, so at least this plant is used to the shade.



The Northern Sea Oats are doing well along the fence. 
The new Bluestemmed Goldenrod is in full bloom (late September)
and the Witchhazel is just getting started 



The Green and Gold (Chrysogonum virginianum) that I thought had faded away returned in a new spot and looked healthier this year than when it was first planted 4 years ago. 

I transplanted a lot of 2nd year American Bellflowers (Campanulastrum americanum, a biennial) along the back edge of the garden.  These did well though early and mid-summer until they died out after completing their bloom cycle.  The test will be whether new plants return from the seed. 

The biennial Allegheny Vine (Adlumia fungosa) did not come back with any new seedlings this year (unless they were lost in the spreading Virginia Creeper).  A new addition that I thought would work but did not do well was Canada anemone (Anemone canadensis); I will keep a eye out for this next spring.

Successes

Other plants that are expanding are:

The Rosinweed is standing tall while the Smooth Aster
and Showy Goldenrod have flopped forward toward the sun.

American Pennyroyal (Hedeoma pulegioides, an annual returning from seed), Smooth Aster (Symphyotrichum laeve), Heartleaf Aster (Symphyotrichum cordifolium), Rosinweed (Silphium integrifolium), Showy Goldenrod (Solidago speciosa), Virginia Creeper (Parthenocissus quinquefolia, now the dominant grond cover), and Wafer Ash (Ptelea trifoliata).

I should give a shout out to the Rosinweed.  While it does not have the prettiest flowers, it was in bloom all summer.  Then, I cut the spent blooms back to some new flower buds and got the second flush shown in the photo.  (Cutting back when no buds are present just leaves you with a leafy stem; I tried that last year.)

Plants holding their own:

  

Christmas Fern, Bellwort and Wild Bleeding Heart
have looked good all season.

 Male Fern (Dryopteris filix-mas), Christmas Fern (Polystichum acrostichoides), Rosey sedge (Carex rosea), Alumroot (Heuchera villosa),  Black Huckleberry (Gaylussacia baccata), Black-eyed Susan (Rudbeckia hirta), Lowbush Blueberry (Vaccinium angustifolium), Dutchman's Pipe (Aristolochia macrophylla), Largeflower bellwort (Uvularia grandiflora), Twinleaf (Jeffersonia diphylla), Wild Bleeding Heart (Dicentra eximia), Witchhazel (Hamamelis virginiana )

Fading or gone:

Barren Strawberry (Waldsteinia fragariodes) has disappeared and the Canada Mayflower (Maianthemum canadense) was down to only two sprigs in the spring before it disappeared.  Hairy Solomon’s Seal (Polygonatum pubescens) has been in this area for 4 years but it now seems to be in decline.  I put in a new one this fall and am hoping for its return.

Plants that should work, planned for next season:

Last year I planned to put in Labrador violet (Viola labradorica) and Maple-leaf viburnum (Viburnum acerifolium) but didn't.  I'll try to get those for next spring.  I will will also give the Canada Anemone another shot.  I also have some Large-leaf Aster (Eurybia macrophylla) that I should move over, seeing as it usually does well in dry shade.

In addition to using plants that are strong competitors that can get their share of moisture there are some maintenance practices that will help the understory plants survive under the Norway Maple (or other mature tree for that matter).  Limbing up and thinning the canopy to let in more sunlight helps a lot. Also, new plants should be irrigated deeply the first year to get them established, as well as under droughty conditions (mid-summer). I have a rain barrel with a special low pressure soaker hose to help with this.  Returning the leaf mulch to the understory area helps to build the soil.

Wild Urban Plants

Ever since hearing Peter DelTredici speak about Wild Urban Plants and his ideas on urban ecology last November at the 13th Annual Trees in the Urban Landscape Symposium at Tower Hill Botanic Garden, I have been wrestling with how that fits in with my approach to the use of native plants in urban and suburban environments. This talk explored the plants that are flourishing in the wild, unmanaged spaces in our cities, where they came from and why they are there. While 25-35% of these species are native to North America, many more are introduced species from other parts of the world. The difficulty for me was the apparent acceptance of many invasive and potentially invasive species as the new order of things. To help sort things out and not jump to conclusions, I read over a copy of his book, Wild Urban Plants of the Northeast.


I’m of two minds about this book. On one hand it is an excellent field guide for plants growing without cultivation in an urban setting. It is organized in the same way as Uva, Neal and DiTomaso’s Weeds of the Northeast, but with additional historical and cultural notes on how and why the plant has gotten itself established in the urban environment. These notes were very interesting to me in gaining a better understanding of why many of these introduced plants are so common. DelTredici includes over 200 species that are found growing in cities in the Northeast, from Detroit to Boston and Montreal to Washington, D.C. In the introductory sections this book points out the difficulty of doing strict botanical restoration on an area where the original conditions no longer exist and restoration of those conditions is unlikely, if not impossible. The plants described in this book are examples of ones that have proven to be adaptable to the built environment that is the modern city.

Where I began to have real differences with this book was its description of the ‘Brave New Ecology.’ Here it states that the cosmopolitan collection of plants (natives and introduced species) is the default vegetation for cities in the Northeast. While most would agree that having some vegetation is better than nothing (with some exceptions), I believe that we could be operating at a higher level of ecological function if there were more native species filling the urban niches, than introduced species. The major ecological function that natives support better than most introduced species is supplying nutrition to insect larvae, one of the most basic levels on the food web. I would refer you to Douglas Tallamy’s Bringing Nature Home for a fuller discussion of the role of native plants in the food web.

Also in this book DelTredici tends to treat the urban ecosystem as isolated from more rural, less disturbed ecosystems. If it were the case that the cosmopolitan plants were ill-adapted to life outside the city and did not spread beyond highly developed areas, I would have fewer issues with these conclusions. But the seed from many of the introduced species do not respect any borders, being spread by wind (black swallowwort) or birds (porcelainberry, buckthorns & barberries) into the wider environment.


Many of the introduced species in the ‘cosmopolitan collection’ got their foothold 200-300 years ago as new settlements and, later, cities were being built. These plants were imported along with the new settlers and were preselected for these new urban habitats being built. This made me think, what would happen in an urban site without the addition of exotic plants? If instead of the European mixed seed banks that were brought into the developing urban areas of the North American continent, there were only indigenous plants present to fill the urban niches. We may then see a greater array of regionally native plants in the urban environment. One reason this has not happened is that the native seed banks were not as large or as close to the urban environment as those of the cosmopolitan plants.


For nearly any habitat on earth there seems to be a plant or two that are able to grow there, as this book documents. In the case of the urban environment the ‘problem’ is that many introduced species were given first shot at these newly created lands, while otherwise appropriate native species were nowhere nearby. It would be interesting to see how some natives fared in the city when better matched to the actual growing conditions. Perhaps some more native species that grow on calcareous outcrops or cliffs would be found growing in sidewalk cracks. Looking at the plant community for calcareous outcrops in Massachusetts (found in west and central Massachusetts) there are a number of desirable plants, including red columbine, purple clematis and downey arrowwood.




A roadside planting of Seaside Goldenrod
and Appalachian Blazing Star
with some indigenous Milkweed

What I would like to see is a resource that looks for similarities between habitats in and around urban areas (the built environment) and natural areas that have similar chemical and physical attributes. In addition, there are many plant species that require disturbance to survive, in fact, many of these are on the threatened and endangered lists dues to a decline in ‘natural’ disturbance like fire and agriculture in the Northeast. Some of these may be candidates for native urban plants.

One example of a native plant that is expanding its range, included in his presentation but not cited in the book, is Seaside Goldenrod, Solidago sempervirens. This seaside species has been spreading inland along highways that have similar cultural (growing) conditions as in its native habitat, that is, sandy, salty soils with lots of wind and other disturbance.


Looking around the foundation and at cracks in the pavement around my house I have several native species flourishing. These include the understory tree, Wafer Ash (Ptelea trifoliata) and herbaceous species, like pink tickseed (Coreopsis rosea), swamp verbena (Verbena hastata), a variety of asters and the ever-spreading bearded-beggarticks (Bidens aristosa).

These have been speading in cracks in my driveway
for over 5 years.

Introduced plants are not evil, they are just growing and reproducing as they were made to do. But, as the dominant sentient species, we have choices of what to use in our landscapes. Selecting plants that appropriate to the location and support the local ecology is more responsible than just picking plants for use as ornamentation. With a little work, and trial-and-error, we can find more native species to enrich our urban and suburban environments.

If you would like to hear more about native plants and urban ecology check you the Ecological Landscaping Association conference this week (March 3rd) in Springfield, MA. There will be a panel discussion titled "Native, Introduced, Invasive and Endangered Plants in the Landscape:Untangling the Roots of the Problem", the panel features three experts including Peter Del Tredici, Bill Cullina, a native plant expert and author and Jono Neiger a leading figure in permaculture.

It's not Poison Ivy

As I was surveying which native species were growing successfully under my Norway Maple (for a future blog post), I came across many seedlings with ‘leaves of three.’ I thought, #Golly#, Poison Ivy! On closer examination, I realized that these were growing as individual plants, not a vine and the leaf shape, with its entire, unlobed margins, just wasn’t quite right for poison ivy. After checking some field guides and looking for similar plants growing in the area, I found out that these were seedlings of Wafer Ash, Ptelea trifoliata. The parent plant was growing behind the garage in an area I rarely paid any attention to.

Wafer Ash, also known as Hop Tree or Stinking Ash, is native to the Southeastern and Midwestern States, its native range does not extend up to Massachusetts, but it is listed as hardy to zone 5A.  I’m not sure how this tree got into my yard.  It’s not commonly used in the landscape trade and with a name like ‘Stinking Ash’ it’s not likely to be popular.  This name refers to the musky odor of its bark and leaves when crushed.  In this case, the name is a bit deceiving; I find that, while not pleasant, it does not smell as bad as something like wild Black Cherry.
Wafer Ash grows as a large shrub or small understory tree with irregular branching, usually growing to about 20 feet in height. The seedlings put down a tap root that can make them difficult to pull up.  It is native to dry rocky uplands and is very tolerant of shade. These two features make it suitable for growing under a Norway Maple, with its dense network of thirsty roots and dense shade canopy. Wafer Ash prefers neutral soils and is listed as deer highly resistant and tolerant of salt and ‘mine spoils’. The only conditions it does not tolerate are soil compaction and flooding.

This tree blooms in early to mid-June in the Boston area with terminal clusters of yellow-green, sweet smelling flowers. (Some sources list flower scent as unpleasant, but I found it quite nice and detectable several yards away.) The tree serves as a larval host for Eastern Tiger Swallowtail and Giant Swallowtail butterflies and is generally attractive to birds and pollinating insects. For more photos and information check out this link to the Wildflower Center.

The name ‘Hop Tree’ refers to its use in earlier times as a hop substitute in the brewing of beer. The dried seed pods (samara) can be decorative. My experience under the Maple and elsewhere in my yard is that these seeds high viability and offspring can appear just about anywhere. I don’t know if their spread is a result of being blown around naturally or from being caught up and thrown around by the lawn mower.

In my experience, the Wafer Ash is an excellent North American native understory tree with high wildlife value for dry, shady conditions. While it not commonly available in the landscape trade, there are a few commercial sources. Lacking that, I’ve got a bunch growing in my backyard. (You can reach me through the Adams Garden fan page on Facebook.)