Squirrels eating the Norway Maple

I’ve had a love/hate relationship with the squirrels. While they are amusing to watch, they cause the most damage to the ‘cultivated’ parts of my landscape of any single creature in my backyard. They are constantly digging around new plants; they’ve dug up my single little huckleberry several times. I’ve been lucky in that they have not bothered my tulip or crocus bulbs, much.

Black Huckleberry in mid-April, has been dug up 2-3 times over 2 years.

On the positive side, I noted 3-4 years ago that I had fewer Norway maple seedlings to pull out of the lawn. Then that fall I saw the gray squirrels munching on the seeds, both in the lawn and in the rain gutters.  I understand that these seeds are not the first choice for the squirrels, but they are plentiful and easy to come by.

Squirrel dining on Norway Maple flowers.

Then a couple of weeks ago I saw a squirrel eating the flowers off the Norway maple. This was a new one on me, but anything that reduces the seed production gets a gold star in my book. I did a little checking on the web and found an interesting post by Albert Burchsted,  Apparently gray squirrels prefer the green flowers of the Norway maple over the reddish flowers of the Silver and Red Maples. The squirrels also prune the branch tips from several maple species, including the Norway, to get a drink of the rising sap. This explains the number of broken branch tips scattered on the lawn.


One other ‘destructive’ activity attributed to the squirrels is the snipping off of tulip flowers. While I have not actually seen the squirrels doing this, rabbits and/or birds may also share the blame, they seem to be likely candidates. The tulip flowers are neatly cut off at the base, leaving a mostly intact bloom to wither away nearby. While I have not been able to find my original source, I was told a while back that the animal doing this was after the condensation that collects inside the flower cup and not the flower itself. This creates a compelling image of a squirrel drinking from a tulip ‘cup’, but I would really like to see some proof.

Who did this, and why????

I would appreciate hearing from anyone who has caught an animal, squirrel or otherwise, in the act of tulip vandalism.

Under the Norway Maple

One of the most common trees in the residential setting is the Norway Maple, Acer platanoides. It was first introduced into the United State in 1756 by John Bartram. It is well adapted to the climate in the Northeast and grows well under a wide range of growing conditions, making it a preferred tree in urban and suburban landscapes. It’s tolerance of for almost any environmental condition, ability to grow in the shade, prolific seed production and overuse in the landscape has led to this becoming a dangerously invasive species in the Northeastern US.

Working in residential landscapes I often encounter the difficulty of working around this species. Its dense shade and greedy roots that suck moisture out of soil make it difficult to underplant. While many consider the Norway Maple as allelopathic (producing compounds that retard the growth of other plants), there are studies that indicate that this is not the case. (One study found no experimentally measurable allelopathic effects from Norway Maple.)  I think the problems encountered under a Norway maple are mainly due to the shade it casts and the dense network of roots that scavenge moisture and nutrients from the soil.

Norway Maple stump 6 years after a native species
restoration at Mount Auburn Cemetery

This photo shows the best method for dealing with a Norway Maple. Despite my disdain for this tree, I have not taken that step on my own property, yet. Since there is not another tree in the area to provide shade around the house for the hot afternoon sun I am hesitant to open up the canopy that much. Instead I have been exploring which native plants will grow under its canopy.

To get some ideas, I tried to learn about what grows the natural forest community along with Norway Maple in its native range (Europe and Asia). I thought I could find native equivalents to those European species. This tree is naturally found in mesic deciduous forests and mature riparian communities. While I did not find a definitive description of the other plants in this community (I’m sure that information is out there) I did get some clues from a site on the Plant Formations in the Central European BioProvince.  One shocking conclusion jumped out.

Many of the perennials and shrubs that grow in forests along with the Norway Maple are also invasive, or have tendencies toward invasiveness, in North American forests. These include goutweed (Aegopodium podagraria), fig buttercup (Ficaria verna), Tartan honeysuckle (Lonicera tartarica also L. xylosteum), yellow archangel (Lamium galeobdolon), and lily-of the valley (Convallaria majalis).  So I would be hesitant to recommend any new non-native species with the possibility of making a bad situation worse. However there were some others that are better behaved such as sweet woodruff (Galium odoratum), European ginger (Asarum europaeum), Siberian squill (Scilla sibrica), Tartan dogwood (Cornus alba) and fumewort (Corydalis solida) and some really neat plants like common hazel, Corylus avellana (from which comes ‘Harry Lauder’s Walking Stick’ ). 

In my own testing, I have been selecting native plant species that are tolerant of dry shade. So far I have found a number of natives that survive but do not flourish. It seems to be a general trend that all plants grow smaller and slower in that environment. However, there are a few that are more than holding there own. My plant list is as follows:


 

Smooth Aster and Showy Goldenrod,
both about 1/2 size of those
in other parts of the garden

Spreading:

American Bellflower (Campanulastrum americanum), American Pennyroyal (Hedeoma pulegioides), Smooth Aster (Symphyotrichum laeve), Heartleaf Aster (Symphyotrichum cordifolium), Virginia Creeper (Parthenocissus quinquefolia), Wafer Ash (Ptelea trifoliata) , Wild Bleeding Heart (Dicentra eximia), Witchhazel (Hamamelis virginiana ).

Holding their own:

Male Fern, still green after a couple of frosts.



Male Fern (Dryopteris filix-mas), Christmas Fern (Polystichum acrostichoides), Rosey sedge (Carex rosea), Alumroot (Heuchera villosa), Barren Strawberry (Waldsteinia fragariodes), Hairy solomon’s seal (Polygonatum pubescens), Largeflower bellwort (Uvularia grandiflora), Rosinweed (Silphium integrifolium), Showy Goldenrod (Solidago speciosa), Twinleaf (Jeffersonia diphylla), and Possumhaw Viburnum (Viburnum nudum).  This particular Viburnum was selected to improve pollination of the 'Winterthur' Viburnums nearby.

Promising, but still early:

Allegheny vine (Adlumia fungosa), Black Huckleberry (Gaylussacia baccata), Black-eyed Susan (Rudbeckia hirta), Inland Sea Oats (Chasmanthium latifolium), Lowbush Blueberry (Vaccinium angustifolia), and Pennsylvania sedge (Carex pensylvanica).

Failures, faded away or died outright:

Canada Mayflower (Maianthemum canadense), Fetterbush (Leucothoe fontanesiana), Foamflower (Tiarella cordifolia), Green and Gold (Chrysogonum virginianum), and Squirrel Corn (Dicentra canadensis). (When I moved the Leucothoe to a different shady location, without the root competition, it perked up after a couple of weeks.)

Plants that should work, planned for next season:

Labrador violet (Viola labradorica) and Maple-leaf viburnum (Viburnum acerifolium),

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. Limbing up and thinning the canopy to let in more sunlight has helped a lot. Also, new plants should be irrigated deeply to get them established as well as under droughty conditions (mid-summer). Returning leaf mulch to the understory area helps to build the soil.



I’d like to hear what other natives have worked for you under Norway Maples, or ones that have failed desperately.

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.)