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?

Preping the Garden

Last year's garden did not do so well.  On reflection there are a number of reasons, some of which are in my control.  Others, not so much.  To do well all plants need sunlight, nutrients and water.  And in my location, protection from pests.  In my mind I was providing all those, but in practice I was coming up short.

Here's the garden half-way through: last year's growth raked out, garden mowed low,
3 beds weeded with scuffle-hoe and rake.  Note the log pile just beyond fence,
all that remains of the big box elder, Acer negundo.

I have been adding compost, shredded leaves and a little organic fertilizer in the past. Last spring I sent samples for a soil test and learned that levels of most nutrients were too high: phosphorus, potassium, calcium and magnesium.  On the positive side, there was an increase in the organic content and cation exchange capacity (a measure of fertility). So this year I will only add an organic nitrogen fertilizer to the soil.  Of the organic choices that had minimal phosphorus and potassium I considered soybean meal and feather meal, both with about 7% nitrogen.  I opted for the soybean meal because I could by it from the feed store for about 25 cents a pound.  One warning with the soybean meal that I read was that it could inhibit the germination of small seeds.  So I'm not using that in the beds where I am planting lettuce, collards, chard or arugula.  I'm hoping that the beans, peas, spinach and others will be OK.  I got all the fertilizer down now (mid-April) and that should give it some time to be digested by the soil biota and have food ready for the bulk or the planting in mid-May.

As far as sunlight goes, I thought that I had good exposure.  That may have been the case 5 years ago, but the trees have been growing taller and eventually cutting a couple of hours of direct sun from the garden area.  While I hate to remove trees, there was a big box elder just south of the garden that appeared to be causing most of the trouble.  Since box elders are pretty common here, it was only with a little difficulty to say good-bye to that tree.

We usually have good rain here and I have a soaker hose to put in place for supplemental water.  So for moisture, I should be in good shape.

The last problem is the critters.  Every time I think I have a solution, they seem to adapt, or another problem crops up.  The double fencing seems to keep the deer at bay and the buried chicken wire slows the ground hog down; however I think it can still climb over the chicken wire when it really wants to.  Last year many seedlings were getting eaten and I'm not sure who to blame.  This year I have a motion activated trail camera to use so I can get a clue as to what is getting into the garden.  I am also expecting that the thicker layers of wood chip mulch will make it more obvious where any burrowing is taking place.

Other garden preparations:

I cut back the long tips of the wild blackberries growing on the outer fence. 
This improves fruit quality and gives more space to move around.

I've allowed wild blackberries to grow along the outer fence of the garden.  This re-enforces that area against deer.  I've read that by pruning the side branches to 4-8 leaf buds the fruit quality is improved.  I've been doing that for a couple of years now and it seems to be true.  The 'managed' wild blackberries have larger, sweeter fruits than the unmanaged plants nearby.

Rather than cutting to the ground I left 1-2' of the hollow
Monarda stems as potential bee nesting habitat.

Another plant growing along the fence line is wild bergamot, Monarda fistulosa.  These grow up about 4' and are very attractive to bees in early to mid-summer.  The hollow stems can provide nesting sites for small bees, like mason and leaf-cutter bees.  Since these bees build their nests in summer and develop there through the fall and winter, these stems need to be left intact for over a year.  When I did the garden clean-up I cut most of these stems to leave 1-2' intact.  These old stems will disappear into the new growth by the end of spring.  I just need to remember to leave them alone for the next year. 

As a result of a lot of tree work done here this spring, I have a large supply of wood chips.  This year was therefore the year to replenish the garden paths with fresh chips.  Many folks don't like to use fresh chips in the garden because they take up nitrogen from the soil as they decompose.  Since I want to suppress growth on the paths and garden perimeter, these fresh chips are just the thing to use.  (This loss of nitrogen from the soil only occurs where the mulch touches the soil and does not significantly affect the root zone unless the wood mulch is dug into the soil.)

The gardens all ready for plants:  freshly weeded, fertilized and mulched. 
I ran out of mulch for the last two beds...we'll call this an experiment. 
The remaining greenery are mostly native perennials like
beebalm and coneflowers to attract pollinators.

One new thing I am trying this year is to put down a wheat straw mulch over the bare soil.  This should help with moisture retention and reduce the number of weeds, or at least those from new seeds being blown into the garden.  I am expecting that wheat straw is much lower in weed seeds than is regular hay.

Now it's (past) time to plant those peas!!!

Finding a Mate for My Plants

Berries of Winterberry Holly persist into well into winter
 when they provide late season food for birds.

Shortly after we moved into to our new place I identified a nice looking Winterberry Holly (Ilex verticillata) growing near the front door.  It was mid fall and I didn't see any berries on the shrub.  This meant that either it was a male plant or that there were no compatible males within 100 feet to provide pollen.  The bright red berries of Winterberry are its main ornamental and ecological feature. 

Female flowers have a large central ovary surrounded by undeveloped
stamen-like structures (lacking anthers).  This plant was blooming in early June.

I had to wait until the following June to get a good look at the flowers.  After careful examination it turned out that this plant was in fact a female.  The solution was to find a suitable mate, that is one with a similar bloom time.  I found a male cultivar at a nearby nursery called ‘Jim Dandy’.  I sat him next to the established female for a few days while I located a nearby spot to plant him.  

Male flowers have well developed stamen and a very small ovary-like center.
The male plant seemed to attract smaller sized insects.

By September I noticed a few of red berries on the plant.  Success!  I hope to see more berries next year as there will be a much longer time for pollination to occur. 

These red berries were formed by mid-August.  

One of my goals in designing a landscape is its habitat value.  That is, what does the landscape gives back to wildlife in the form of food and shelter.  So when I select plants I look for ones that produce flowers, fruits and/or seeds that wildlife can use.  When selecting plants from a commercial nursery many of them are cultivars, which are genetically identical.  This becomes an issue in the habitat garden if the plants are single sexed (dioecious).  It is also a problem for plants that have both male and female flowers on the same plant (monoecious) or have perfect flowers (both male and female parts in the same flower) if the plants are not self fertile. 

All this plant fertility can have a down side.  In a formal garden production of viable fruits and seeds may lead to increased weeding and spreading of plants out of their designed boundaries.  Also, some consider that the mess that falling fruits create outweighs providing food for birds and other wildlife.  Personally I think of the landscape as a dynamic thing that changes over time.  In the designed landscape plants need to be kept under some degree of control, but I really enjoy seeing native species spreading to new areas where they are happier than in my initial design.

Here are the flowers of a female persimmon.  They have large ovary structures.
Male flowers are narrow at the base.

My experience with the Winterberry Holly has heightened my awareness of dioecious plants.  I want to generate as much natural food for wildlife as possible.  Also I would like to grow some ‘wild’ fruits and berries.  Persimmons (Diospyros virginiana) are dioecious.  My established persimmon is a female, but I have not seen any fruit on it.  I have brought in four more new wild-type plants, at least one of these should be male.  I don’t know of any named male cultivars of persimmon; however there is one called ‘Meader’ that is self-fertile. 

In general female plants need at least one pollen source (male) close enough that pollen can be transferred.  This transfer can be by wind (grasses and many trees) or by insects (vectors) most flowering plants.  For native hollies, like Winterberry, a male should be located with in 50 ft for effective pollination, though pollination over greater distances (100-200 ft) may be possible. 

Female Box Elders are covered with seed pods (samara) in the fall.
I noticed some squirrels eating them right off the tree.

Some other dioecious plants that I have are Box Elders (Acer negundo), Junipers, Tupelos (Nyssa sylvatica), Yews and Goatsbeard (Aruncus diocus). 

Some plants with perfect flowers are not self-fertile.  This may not be convenient for a habitat gardener with limited space for lots of plants. However, it works out on the larger scale to provide the greater genetic diversity adaptation to change and continuation of the species.  I have posted a number of times about the difficulty of getting Viburnums to bear fruit when only a single cultivar was planted.

There are some practical situations where limiting plant fertility and reproduction is called for.  In urban landscapes Ginkgos are very successful street trees.  The fruits, however, are loaded with butyric acid and smell of dog poo when stepped on.  For this reason most cultivars in the trade are males.  In my last post about Jerusalem Artichokes I noted that these are not self-fertile.  By only using only a single cultivar one limits the risk that this somewhat aggressive native will spread by seed. 

Another issue for some in urban and suburban landscapes is pollen allergies.  In many cases these are due to the (over) use of male cultivars.  Males don’t produce messy fruits, but they still send out their pollen.  This results in a type of air pollution that effects sensitive individuals.  While searching for information about dioecious plants I came across an excellent resource book by Thomas Ogren titled Allergy-Free Gardening.  This book contains a lengthy list of dioecous plants and the sex of individual cultivars.  There is also an allergy rating for a wide variety plants including monoecious plants and those with perfect flowers.  I did not realize that many maples, such as Red and Silver Maples, came as separate male and female plants.  Since I am more interested in facilitating plant fertility for enhancing habitat value I see using this book differently than the author intended.  But, if I had a client with particular allergy problems this book would be an excellent resource for plant selection to design a low-allergen garden.