River Birch -- Overused

August 1, 2020

One of the most overused ornamental trees is river birch (Betula nigra).  Do not presume that I mean it is unattractive.  The bark can be very enticing, especially the cultivar 'Cully' (aka 'Heritage') pictured above.  This special lighter pigmented deviant was discovered at a St. Louis residence in the late 1970's by Jacksonville IL nurseryman Earl Cully (d 2017) and he profited substantially from marketing it.  I am originally from central Illinois and did much botanizing there yet never got to meet Mr. Cully.  However, my friend and mentor Dr. Wesley Whiteside (d 2015), to whom my Rantings book is dedicated, was a good friend of the river birch king and laudatory of his plant knowledge.

 

Now allow me to explain why this species is overused--frequently a wrong choice.  Know that the problem is more often than not due to the planter and not the plant.

 

(1) As the name suggests, river birch is a riparian species found along water courses and lowlands primarily south of the Wisconsinan glacial boundary.  Few places where the native river birch is planted in the urban environment offer the amount of water the tree needs for the leaves not to turn yellow and drop in dry conditions which is what commonly happens in late summer and early autumn.  River birch is a water hog with an extensive network of shallow fibrous roots.  A large specimen can easily use 100 gallons daily.  Due to both the hoggishness and roots, it is challenging to underplant, especially with plants that are themselves water-loving, yet many try.  When you water the underplanted hostas, for example, one is prompting the river birch to develop more competing roots in that area to take advantage of the greater accommodation (i.e., water supply).  The tree will prevail.

 

(2) The species prefers acidic soil, yet most of the clayey dirt in subdivisions where one commonly sees this plant decoratively situated is circumneutral.  In a basic (higher pH) situation the leaves are prone to be chlorotic (yellow due to nutrient deficiency--likely in the soil but not available due to the pH).  The leaves produced in stressed conditions also will be smaller.

 

(3) River birch can be quite large.  This fast-growing tree (several feet annually) is also a lumber species.  I have seen wild specimens over 30-inches in diameter.  The Indiana state record is almost 4-feet in diameter and over 70-feet tall!  Moreover, as I have frequently ranted, woody plants are indeterminate growers--do not stop growing unless dormant until dead.  Most people ignore, do not know or do not care and place their specimens too close to buildings, passageways and utility lines.  I am aware of instances where once established the river birch growth rate frightened the homeowner and they opted to remove the plant--the promised "mature size" was obviously a lie.

 

(4) The bark of older specimens is not nearly as attractive.  I have heard ugly.  Yet another example of youthful deception--a chapter in my Rantings book.  Bark on older specimens is dark--somewhat like crumpled crepe paper covered with soot--hence the specific epithet nigra.  The species is sometimes called black birch.  Furthermore, there is considerable variation in the attractiveness of the exfoliating bark and it is common for the bark to be obscured by low branches--inadequately limbed up.

 

(5) Birch seedlings can be a common woody nuisance.  I get them regularly in wet areas such as rain gardens and my artificial bog even though the nearest specimen is more than a block away.

 

'Cully' is apparently more resistant to bronze birch borer which is so destructive of most birches.  Stressed plants are more susceptible to disease and infestation.  Since most river birch in urban locations are stressed, the resistance claim is less likely.  Because of the borer, do not consider planting the beautiful paper birch in central Indiana.

 

Interested in a small tree with outstanding peeling bark, consider paperbark maple, seven sons, Japanese stewartia, Persian ironwood or lacebark elm (esp variegata).  I wish there was a dwarf of the native sycamore.

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