Plant of the Month

POM

Russets for Autumn

The bright autumn accents of brilliant reds or blinding yellows seem to provide the official celebratory close to the growing season for most gardeners.  I must admit, as much as I enjoy the bright colors of autumn, there is something about a glowing orange, mixed with some russets that speaks more to me of the season – especially as these leaves fall earthwards and carpet the ground!  These autumn colors are easily found in one of our native trees, botanically known as Taxodium.


A member of the Cupressaceae or Cypress Family, Taxodium was once a far more cosmopolitan genus, but vanished from Europe around 2.5 million years ago. Today, the 2 species easily grown in NJ Gardens – Taxodium distichum and Taxodium ascendens – are found along the SE regions of North America.  Taxodium was originally lumped into the Cupressus genus by Linnaeus, but it was the French botanist Louis Claude Marie Richard (1754-1821), who correctly reclassified the genus.  Taxodium is derived from the Latin Taxus for the plant commonly called Yew and the Greek Eidos, meaning ‘similar to’.  Indeed, the individual leaves of Taxodium do bear a resemblance to that of Yew. 

Taxodium distichum or Bald Cypress is the larger of the two afore mentioned species; in time, it can easily reach heights close to 150’ with a spread of 60’!  The species epithet of distichum means two ranked and describes the two rows of light green, ½” long by 1/16” wide leaves that appear along the deciduous branchlets – to the casual observer, one might mistake the leaves and the deciduous branchlets for a compound leaf.  A majestic tree, it appears naturally from Delaware to Texas and typically inhabits moist or flooded regions that are subject to annual accumulations of nutrient laden silt.  Although well-adapted to areas that can seasonally encounter over 9 feet of water, Bald Cypress will grow perfectly well in average, well-drained soils!  Interestingly, it is the moisture content of the soil that determines whether the root system produces colonies of curiously appearing growths called ‘knees’ (as pictured below). 

POM

The knees will slowly grow to heights nearing 4’ and only appear in wet soils.  With some imagination, the knees can resemble small Prairie Dogs dancing on their hind legs!  Originally they were considered to be phneumatophores or root appendages that permit the exchange of gasses.  Research has shown that the knees do not conduct the transfer of Oxygen and Carbon Dioxide and the current theory is they grow in marshy soils to provide stability to the tree.  Bald Cypress is also economically valuable for its decay resistant timber and was used extensively for greenhouse construction during the 18th and 19th centuries.  The central portion of old growth tree is called the heartwood.  In Taxodium, a naturally occurring preservative called cypresserve accumulates in the heartwood, rendering it economically valuable.  It requires decades for this material to accumulate, which is why timber acquired from vigorous growing, younger trees is not decay resistant.      


Taxodium ascendens or Pond Cypress appears only along the coastal region from North Carolina to Louisiana.  Named and described in 1833 by the French botanist Adolphe-Théodore Brongniart (1801-1876), this plant is often described as a variety of Taxodium distichum.   Currently, it is considered as sufficiently unique to maintain species status.  It is a much smaller version to its cousin, only growing to 60’ tall and 20’ wide with a pronouncedly vertical habit.  The 3-4” long foliage appears as overlapping scales, not individual leaflets and it stands vertically along the branches, most likely providing the species epithet, although the upright habit may also be the inspiration for the species name.  It too produces knees in wet sites, although they are much smaller in size.  Pond Cypress inhabits regions without nutrient rich silt deposits and is a better choice for gardens with nutrient poor soil.  The cultivar ‘Nutans’ provides a more narrow habit with decumbent or hanging foliage, while Debonair® (pictured above in fall color) displays a uniformly columnar habit with upright, ferny foliage!
Taxodium remains a highly underused landscape plant and provides so much for the garden whether large or small, dry or moist.  If you relish russet orange fall color and colonies of dancing Prairie Dogs, this is certainly a plant to consider!