Plant of the Month

 

A Wintertime ‘Spice’ for the Garden

 

 

Plant of the Month Archive

As autumn slowly transitions into winter, so do our colorful plants of interest transition from deciduous to evergreen as their structure and form grows ever more apparent with every dropping leaf.  Clearly, the larger evergreen shrubs and trees are the most noticeable, but there are numerous perennials with attractive winter foliage.  One beautiful addition to woodland gardens are the Gingers, botanically named Asarum, which feature a number of species that retain their glossy foliage throughout winters chill.
Asarum is a member of the Aristolochiaceae or Birthwort Family.  There are upwards of 85 species within the family, although the current thought is to divide the family into 5 distinct genera.  They are native to regions throughout North America, Europe and Asia.  The common name of Ginger originated from the similarity of the smell and taste of the rhizome – a horizontally growing stem at or near the soil surface – to that of culinary ginger.  However, recent evidence reveals that it is not fit for consumption, as it contains compounds that cause kidney failure, as well as the highly carcinogenic Aristolochic Acid.  The family bears the name Birthwort due to the resemblance of some of the plants to a pregnant woman and the ancient medicinal concept known as the Doctrine of Signatures.  The Swiss physician Philippus Aureolus Theophrastus Bombastus von Hohenheim (1493-1541) described how a plant that resembled a human organ or condition, such as pregnancy, would cure any problems related to its human semblance.  As such, plants in this family were incorrectly thought to ease childbirth. 

Carl Linnaeus (1707-1778) penned the genus name of Asarum in 1753.   The name stems from the Greek Āsa, which means altar or sanctuary.  Āsaron is the plural form and was the name cited by the Greek physician and botanist Pedanius Dioscorides (40-90 AD) for European Ginger (pictured below right) in his five-volumeAsarum masterpiece Materia Medica.  The volumes detailed herbal medicine and proved to be the ‘go-to’ resource for the next 1,500 years!  The genus name most likely stems from the brown, urn or alter-like flowers common to the genus.  The flowers lack petals and are composed of three sepals or modified leaves that lie hidden beneath the foliage and close to the ground.  Collectively called a calyx, the outside of each sepal is covered by tiny hairs with the upper third reflexed back, allowing the anthers and the stigma to be visible.  The flowers are a deep, reddish brown in color and appear in late May and June.  Gingers are typically self-pollinated, although mycotrophic flies also visit and pollinate the flowers.  Mycotrophic plants are flowering plants that require pollinators, yet typically lack chlorophyll and derive their sugars from soil borne mycorrhiza.  An example are Indian Pipes or Monotropa uniflora that frequently appear in Eastern North American woodlands.

Linnaeus formally described European Ginger in 1753, appropriately naming it Asarum europaeum, with the species epithet meaning Europe.  European Ginger is native to Central and Southern Europe, where it grows in light shade in humus rich, well-drained soils.  Plants are very adaptable to pH and can thrive in calcareous Asarumas well as acidic soils.  Plants slowly spread to 15-18+” in diameter, providing a very attractive groundcover for intimate areas.  The dark green, heart or kidney shaped foliage is 2-3” wide and grows to a reserved height of 4-6”.  Plants are hardy from zones 4-7 and remain evergreen except in the harshest of winters.    


Another, more recently discovered evergreen species is Asarum splendens (pictured at left).  Originally, it was named Heterotropa splendens in 1982 by the Japanese botanist Fumio Maekawa (1908-1984).  Heterotropa comes from the Greek Heterus, meaning different and Trepo or Trope for turning, describing the different positions of the stamens.  Ching Yung Cheng (1918- ) and C.S. Yang (1933- ) properly named it asAsarum Asarum splendens in 1988.  The species epithet is from the Latin Splendo meaning glistening or shining and references the attractive silver mottling that adorns the foliage.  Native to thickets, grasslands and moist mountain slopes of southern and central China, i

t features larger, more elongated foliage than its European cousin, resembling an arrowhead more than a heart.  The Arnold Arboretum first introduced the plant into the United States in 1978, shortly after its discovery.  The foliage was found to be so attractive when it was initially displayed that divisions of the plant were stolen several times by coveting plant enthusiasts!    Plants are hardy from zone 7 (6)-8 and require mostly shaded locations with soils that do not become excessively dry.  In fact, the species is far more intolerant of drought than European Ginger, with the leaves collapsing onto the ground until rain returns!  Again hidden by the foliage, the dark reddish brownAsarum flowers are much larger than its European cousin, reaching upwards of 1” in diameter for those who wish to search below the foliage.  ‘Laughing Ghost’ (pictured above at right) is a selection that features ghostly white markings that, with a touch of imagination, resembles the imprint from a pair of puckered lips!

Yet another very worthwhile ginger for the Gardens is Asarum canadense, or Canadian Ginger (pictured at right).  Native throughout much of Eastern North America, my experience has found this plant to be a far more aggressive than its European and Asian cousins, vigorously spreading throughout large shaded areas of the Garden.  Although it is deciduous and vanishes for the winter, it remains a very effective textural plant throughout the summer with its course, 6” diameter foliage providing a wonderful contrast to plants with more  finely dissected leaves such as the Ostrich Fern (Matteuccia struthiopteris) pictured below left or Celandine Poppies (Stylophorum diphyllum).  The flowers display the typical dark, maroon-brown coloration Asarumand appear in late May and June along the rhizome, hidden amongst the foliage

Gingers are effective when used along the edge of paths and walkways, where the interesting foliage and flowers can be easily viewed or in drifts around shade loving shrubs.  Asarum splendens is also effective when interspersed among shade-loving perennials as it brightens and illuminates the garden, just as its species name suggests.  Still very underused, consider these evergreen gems as you look to enhance the ‘bones’ of your Garden for this and for many winters to come!