Wednesday, October 28, 2015

Symphoricarpos orbiculatus (coralberry)

Symphoricarpos orbiculatus 2000-3453-A

Despite being ubiquitous across Kentucky (and all of eastern North America) Coralberry (Symphoricarpos orbiculatus Moench) is a species which, paradoxically, goes unnoticed by many people.  Perhaps it is due to being one of the smallest woody plants in our flora, with similarly diminutive leaves and tiny greenish-white flowers.  Other plants tend to comingle with coralberry, further obscuring its miniature components and creating something of a botanical chimaera in the forest.  It is a curious species for many reasons, but also a plant in the ‘indestructible’ category for landscaping purposes.
coralberry, entrance to Arboretum Woods, here co-mingling with Elymus spp., Sambucus, and others.

Coralberry is the type species for the ~20 taxa genus Symphoricarpos Duhamel.  The name comes from Greek, symphorein – bear together, and karpŏs – fruit; an allusion to the berries which are borne in clusters along each stem.  This species fruit are clearly its strongest advertisement, for in addition to them yielding the botanical name they also account for the various common names including coralberry, Indian currant, buckberry, and waxberry.  Furthermore, it is the fuchsia-purple fruit which appeal to us as landscapers as a result of being persistent through the winter months.   This is apparently due to the presence of saponin in the berries, a mildly toxic natural detergent.  Wildlife consider coralberry a culinary last resort throughout the winter, ultimately consuming fruit only if all other food sources deplete.

Though fruit remains primarily an ornamental attribute, coralberry should not be overlooked when it comes to supporting wildlife.  Coralberry is a member of the honeysuckle family (Caprifoliaceae) and its flowers are visited by bees, wasps, and flies, while foliage serves as a food source for caterpillars of several moth species.  Coralberry is low mounding shrub from 2-4’ whose spread is typically accomplished clonally when arching branches touch the soil and adventitiously root.  As a result, these small thickets serve as good cover and protection for a variety of small animals.
A large coralberry thicket surrounding a memorial bench in the Bluegrass region (Walk Across Kentucky)

A partially shaded woodland would be an ideal spot to see (and cultivate) coralberry.  However, it is a species adaptable to various extremes including deep shade to full sun, and wet to dry soils.  It can do just fine as a small woody backbone for shade gardens, meadows, and rainwater gardens where it will slowly spread itself.  Deer are known to browse coralberry, and in our experience it responds well (with vigor) with simulated browsing including hard-pruning, mowing, and burning.  
Shawnee Hills region (Walk Across Kentucky) growing in wet moderate-shade at the edge of pin oak grove

For those who have paid close attention to the progression of The Arboretum Woods, you might have noticed coralberry increasing in abundance.  We suspect this may be due in part to the elimination of Amur honeysuckle (Lonicera maackii), another member of the Caprifoliaceae whose niche is being replaced.  Certain native plants struggle to establish by seed through the carpet of the exotic-invasive wintercreeper (Eounymus fortunei), yet the ability of coralberry to clonally spread by stem-rooting have allowed it to bypass this impediment.  We are glad to see it on the rise.

Monday, October 12, 2015

Appalachian Magnolia Bed

There are many parallels between natural ecosystems and ‘garden’ ecosystems (those shaped by the hand of nature vs. the hand of man).   One such parallel is the unwavering reality of change in living systems – plants (among other life forms) grow, battle, and die.  For gardeners it may be easy to overlook the beauty of that concept in favor of frustration when prized plants get too big, become aggressive, or perish. 

For several years now we have been both the drivers and passengers of an evolving garden called ‘Magnolia Bed’ in the Appalachian region.  While the Magnolias planted within seem insignificant now, the long term goal is for this area to be a thick forest of bigleaf magnolia (M. macrophylla).    This post is intended to track to the garden as it changes over time, and thus far it has been an interesting study of species dynamics.

Above left: a severely overgrown patch of (predominately) black locust, devil's walking stick, sweetgum, and brambles.  Above right: The Native Plant Volunteer Team charging into the thorn forest.
After a month of clearing, the woody debris was fully removed and converted to turf for the following (2012) season.

All of the woody debris had been piled-up and covered with mulch on the far side of the bed.  Bigleaf magnolia seedlings were planted throughout the bed and protected from rabbits using plastic pots.  In an effort to smother the turfgrass, newspaper and cardboard were laid down before a heavy layer of mulch. 
The newspaper/mulch combo was very effective at killing turfgrass.  Winter weeds were hand-pulled prior to planting. 
Spring 2014 plantings included dwarf blazingstar (Liatris microcephala), Rockcastle aster (Eurybia saxicastelli), silky wild-rye (Elymus villosus), gray goldenrod (Solidago nemoralis), purple coneflower (Echinacea purpurea), streambank mock-orange (Philadelphus hirsutus), wild hydrangea (Hydrangea arborescens), and sweet pepperbush (Clethra acuminata).  The ironweed (Vernonia gigantea) and large mass of common milkweed (Asclepias syriaca) pictured above were holdovers from the previous tangle of woodies that reemerged after nearly 2 years buried.
To reduce weed competition during the first season following planted, spring oats (an annual cover crop) seed was broadcast into the mulch at the time of planting.  In late summer the oats had turned golden-brown (above).

A favorable spring and early summer led to a wonderfully thick garden in 2015.  Common milkweed (above background) continued to expand its range via underground runners. 
 Purple coneflower blossomed exceedingly well.
 Looking east into the Knobs region, a sea of common milkweed goes to seed.  Giant ironweed (background) also spread considerably (by seed) from the lone mother plant of 2014.

The bigleaf magnolias are finally starting to grow up.  Their steady growth in the next few years will begin to shade out  the sun-loving wildflowers, and we will start to shift to an understory of shade-tolerant ephemerals, ferns, and sedges.
October 2015, an abundance of seed remains from the coneflowers, milkweeds, wild-rye, and ironweed.  Some of the composites like New England aster (Symphyothrichum novae-angliae) provide the last flash of color this year.
Rockcastle aster
dwarf blazingstar

sweet pepperbush
common milkweed
giant ironweed

Monday, September 28, 2015

Native Plant Symposium

The Arboretum is proud to be co-hosting the 2nd annual Kentucky Botanical Symposium on October 9th and 10th.

For more details please visit the Kentucky Native Plant Society website here.

Tuesday, August 11, 2015

Passiflora in Kentucky

The genus Passiflora L. contains roughly 500 species, the majority of which are vines of pantropical distribution.  Collectively, they are the passionflowers, and their blossoms are some of the most unique and bizarrely structured in the plant kingdom.  In temperate North America where there are only ~9 spp., the flowers seem especially alien.  The name Passiflora derives from the Latin passio (passion) and flos (flower).  It was a name given by the early missionaries to South America who believed that the parts of the complex flower were different symbols of Christ’s crucifixion: five anthers represented five wounds, three styles the three nails, and the corona (the numerous fringed filaments) the crown of thorns.  

The flora of Kentucky contains just two species of passionflower, the sole representatives of the Passifloraceae family in the state.  Both are perennial vines that climb by means of tendrils, using other vegetation as a means of support to access sunlight.  These sister species occupy discrete ecological niches, and it is interesting to consider those niches as they relate to speciation.  It is also a helpful exercise with cultivation in mind, the ‘right plant, right place’ mantra – as both species can be spectacular garden plants when well-placed.

Passiflora incarnata (2014-120) in the West Knobs region
Passiflora incarnata L. directly translates to ‘flesh-colored passionflower’, though in the literature it is always referred to as ‘purple passionflower/passionvine’ or ‘maypop’.   It is widespread in Kentucky, occurring in each physiographic region but relatively sparse in the Appalachian Plateaus and Cumberland Mountains.  Purple passionflower is close to the northern extent of its range in Kentucky, being far more widespread in the southeastern United States.  At present, it is a species typically seen along rights of way and field edges; pre-settlement habitats remain enigmatic. 
The Walk Across Kentucky staff collecting in the Pennyrile region fall 2014.  The disturbed field and wooded edges here supported populations of purple passionflower.

It seems safe to say that P. incarnata prefers full sun, but will tolerate moderate shade.  Like so many species of vines and lianas, it grows masterfully in disturbed areas – and that is not necessarily a complement to the plant.  Climbers invest far less resources in their stems than other plants, as a result of their nature as structural parasites.  This allows them to grow quickly, overtopping both themselves and other species while forming a thick mass of tangled leaves and stems (think Kudzu). 

Overlapping stems of purple passionflower.  Note the two glands where the leaf meets the petiole - distinctive for this species.
Purple passionflower is especially prolific because of its propensity to sucker adventitiously from roots.  These growth aspects are worthy of note should you consider to cultivate this plant, remember that purple passionflower doesn’t ‘play well’ with other species, and the root suckers may pop up in garden beds and lawn areas nearby.  Getting rid of this plant will be no easy task.  Our plants grow up an old willow stump surrounded by turf where the mowers keep their spread at bay.

Passiflora lutea var. glabriflora (2004-003) in the Shawnee Hills region
Passiflora lutea L. is the yellow passionflower.  In Kentucky, our plants should all be the smooth form (P. lutea var. glabriflora Fern.).  While also distributed across the state, it is most prevalent along the Ohio River Valley and central Bluegrass.  It is the northernmost (and hardiest) of all Passiflora species.  Though tolerant of sun and shade, the yellow passionflower can handle the shadier end of the spectrum as compared to purple passionflower.  Our plants on the Walk Across Kentucky grow in quite dense shade, and still perform admirably.  This species is accustomed to soils more rich and moist than purple passionflower.
Yellow (left) and purple passionflower (right).  Yellow passionflower has smaller features, an entire leaf margin (vs. serrate), and rounded lobes (vs. pointed).
Where purple passionflower is big, flashy, and wild; yellow passionflower is the delicate, modest, and well-behaved of the two sisters.  Flowers of the former can be larger by an order of magnitude, and their bright-purple color is a beacon compared with the unassuming pale yellow of P. lutea.  Still, the temptation to cultivate P. incarnata may be something of a fool’s errand to be regretted later when it overruns a garden.  Yellow passionflower, if not available commercially, should be.  It would be well-placed in a shade garden, as a fine-textured and sparse groundcover, or against a tree/trellis where it may climb up to 20-30’ each season.  Along home walkways and bannisters would be an especially nice location to appreciate the subtle blossoms.
P. lutea ascending the lower limbs of an oak.  Tendrils grasp both the oak twigs and other vine stems for support.
P. lutea young leaf and flower buds

Both of our native passionflowers are valuable to wildlife, particularly the various butterflies that use them for a larval food source.  Bees are the main pollinators, and of special note is the Passionflower Bee (Anthemurgus passiflorae), a rare ground-nesting species that contributes little to pollination, but is fully obligate to the yellow passionflower – this plant is the only known species able to support the insect. 

"It has often been vaguely asserted that plants are distinguished from animals by not having the power of movement. It should rather be said that plants acquire and display this power only when it is of some advantage to them; this being of comparatively rare occurrence, as they are affixed to the ground, and food is brought to them by the air and rain. We see how high in the scale of organization a plant may rise, when we look at one of the more perfect tendril-bearers. It first places its tendrils ready for action, as a polypus places its tentacula. If the tendril be displaced, it is acted on by the force of gravity and rights itself. It is acted on by the light, and bends towards or from it, or disregards it, whichever may be most advantageous. During several days the tendrils or internodes, or both, spontaneously revolve with a steady motion. The tendril strikes some object, and quickly curls round and firmly grasps it. In the course of some hours it contracts into a spire, dragging up the stem, and forming an excellent spring. All movements now cease. By growth the tissues soon become wonderfully strong and durable. The tendril has done its work, and has done it in an admirable manner."  

Charles Darwin, 1875.