Amur honeysuckle (Lonicera maackii) is the most widespread and arguably the most invasive of the nonnative invasive honeysuckle shrubs in Kentucky. Jeff Nelson’s article on Amur honeysuckle provides a general overview of the species. This article provides some details as to why this species is so invasive and why is an ecologically undesirable species.
Amur honeysuckle, native to central and northeastern China, Japan (rare), Korea, and far eastern Russia, occurs as an understory shrub in open hardwood and mixed hardwood-conifer forest consisting of oaks, elms and other hardwoods and fir, spruce and hemlock. It is also known from and more common in riparian and scrub communities (Luken and Thieret 1996). It grows as scattered individual shrubs or small clumps, not unlike viburnums do in Kentucky. Large, dense stands do not typically occur, but in open, riparian areas it can be weedy. In its native range, individuals typically do not exceed 4 inches diameter and 20 feet tall (Yang et al. 2011). In Kentucky, the species is often an understory shrub in open forest, but forms dense thickets at forest edge, along fence rows and in open areas. It grows larger here as well, to 6 inches diameter and 30 feet tall (personal observation).
Large Amur honeysuckle, two stems 5 inches or greater in diameter. 29 April 2020. Photo by David Taylor
This shrub leaves out early in spring, often breaking bud in mid-March, long before native trees and shrubs. By mid-April of most years, leaves are fully expanded, and the shrubs are actively growing. In the fall, Amur honeysuckle typically senesces (leaves turn yellow and drop) in late October to mid-November, and sometimes not until early December. Native trees and shrubs typically break bud late March to mid-April and do not fully expand until early May. In eastern Kentucky, they are actively dropping their leaves by mid- to late October in most years. The extra 5-8 weeks of photosynthetic activity in the honeysuckle allows it to store additional energy giving it an edge over native species (McEwan et al. 2009). It is also somewhat tolerant of late freezes. Both promote its invasive nature.
Tall Amur honeysuckle, approximately 27 feet tall. 29 April 2020. Photo by David Taylor
While Amur honeysuckle grows better in full sun (Luken 1995), it is known to survive in 1 percent of full sunlight in the heavy shade of trees (Luken et al. 1997a). The native spring flowering spice bush (Lindera benzoin) by comparison, requires about 25 % of full sun to survive (Luken et al. 1997a). Forest grown Amur honeysuckle under heavy shade tends to produce few stems which grow upward toward light specks. They tend not to have much branching, nor do they attain much diameter. In the open, individual shrubs produce numerous stems and branching is extensive. Maximum diameters are obtained in the open (Luken et al 1995a). Overtopped Amur honeysuckle shrubs respond with the production of long, upright stems that seek light. Honeysuckle in open forest may branch extensively and produce heavy shade.
Clovers are
an odd group of plants caught between agriculture and agronomy, especially in
the Bluegrass. Agronomists and cattlemen find clovers important for their
nitrogen contribution and nutritive value to livestock. Horse owners fear
clover for the fungal pathogen behind slobbers. Wildlife managers use them for
food plots. Of the roadside clovers, most came to Kentucky with settlers (Ball
et al., 2015; Bryson and DeFelice, 2009). Those red and white clovers came with
the tall fescue and Kentucky bluegrass. These species play an important role in
Kentucky agriculture; however, the horse parks and cattle farms have replaced
the natural ecosystems in the state (Noss, 2013; Campbell, 2014; Campbell, 2010).
In addition
to these introduced species, Kentucky has three prominent native clovers:
annual buffalo clover, running buffalo clover, and Kentucky clover (Vincent,
2001). Although collections of the native clovers have been made across Kentucky,
it is really very uncommon to find these populations unless one knows where
someone else has previously found it. It is unlikely that the reader will find
these species in the local park or native area.
Annual
buffalo clover (Trifolium reflexum),
is spread throughout most of the eastern United States. The beautiful blooms
have led to its potential as a horticultural species (Quesenberry et al.,
2003). Of the native clovers, the genetics of the flowering in annual buffalo
clover have been the most explored: red, white, and pink flowers (Quesenberry
et al., 2003). At one point, it was favored over naturalized white clover in unimproved
grazing lands (Killebrew, 1898).
Running buffalo clover (Trifolium stoloniferum) is a perennial species limited to the Ohio River Valley and Missouri. Plants spread on thick runners like strawberries. The species was investigated as a potential forage in the 1990s, and has been the subject of interest for herbivory dynamics in the eastern United States. The thick seed coat requires scarification in order for the seed to germinate (Kubesch, 2018; Sustar, 2017). Hoof action has been proposed as a driver in the ecology of the species, but a general disturbance regime seems necessary for the species to persist in the landscape (Kubesch, 2018). With some sandpaper and a few hours of free time, seed can be scarified. Running buffalo clover grows readily in the greenhouse.
Scrophularia marilandica (L.) and Scrophularia lanceolata (Pursh)
By Chris Bidwell
Kentucky has two native species in the genus Scrophularia
of the Scrophulariaceae/Figwort family: Scrophularia marilandica (L.) –
Eastern/Late Figwort and Scrophularia lanceolata – Early Figwort (Pursh). S.
marilandica is infrequent and primarily in Kentucky’s east-central and western
counties. S. lanceolata is to be expected as it had been reported in Carroll
County in 1986 but no further collections have since been reported. S.
lanceolata is found in six of the seven states bordering Kentucky – it is not
documented in Tennessee. Both S. marilandica and lanceolata are similar in
description, habitats, and usages. Close inspection of the flower’s stamens is
necessary to accurately identify which Scrophularia one is examining. S.
marilandica has a purple-brown sterile stamen which is longer than wide while
S. lanceolata’s sterile stamen is greenish/yellow and is wider than long. Minor
differences as blooming times of June-October for S. marilandica and May-July
for S. lanceolata can overlap and make identifying difficult from a distance.
S. lanceolata has coarser, serrated, narrower leaves and larger seed capsules.
These minor differences can be subject to interpretation which makes close
examining of sterile stamens mandatory to identify the species. One reason
Early Figwort (S. lanceotata) is overlooked may be due to the need to closely
inspect flowers – distances/terrains may discourage one from getting to the
plant to inspect accurately.
Scrophularia marilandica – Late/Eastern Figwort
Scrophularia lanceolata – Early Figwort
Both Early Figwort and
Eastern Figwort are herbaceous dicot, perennials ranging from 3-8 feet tall
with furrowed green stems. The stems do change to a woody texture and color in
late summer and persist through winter. Opposite, petioled, and serrated leaves
up to 8 inches long and 3.5 inches wide are triangular to lance shaped.
Panicled irregular flower clusters are oppositely attached at end of the stems.
Flowers are cylindrical/urn shaped 1/3- to 1/2-inch-long with an opening 1/3 of
the flower’s length. The floral formula is K(4-5)Co(5)A(5) and 6(2).
Each flower has a green calyx with 5 blunt teeth. The corolla with 5 rounded
lobes with normally a dull green exterior and a predominantly brown-purple
interior depicts Scrophularia marilandica while a reddish-brown exterior and
yellow-green interior exist in Scrophularia lanceolata. It is important to
realize however that the corolla color may vary/overlap in shades/mixes of
green, yellow, red, and brown. The corolla’s 2 upper lobes that function as a
hood keep rain/moisture from entering and diluting the rich nectar. The 2
lateral lobes help form the opening and the lower lobe curves downward serving
as an excellent landing space for pollinating insects. Five stamens are
present: 4 fertile and 1 non-fertile/sterile stamen. Scrophularia marilandica
has a reddish/purple/brown infertile stamen while Scrophularia lanceolata’s
stamen is yellow/green. These infertile stamen’ s color is the solid key to
identifying the respective species. The infertile stamen is appressed against
the upper interior posterior corolla. The 4 fertile stamens which may be fused
are at the bottom of the anterior corolla. (See accompanying photos.)
THE GENUS AGASTACHE IN KENTUCKY (Clayton – 1830’s ex Gronov. 1762)
Also known as Giant Hyssops or Hummingbird Mints has two native species in Kentucky: Agastache nepetoides (L.)-Kuntze (1891) Catnip/Yellow Giant Hyssop and Agastache scrophulariifolia (Willd.)- Kuntze (1891) Purple Giant Hyssop.
The genus Agastache is in the Lamiaceae (mint) family, subfamily nepetoideae, and the tribe mentheae. This genus was formally established in 1762 by a Dutch botanist Jan Frederik Gronovius (1690-1762) in his second edition of Flora Virginica (Linnaeus actively assisted Gronovius with this work). Flora Virginica was actually based on the notes and specimens sent to Gronovius by an English botanist John Clayton (1695-1773) while he was living in Virginia. Clayton had given the genus name to these perennial flowering herbs in the 1730’s. The second edition was published in 1762 by Grovonius’ son, Laurens (also a botanist), as the elder Grovonius had died in June of 1762. This second edition was published without Clayton’s knowledge or permission. Agastache’s author’s citation is often followed by Clayton ex Grovonius (Gronov.). Linnaeus named a genus of wildflowers – Claytonia (Spring Beauty) in honor of Clayton’s botanical contributions. Agastache (many spikes) comes from the Greek word Agan (many/very much) and Stakus/Stachys (ears /spikes of grain/wheat) which describes the plant’s “many ears/spikes” of inflorescences.
Agastache plants are aromatic flowering perennials with 21 species in North America and 1 specie in Eastern Asia. The erect/branching mint family plants range from 0.5m tall to 3m tall with square stems and opposite, petioled, coarsely toothed leaves 1-15cm wide. Aromatic inflorescences of upright spikes 2.5-15cm long resemble candles in a candlelabrum. Numerous flowers per spike are 0.6cm long. Five petals/sepals (tepals) form a tubular two-lipped flower with 2 lobes on the upper lip and 3 lobes on the lower lip. Four stamens extend beyond the flower – 2 upper stamens curve downward and 2 lower stamens curve upward. Fruit is a brown round/oval dry nutlet 1.5-2mm long with minute hairs at the squared tipped end. Flowers, which do not open at the same time, can be white, yellow, orange, red, magenta, pink, mauve, blue purple, or lavender. Plants generally thrive in moist (not wet), sun or shade, rich soil, and limestone based anthropogenic (man-made/disturbed), forest edges, talus, and rocky habitats. They are hardy in zones 3-6. Agastaches are believed to be descended from robust aromatic Asian plants which are in the Genera Dracocephalum (typical dragonheads), Lallemantia (West Asian dragonheads), Shizonepeta (Japanese catnip), and Hyssops (True hyssops). The Agastaches probably/are believed to have originated as a North American/Trans-Beringian (Laurasion distribution) offshoot about 25 million years ago (late Oligocene geologic epoch of late Paleogenic period). Debate is on-going as to Agastache lineage.
The common name, Hummingbird Mint, is from the Agastache flowers’ attraction to hummingbirds and the mint/anise aromas of their leaves. The common name, Giant Hyssop, is fairly ambiguous. Hyssop is both the classic name for genus Hyssopus and the plant Hyssopus officinalis (Hyssop) coined by Lineaus in 1753. Hyssop is a Eurasian (southern Europe/western Asian) aromatic mint with 4 stamens, square stems, and narrow/lanceolate opposite leaves. Hyssop can be used as an adjective to describe leaves that tend to be narrow/oblong/lanceolate – as Eupatorium hyssopifolium – commonly known Hyssop Leaf Eupatorium or Thoroughwort. Interestingly, Hyssop or a “Hyssop-like” plant is mentioned in the Bible – 10 times in the New Testament and 2 times in the Old Testament. The Hebrews identified the plant as Ezov or Ezob while the Greek translation of this plant was Hyssop. Both the Hebrew and Greek name of this plant mentioned in the Bible probably share a common but unknown origin. Hyssopus officinalis (Hyssop)(L.) is not the Hyssop mentioned in the Bible as it is a southern European/western Asian species and was unknown in Palestine at these earlier biblical dates. Biblical scholars cite Origanum syriacum (Syrian Hyssop), a close relative to oregano and majoram, as most likely the Hyssop mentioned in the Bible. Other scholars believe that a mustard plant, caper (Capparis spinosa), or a mint family plant (Origanum maru), is the Biblical Hyssop. The issue is not resolved as to the actual identity of the “hissop” so important to Hebrew purification rites. Why Linnaeus chose Hyssopus (hyssop) for the genus name of these earlier mints now in the Agastache genus was probably based on several botanical/taxonomy factors of that time (plant structure, appearance, and sex organ(s) composition).
There are two native species of Agastache in Kentucky: A. nepetoides (L.) 1753-Kuntze (1891), Yellow Giant Hyssop and A. scrophulariifolia Willd. (1801)-Kuntze (1891), Purple Giant Hyssop. Agastache nepetoides is an infrequent FACU (Facultative Upland) plant found occasionally in wetlands (1-33%) and dry to mesic open woods and woodland borders across Kentucky. Greenish-yellow flowers are present (see photos). Agastache scrophulariifolia is a rare historical (not observed since 1980) plant in the Appalachian plateaus and interior low plateaus. Flower colorations range from white to blue/purple (see photes). Both these mint family plants have square stems, opposite leaves, and are aromatic. Both bloom July through October and stalks can remain standing through the winter. Flower colors are yellow for A. nepetoides and mainly blue/purple flowers for A. scrophulariifolia. Flower colorization can readily distinguish these two species. Other subjective differences can/may also assist in the identities:
A. nepetoides – Yellow Giant Hyssop 2-5 feet tall square stems – may be slightly winged smooth stem weakly aromatic calyx – 1-1.5 mm with ovate lobes
A. nepetoides – Yellow Giant Hyssop
A. scrophulariifolia – Purple Giant Hyssop 3-6+ feet tall no winged stems minute hairs on stem strongly aromatic calyx – 2-2.5 mm – with lanceolate lobes
A. scrophulariifolia – Purple Giant Hyssop
Agasstache nepetoides has other common names: catmint, catnep, catnip for its aromatic scent similar to catnip (Nepeta cataria). Yellow Giant Hyssop may also be referred to as calmint/calamint for its medical usages in tea or as a conserve (undried vegetables mixed with sugar and blended to form a soft mass) for a “calming” effect in treating “hysterical” complaints, seizures, stomachaches, and colic.
The species name nepetoides (L.) Yellow Giant Hyssop is Latin based meaning resembling Nepeta (catmint). The origin of nepetoides may be from several sources. Nepeta is Latin for catnip/catmint and was used by Linnaeus in 1738 as the genus name for catnip – “nepeta floribus interrupte spicatis pedunculatis” (nepeta with flowers in a stalked interrupted spike).
An Italian city named Nepi, Nepet, or Nepete that was well-known for having a “catnip” plant with a less aromatic/enticing scent could also be the source of nepeta. Finally Nepa is Latin for a water scorpion whose sting was treated by the Yellow Giant Hyssop may also play a as the species name.
Agastache scrophulariifloria’s (Purple Giant Hyssop) other common names are Lavender Hyssop, Anise Hyssop, Prairie Hyssop, Horsemint, and one unusual moniker – Figwort/Pilewort. Figwort is from Old English words Fig meaning piles (hemorrhoids) and an Old English word wort meaning plant usually possessing medicinal usages – thus Figwort/Pilewort is a plant to treat hemorrhoids. (Several other plants may also go by Pilewort: fireweed (Erechtite hieraciifolia) and lesser celadine (Ranunculus ficaria). Purple Giant Hyssop specie’s name scrophulariifolia is from two Latin words – scrofula (meaning swelling of the lymph nodes in the neck due to tuberculosis) and folia (meaning leaves). This plant was used to treat scrofula associated with tuberculosis. Scrophularia is a genus in the family Scrophulariaceae (Figwort family with 200 species) and both are also derived from the Latin word scrofula. Interestingly both these Agastaches, Yellow and Purple Giant Hyssops, have the previous binomial genus name of hysspus – Hyssopus nepetoides (L.) (1753) and Hyssopus scrophulariifolia Willd. (1801). – (Carl Ludwig Willdenow (1765-1812), a German botanist/taxonomist – a founder of Photogeography: Study of Geographic Distributions of plants).
In 1891 Otto Kuntze, ((1843-1907) a German botanist, placed the genus Hyssopus, whose plants are called Giant Hyssops or Hummingbird mints, into the genus Agastache (Clayton ex Gronovius) probably based on Agastache leaves being more of “catnip” leaf shape, structure, and aromatic scent. Controversy still exists and with DNA sampling/testing expect more taxonomic changes.
Both the Purple and Yellow Giant Hyssops have medicinal, horticultural, culinary, and other usages that are interchangeable among the species. China has used Giant Hyssops for several centuries. With some 30+ known compounds, the Purple and Yellow Giant Hyssops have demonstrated anti-viral, anti-polio, anti-cancer, antiseptic, anti-inflammatory, antifungal, antioxidant bioactivity. Usage in AIDS and hypertension have shown promise. Ongoing research continues. Use of oils of mints in general must be used judiciously and safely – even in low doses (2-3 drops) can cause seizures and other serious complications especially in younger children. One should always consult their doctor before trying any mint oil preparation. Use during pregnancy is not advised. Native Americans used Giant Hyssops leaves and flowers in teas to treat colds, ague, fever, colic, cough, worms, rheumatism, and as an expectorant and a carmiative (anti-flatulence). They used leaves/flowers in poultices for bruises, rashes, itching, stings, swelling, and as an astringent. Native Americans used conserves for migraines, seizures, and as a “calming” agent. The Meskwaki used a Giant Hyssop infusion as a diuretic and the Iroquois/Cherokee used it for poison ivy rash and itching. Agastache scrophulariifolia specifically was used for hemorrhoids.
Culinary usages include Giant Hyssops leaves/flowers in soothing, calming, aromatic teas, as potherbs in salads, and a seasoning agent in soups/stews and other meal preparations. Seeds were made into meal. Giant Hyssop honey was viewed as a special delicious treat.
Horticultural and manufacturing usages of Giant Hyssops revolve around their economic importance. Agastache nepetoides and A. scrophulariifolia plants, seeds, rootstocks, and their cultivars are sold by nurseries and trade companies as ornamentals for landscaping, and as proven attractors for bees, butterflies, and hummingbirds so valuable for garden/crop pollination. The many pollinators are rewarded with the Hyssops rich nectar and pollen. Giant Hyssops are a favorite with beekeepers. Giant Hyssops combine/mix in nicely as companion plants to black-eyed susans (Rudbeckia), blazing stars (Liatris), and sunflowers (Heliathus). These tall beautiful native wildflowers provide valuable resources and aesthetic appeal to man and fauna.
Folklore practices concerning Giant Hyssops has dried plants hung in the home as having powers to drive out evil and negativity. Floriography has Agastache plants with symbolic meanings of cleanliness, holiness, healing powers, protection from evil, spiritual cleaning, and body-spirit protection.
Propagation of Giant Yellow and Purple Hyssops can be by seeds (after cold stratification), rhizomes, rootstocks, and spring cuttings. They can also self-pollinate which may explain their heterozygosity. Hyssops transplant readily in early stages. Seed dispersal is achieved by seed/nutlet eating birds as goldfinches, wrens, and sparrows. Wind may also disperse seeds by utilizing the hyssop seed’s hairs as airfoils or as “feathers”. Both Agastache nepetoides and scrophulariifolia are resistant to moderate drought and heat; tolerant of most soils except persistently wet habitats; and need full sun in warm climates (zones 3-6). Plants need limited competition especially from non-natives. Giant Hyssops are deer resistant and are not affected by the alleopathic capability of walnut trees. Agastaches are threatened by habitat loss, theft, extreme drought/heat, flooding, and natural succession. Giant Hyssops normally last 3-4 years.
Agastache nepetoides (Giant Yellow Hyssop) and A. scrophulariifolia (Giant Purple Hyssop) are two native Kentucky species that need our protection. These towering, robust, beautiful plants are not only aesthetic but useful to man and fauna. Look for Giant Hyssops in summer and fall. Marvel at their beauty and protect their habitats. One author caught up in Hyssops virtues/horticultural usages stated “A towering specimen in the shade garden, not for meek and mild. Do Not plant near mid/low height plants. Do plant near that jackass neighbor”!! I’ll end this paper on this whimsical thought provoking statement.
Chris Bidwell – Naturalist, past president KSNH Mary Alice Bidwell – typing Susan Wilson – photography
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