Tuesday, October 31, 2017




Figure 1: Passiflora incarnata commonly called "Maypops" or Purple Passionflower.


Passiflora is a genus of approximately 5131 species mostly found in the semi-tropics and of tropics Central and South America. Most species are vines, but shrubs, trees and herbaceous species also exist. The plants are grown extensively for their beautiful and unique flowers, edible fruits in some species, and foliage. Horticulturists have produced many hybrids and cultivars. According to Weakly 2, North Carolina is home to two native Passiflora species, P. incarnata and P. lutea.

All Passiflora flowers have highly modified and unique flower morphology. Starting from the center of the flower there is a central column of tissue known as the androgynophore that elevates and supports both the male and female reproductive structures. In Passiflora incarnata this includes five anthers, a superior 3-locular ovary, and three large stigmas. Surrounding the base of the androgynophore is a ring of short filaments called the operculum. The operculum partially covers and hides floral nectaries encircling the androgynophore. Next is a corona made up of numerous thin filaments usually brightly colored. Then there are five petals and five sepals. Depending on the species, the sepals may or may not have awns on their tips. Lastly, some species may also have 3 glandular bracts on the peduncle 3 (Figure 1, 2, 3).

Figure 2: Side view of Passiflora incarnata showing the unusual flower morphology.

Figure 3: Notice the three glandular bracts on the peduncle being attended by ants.

Probably the best known of the two species in North Carolina is Passiflora incarnata more commonly known as Maypops, or Purple Passionflower (Figures 4). It is common across the state and is found in open disturbed areas such as old fields, pastures, fence rows, and roadsides. The large purple flowers bloom through-out the summer and into fall and produce both pollen and nectar. They are pollinated by various insects but primarily by carpenter bees (Figure 5, 6). The vine rambles across the surrounding vegetation and supports itself with tendrils. The alternate, deeply palmately 3-lobed leaves have serrated margins and the petioles have a pair of extra-floral nectaries (Figures 7,8,9). Late in the fall large green to yellowish egg-shaped fruits (berries) can be seen hanging from the vines (Figure 10). Supposedly, the popping noise made by stepping on these fruits is what gave rise to the common name ‘Maypops’. Passiflora incarnata and other Passiflora species are also critical host plants for various Lepidoptera especially, especially the Gulf Fritillary, Agraulis vanilla (Figures 11, 12, 13).

Figure 4: Top view of Passiflora incarnata flower.

Figure 5: Passiflora flowers produce both nectar and pollen that attracts a variety of pollinators.

Figure 6: Notice how the carpenter bee has to brush under the anther to reach the nectaries at the base of the androgynophore. 
Figure 7: Notice the alternate palmately lobed leaves with serrated margins.

Figure 8: Passiflora incarnata has extra-floral nectaries on the petioles.
Figure 9: A close-up of the extra-floral nectaries. Notice the ants feeding at the nectaries and the Gulf Fritillary, Agraulis vanillae larva.

Figure 10: Fruits of Passiflora incarnata, Purple Passionflower.

Figure 11: This was one of many Gulf Fritillary, Agraulis vanilla, larvae I observed feeding on my Passiflora vine this summer.

Figure 12: A Gulf Fritillary, Agraulis vanilla, larva forming its chrysalis.

Figure 13: An adult Gulf Fritillary, Agraulis vanilla.

Our second native Passiflora species is Yellow Passionflower, or Passiflora lutea.  Although this plant is also common and widely spread across the state it is not as well-known as Purple Passionflower. The smaller and less brightly colored flowers of P. lutea make it easy to overlook (Figures 14, 15, 16, 17). Yellow Passionflower is also a vine but unlike P. incarnata it can tolerate more shaded areas and is often found along wood margins, thickets, and in open forests. It also spreads vegetatively by long slender rhizomes. The leaves are shallowly palmately lobed (usually three lobes) with entire margins and the petioles lack nectary glands (Figure 18). The plants bloom late summer and into the fall and produces small dark blue-purple-black fruits (Figure 18, 19). 
Figure14: An illustration of Passiflora lutea. USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York. Vol. 2: 565.

Figure 15: Looking down onto a Passiflora lutea flower giving an especially nice view of the corona filaments. Photo by Doug Goldman, hosted by the USDA-NRCS PLANTS Database.

Figure 16: Another view of a Passiflora lutea, Yellow Passionflower flower.

Figure 17: A nice side view of a Yellow Passionflower flower showing the short filaments of the operculum around the elongated androgynophore. Notice the superior ovary underneath the spreading stigmas.

Figure 18: A nice view of the shallowly lobed leaf and an immature fruit from Passiflora lutea.

Figure 19: A mature fruit of Passiflora lutea. Photo by Doug Goldman, hosted by the USDA-NRCS PLANTS Database.

These two species are easily identified by flower color and size but there are other notable differences between Passiflora incarnata and P. lutea (Table 1).

Table 1: A summary of Passiflora incarnata and P. lutea characteristics 4

Passiflora incarnata
Passiflora lutea
Yellow Passionflower
Vine with tendrils
Vine with tendrils
Alternate, palmately lobed and veined leaves, with serrated margins
Alternate, palmately lobed and veined leaves, with entire margins
Petioles have nectar glands
Petioles do not have nectar glands
Floral bracts present
Floral bracts absent
Sepals have awns
Sepals do not have awns
Petals purple
Petals pale green-yellow

Fruits green to yellowish
Fruits purple-black

The origin of the name ‘Passiflora’ is thought to have originated from early Spanish explorers and missionaries in the Americas. When they saw the unique morphology of Passiflora flowers it reminded them of Christ’s crucifixion. So ‘Passiflora’ or Passionflower, is derived from the Latin passio, for "suffering, enduring”, and Flora, for "goddess of flowers" 5 As a child growing up in the ‘Bible Belt’ I was taught the religious symbolism associated with Maypop flowers. The table below gives an example of how some people interpret the various plant parts with the crucifixion 6 (Table 2 ).

Table 2: Christian Symbolism of Passiflora Flowers



Whips used to beat Christ before his crucifixion
Hammer, or Holy Grail
3 Stigmas
Nails used to hang Christ form the cross
5 anthers
Wounds on Christ’s body
Coronal filaments
Crown of thorns placed upon Christ’s head
10 petals and sepals
The ten faithful apostles (minus Peter the denier and Judas the betrayer)
Purple color
The color of royalty, Christ the King
Red color
The blood of Christ

I hope you have enjoyed learning about our native Passiflora species. I encourage people to plant these wonderful vines because;
  1.  they are beautiful and interesting plants/flowers,
  2.  they provide nectar and pollen to native pollinators,
  3.   they serve as host plants to a large variety of butterflies,
  4.  and their fruits provide food to local animals and birds.


1. “The Plant List — A working list for all plant species.” Passiflora - The Plant List, www.theplantlist.org/1.1/browse/A/Passifloraceae/Passiflora/. 

2. Weakley, Alan S. Flora of the Southern and Mid-Atlantic States. Chapel Hill, NC: University of North Carolina Herbarium, North Carolina Botanical Garden, University of North Carolina, Chapel Hill, 2015. Print.

3. Magazine, Garden Design. “Botanic Notables: 500 Shades of Passiflora - Garden Design.” GardenDesign.com, Garden Design Magazine, 25 Feb. 2016, www.gardendesign.com/flowers/passion.html. 

4. Goldman, Douglas H., and John M. MacDougal. “Passiflora.” Flora of North America @ efloras.Org, www.efloras.org/flora_page.aspx?flora_id=1.

5. Graves, Julia. The Language of Plants: A Guide to the Doctrine of Signatures. Lindisfarne Books, 2012.

6. “Flora | Search Online Etymology Dictionary.” Index, www.etymonline.com/search?q=flora.

7. Unless otherwise noted, all photographs were taken by and are property of Tracie L. Jeffries.

Saturday, October 28, 2017

Series I: Confusing N.C. Ferns


Cinnamon Fern vs. Interrupted Fern

North Carolina is home to many diverse species of ferns ranging from minute filmy ferns to large ferns such as Royal fern, Osmunda regalis, which can easily top 100 centimeters (3.3 feet) in height1. In the North Carolina mountains two of our more common larger fern species can be easily confused with each other if sori are not present. This article will focus on how to identify and distinguish between Cinnamon Fern, Osmundastrum cinnamomeum and Interrupted Fern, Osmunda claytoniana. (See Table 1, 2).

Table 1: Historical and Current Taxonomic Treatment

Common Name(s)        
Radford & Bell 2
Flora of North  America 3 (1993)
Weakley 4 (2015)

Cinnamon Fern

Osmunda cinnamomea L.
Osmunda cinnamomea L.
Osmundastrum cinnamomeum (L.) C. Presl

Interrupted Fern

Osmunda claytoniana L.
Osmunda claytoniana L.
Osmunda claytoniana L. var. claytoniana

Table 2: Table of general characteristics for Cinnamon Fern and Interrupted Fern. Note that shared traits between the species are in bold type.

Cinnamon Fern
Osmundastrum cinnamomeum
Interrupted Fern
Osmunda claytoniana L. var. claytoniana
Large coarse ferns
up to 3 feet +
Large coarse ferns
up to 3 feet +

Plants grow from a short, stout, rhizome resulting in a large clump of fronds
Plants grow from a short, stout, rhizome resulting in a large clump of fronds
Blades one pinnate-pinnatifid

Blades one pinnate-pinnatifid


Dimorphic – separate sterile and fertile fronds

Dimorphic – separate sterile and fertile pinnae

Pinnae margins entire

Pinnae margins entire

Wooly tufts of hairs (trichomes) underneath blade in axis of pinna and rachis
Wooly tufts absent

Cinnamon fern, Osmundastrum cinnamomeum, is commonly found across the state in a large variety of wet habitats such as wet ditches, swamps, bogs, and mesic woodlands. It is a large coarse fern with one pinnate-pinnatifid blades (Figure 1). The fronds form large clumps that grow out from short stocky rhizomes. Individual plants can range from to 90 up to 150 centimeters (3-5 feet) in height. The fern is dimorphic, meaning that the fertile fronds look different from the sterile fronds. Fertile fronds have highly modified pinna with large globose sporangia. The sporangia start off green but quickly turn a rusty brown color, hence part of the reason for the common name ‘Cinnamon’ fern (Figure 2, 3, 4 ). The fertile fronds form early in the spring and quickly wither. 

Figure 1: This is an example of a fern frond that is one pinnate pinnatifid. Notice the initial frond divisions or pinnae are subdivided (pinnate) but not  deep enough to produce distinct and completely separate pinnules (pinnatifid).

Figure 2: A nice example of Cinnamon Fern, Osmundastrum cinnamomeum, notice the large size, dimorphic fronds, and concentrated growth habit from the short thick rhizome.     
Figure 3. Another example of a Cinnamon Fern showing the fertile frond surrounded by sterile fronds.

Interrupted ferns, Osmunda claytoniana, are commonly found in the mountains of North Carolina. They are also large coarse ferns with one pinnate-pinnatifid blades. They average about 90 cm. in height (3 feet). Like Cinnamon ferns they are also dimorphic. The fertile fronds resemble the sterile fronds except the center pinnae are modified and have clusters of large globose sporangia. When young the sporangia are green but turn brown-black at maturity. Similar to the Cinnamon Ferns the fertile pinnae quickly wither leaving a gap in the middle of the frond. No other fern has this unique arrangement of sporangia in the center of the blade hence the common name ‘Interrupted Fern’ (Figures 4, 5, 6). I also commonly find large populations of Interrupted Fern where no plants have produced fertile pinnae. I believe the short-lived nature of the Cinnamon Fern’s fertile frond and the lack of fertile pennae on numerous Interrupted Ferns is what leads many to confuse these two fern species with each other, especially later in the year.

Figure 4: A nice example of Interrupted Fern, Osmunda claytoniana. Notice the fertile pinnae in the center of the frond with sterile pinnae above and below.

Figure 5: A close up of Interrupted Fern fertile pinnae that are young and still green. Picture is courtesy of the National Park Service.

Figure 6: Fertile Interrupted Fern pinnae after they have matured and turned brown.

However, several factors can help to distinguish between them. Cinnamon fern will have wooly tufts of trichomes in the axils between the rachis and pinnae, interrupted fern does not (Figures 7, 8). But, be careful because late in the summer these trichomes can wear away so another feature to look at is the tip of the blade. Cinnamon ferns have tapered acute tips while interrupted ferns have very blunt tips (Figures 9,10, 11). Also, consider the habitat. Cinnamon Ferns prefer moister habitats than Interrupted Ferns. For example, in the South Mountain State Park there is a trail that transverses a slope. Interrupted Fern is abundant along the trail and upper regions of the slope where the soil is well drained. But, as one travels down the slope towards a small creek, Interrupted Fern becomes less prominent and is eventually replaced by a large population of Cinnamon Fern in the flatter, moister areas along the water. 

Figure7: Cinnamon Fern, Osmundastrum cinnamomeum, showing the distinct tufts of trichomes at the pinnae - rachis junction.

Figure 8: Interrupted Fern, Osmunda claytoniana, showing the lack of trichomes at the pinnae - rachis junction.

Figure 9: This is a close-up of Cinnamon Fern pinnae showing the accuminate-acute tips.

Figure 10. This is a close-up of Interrupted Fern pinnae showing the more obtuse-rounded tips.

Figure 11: Interrupted Fern is on the left and Cinnamon Fern is on the right. Notice the overall more blunt and rounded ends of the Interrupted Fern frond and pinnae compared to the more accuminate-acute ends of the Cinnamon Fern frond and pinnae.

Cinnamon and Interrupted ferns are the two most commonly seen large ferns in the North Carolina mountains. They can be easily identified by looking at the differences in fertile fronds (if present), differences in blade tips, and looking for the presence or absence of trichomes at the pinnae-rachis axis.


1. Morin, Nancy R. Flora of North America North of Mexico Volume 2: Pteridophytes and Gymnosperms. New York, NY: Oxford U Press, 1993. Print.

2. Radford, Albert Ernest, Harry E. Ahles, and Clyde Ritchie Bell. Manual of the vascular flora of the Carolinas. Chapel Hill, NC: U of North Carolina Press, 1983. Print.

3. Weakley, Alan S. Flora of the Southern and Mid-Atlantic states. Chapel Hill, NC: U of North Carolina Herbarium, North Carolina Botanical Garden, U of North Carolina, Chapel Hill, 2015. Print.

4. Hardy Fern Library. N.p., n.d. Web. 14 July 2017. <http://hardyfernlibrary.com/ferns/home.cfm>.

5. All photos, unless otherwise noted, were taken by and are property of Tracie Jeffries.