Oenothera biennis [Common Evening Primrose]

[Andrea B.]

Blum, A.G. (2013) Oenothera biennis L. (Onagraceae) Common Evening Primrose. Flowers photographed in ultraviolet and visible light. http://www.ultraviol...ening-primrose/

 

Route 35, Middletown, New Jersey

Lat [N40°24'31.0"] Lon [W74°07'52.1"]

21 September 2013

Wildflower

 

Synonyms:

• Weedy Evening-primrose
  
• Oenothera biennis ssp. centralis Munz
  
• Oenothera biennis var. pycnocarpa (Atkinson & Bartlett) Wieg.
  
• Oenothera muricata L.
  
• Oenothera pycnocarpa Atkinson & Bartlett
  

Pollinator: Thought to be pollinated by night flying hawkmoths.

 

Comment:

O. biennis is the source of evening primrose oil which is thought to be beneficial for some skin conditions such as eczema. Other medicinal uses are found in Native American practices and non-traditional medicine.

The flowers open in the evening and remain partially open for part of the next day.

In the UV O. biennis has very UV-bright petals with some UV-black veining and a UV-black central star around the UV-dark anthers and stigma.

 

Reference:

1. Newcomb, L. (1977) Common Evening Primrose, page 134. Newcomb's Wildflower Guide. Little, Brown & Co., New York City, NY.


2. 1. Natural Resources Conservation Service (2013) Oenothera biennis Plant Guide. US Department of Agriculture. http://plants.usda.gov/plantguide/pdf/cs_oebi.pdf

 

Equipment [Nikon D600-broadband + Nikon 105mm f/4.5 UV-Nikkor]

 

Visible Light [f/11 for 1/200" @ ISO 100 in Sunlight with Baader UVIR-Block Filter]

 

Visible Light [f/8 for 1/200" @ ISO 400 in Sunlight with Baader UVIR-Block Filter]

The top-heavy cluster of pods has pulled the stalk down onto the asphalt.

 

Visible Light [f/8 for 1/400" @ ISO 400 in Sunlight with Baader UVIR-Block Filter]

The weedy sprawling O. biennis grows happily at the edge of the parking area.

 

Ultraviolet Light [f/11 for 1/125" @ ISO 400 with SB-14 UV-modified Flash and Baader UV-Pass Filter]

 

Ultraviolet Light [f/11 for 1/125" @ ISO 400 with SB-14 UV-modified Flash and Baader UV-Pass Filter]

A very tiny moth is seen on the underside of the flower. Note that this side also shows UV-dark veining and central area.

 

Ultraviolet Light [f/11 for 1/125" @ ISO 400 with SB-14 UV-modified Flash and Baader UV-Pass Filter]

[nfoto]

I am surprised your specimen has so restricted area of the UV-dark centre and UV-dark veins. My samples have much larger UV-dark appearance, but do share the very UV-bright petals.

[Andrea B.]

Subspecies variation ? And then too, my flowers are not completely open.

The last photo (just posted) shows a slightly more open flower where you can see more of the dark center.

[nfoto]

My flowers had at least twice the size of the dark spot and much more pronounced veins in UV.

 

Taxonomy of this genus is convoluted and there is evidence of ongoing new species formation. My plants fit the description of O. biennis as given in Nordic literature. The latest Flora of Norway (Lid & Lid, 2005) specifically gives a green stem all the way into the inflorescence as a character for its identification. Single, stiff upright and chiefly unbranched stems also is mentioned as a character. The species is biennial and has a basal rosette that persist into its second year. The visual appearance of your plants, seen in the last picture of the opening post, is strongly at variance with the plants I know as O. biennis. The stems are clearly branched and look almost woody so would indicate a perennial plant. Thus, perhaps having a different UV signature is to be expected?

[Andrea B.]

I am looking at my keys again today, so we will track this one down and figure it out. :)

 

I will start with the New England Wildflower Society's online Oenothera key: https://gobotany.new...dkey/oenothera/

While this key is for New England, it tends to cover NJ wildflowers well enough. And will suffice to give me an initial "feel" for Oenothera.

 

**************************************************************

 

NEWS Oenothera Key

 

1a.

zygomorphic (no)

fruit indehiscent (no)

This leads to

• O. curtiflora, the Small-flowered Bee-blossom, which is pink.
  Native to central/west US. Intro to N.Eng.
  
• O. filiformis, the Bee-blossom.
  Native to centra/midwestern US. Intro to N.Eng.
  
• O. gaura, the Biennial Bee-blossom, which is white.
  Native to east US. Intro to N.Eng.
  

1b.

actinomorphic (yes)

fruit dehiscent (yes)

You can see the pods splitting in this (slightly blurry) foto crop.

1b leads to 12 species: O.biennis, fruticosa, glazioviana, grandiflora, lacinata, nutans, oakesiana, parviflora, perennis, pilosella, serrulata, villosa.

 

4a.

ovary quadrangular in x-section (no)

capsule sharply quadrangular to 4-winged, tapering to base (no)

This leads to

• O. fruticosa, the Narrow-leaved Evening-primrose.
  Native to east N.Am. Rare in N.Eng. Orange stamens & ribbed pods (Peterson).
  
• O. perennis, the Little Evening-primrose.
  Native to east N.Am.
  
• O. pilosella, the Meadow Evening-primrose.
  Native to east N.Am. Intro to N.Eng.
  

4b.

ovary more or less round (terete) in x-section (yes)

capsules roundish to quad, round/truncate at base (yes)

While this foto does not show a cross section, you can see that the ovary seems to be roundish ??

Capsules are shown above in the first post.

4b leads to 9 species: O.biennis, glazioviana, grandiflora, lacinata, nutans, oakesiana, parviflora, serrulata, villosa.

 

7a.

stigmas peltate (no) with 4 short rounded lobes (no)

hypanthium funnel-shaped (no)

calyx lobes prominently keeled (no)

stamens alternately of different size

This identifies

• O. serrulata, the Yellow Evening-primrose
  Native to central N.Am. Rare in N.Eng.
  

7b.

stigmas with 4 linear lobes (yes)

tubular hypanthium, terete in x-section (yes, see 4b above)

calyx lobes scarcely lobed or not lobed (yes, some tiny fingers in the pre-bud)

stamens all of similar size (yes, see Visible & UV fotos in first post)

7b leads to 8 species: O.biennis, glazioviana, grandiflora, lacinata, nutans, oakesiana, parviflora, villosa.

 

8a.

leaf & bract blades prominently dentate to pinnatifid (no)

capsules of uniform width (no)

seeds (?)

plants annual (?)

This identifies

• O. lancinata, the Cut-leaved Evening-primrose
  Native to east N.Am. Intro to N.Eng. Invasive in other continents !!
  

8b.

leaf & bract blades entire to dentate (yes)

capsules widest at base, tapering to apex (yes)

seeds (?)

plants biennial or short-lived (?)

8b leads to 7 species: O.biennis, glazioviana, grandiflora, nutans, oakesiana, parviflora, villosa.

 

THIS NEXT POINT IN THE KEY IS KEY. B) Exserted anthers or not ??

ALSO what is a "sepal appendage" ?? OK, those are the little fingers at the end of the calyx/sepals.

 

9a.

stigmas exserted beyond the anthers (no)

petals approx 30-45mm long, say, one & a-half inches (?)

anthers approx 10-15mm long, say, half an inch (?)

sepal appendages approx 5-9mm long (?)

This leads to

• O. glazioviana, the Garden Evening-primrose
  Probably originated as a European cultivar. Introduced to N.Am.
  Coastal in the US and some scattered interior states.
  
• O. grandiflora, the Large-flowered Evening-primrose
  Native to SE US and not to Europe as some authors have it.
  Rare in N.Eng.
  

9b.

stigmas surrounded by or shorter than the anthers (yes)

petals approx 7-25mm long, say quarter-inch to an inch (?)

anthers approx 3-10mm long, say one-eighth inch to slightly less than one-half inch (?)

sepal appendages approx .5-6mm long, say less than a quarter-inch.

[need a couple of other fotos here to show the stigma/anther relationship]

This leads to 5 species: O. biennis, O. nutans, O. oakesiana, O. parviflora, O. villosa

 

11a.

sepal appendages subterminal, separated in bud (no)

true apex represented by small lobe (no)

[after viewing an example on O.parviflora foto which shows a little lobe bump just before the end]

inflorescence sometimes curved near apex (no)

• O. oakesiana, the Oakes' Evening-primrose
  Native to northeast N.Am and coastal plains/dunes.
  
• O. parviflora, the Small-flowered Evening-primrose
  

11b.

sepal appendages terminal (yes) together in bud (yes)

inflorescence straight and erect (yes)

The sepal appendages characterization was difficult.

In the swelling bud, my sepal appendages are convivant,

but in the "pre-bud" they are separated. [need foto here]

This leads to 3 species: O. biennis, O. nutans, O. villosa

 

OH GOODY the HAIRS are next !!! :) :D

 

13a.

plants densely and minutely strigose

sometimes with spreading, pustulose hairs on stem (yuk!)

sometimes with glandular hairs on the inflorescence

This identifies

• O. villosa, the Hairy Evening-primrose.
  It is indeed quite hairy and has glandular hairs.
  Native to central N.Am. and some parts of N.Eng.
  

13b.

plants variously pubescent (4 characterizations)

pustulose-based hairs, gland-tipped hairs, sparse tiny strigose hairs OR nearly glabrous

I am going with sort of a general non-dense hairiness.

This leads to 2 species: O. biennis, O. nutans

 

14a.

axis (main stem) of inflorescence definitely hairy (yes)

green deciduous bracts of inflorescence 12-50 x 8-25mm in size (got the darker green)

[need foto to show hairy stalk]

This identifies

• O. biennis, the Common Evening-primrose
  Native to all but western US and Canada.
  

14b.

axis (main stem) of inflorescence glabrous or near so (no)

pale green caducous bracts of inflorescence 10-25 x 2-8mm in size (no to pale green)

[after viewing example of paler green bracts on O. nutans fotos]

This identifies

• O. nutans, the Nodding Evening-primrose
  Native to east N.Am.
  

**************************************************************

Jepson eFlora Key for Oenothera: http://ucjeps.berkel...IJM.pl?key=9766

 

**************************************************************

 

Remarks from Field Guides

 

O.biennis by Kershaw, MacKinnon, Pojar in Plants of the Rocky Mts.

• Grayish-hairy or reddish-hairy; stems single, stiffly erect;
  
• 30-150cm tall; often branched; stout taproots.
  
• Leaves narrowly lance-shaped to oblong, 2-15 cm long,
  stalked near base, stalkless upwards on stem.
  
• 4 backward-bending sepals at the tip of a 3-5cm long calyx tube (hypanthium).
  
• Several fragrant flowers in long, dense clusters (spikes).
  
• Fruit erect, hairy spindle-shaped capsules 2-4 cm.
  

O.biennis by Peterson in Wildflowers

• Leafy, rough-hairy, often reddish-stemmed, reflexed sepals
  
• Branched, 1-5 feet tall.
  

O.biennis by Newcomb in Wildflower Guide

• Pods 4 times longer than broad
  
• Leaves lance-shaped, alternate, wavy-edged, slightly toothed.
  
• 1-6 feet high
  

O.biennis by Lady Bird Johnson Wildflower Center (http://www.wildflowe...p?id_plant=OEBI)

• At the top of a leafy stalk bloom lemon-scented, large yellow flowers.
  
• biennial with leafy, branched stems from a basal rosette.
  
• The bright-yellow, four-petaled flowers, up to 2 inches across, open at night.
  
• These fragrant flowers occur in a many-flowered, terminal spike.
  

**************************************************************

Oenothera species in New Jersey, USDA

 

Subspecies not included.

Black = not in preceding key.

Grey = ruled out from preceding key.

Oenothera biennis

Oenothera cinerea

Oenothera clelandii

Oenothera fruticosa

Oenothera glazioviana

Oenothera grandiflora

Oenothera grandis

Oenothera humifusa

Oenothera laciniata

Oenothera mollissima

Oenothera nutans

Oenothera oakesiana

Oenothera parviflora

Oenothera perennis

Oenothera pilosella

Oenothera villosa