Plant Species of the Bright Angel Trail: herb sophia, Descurainia sophia
See Plant Guide to Bright Angel Trail for an introduction to this page, especially the Introduction To These Species Pages.
Important note: In September 2007, I originally keyed these plants out to the native Descurainia pinnata, which turned out to be incorrect. I got misled by a stem on a plant that managed to survive the summer, which was not representative of this species. When I saw normal plants in April 2009, it was clear that the correct determination was the non-native Descurainia sophia. I have not yet changed the text below to reflect that determination. But it certainly explains why I was troubled by the shape of the fruit in 2007!
Identification status: high confidence.
The keying in McDougall Cruciferae (=Brassicaceae) is as follows:1b. Fruits with many seeds 3b. Fruits not flattened 11b. Fruits much longer than wide 16b. Fruit not long-stalked within the calyx (not Stanleya) 17b. Calyx open when the flower is in bloom, the sepals spreading 25b. Fruits not flattened 33b. Fruits spreading 35a. Plants with forked or star-shaped hairs 36b. Plants with pinnate leaves 37b. Upper leaves once-pinnate; fruits 3/4 inch long 38b. No determination in #39 (D. richardsonii only at North Rim; fruit of D. californica too short) 40b. Fruit very weakly club-shaped; seeds ~20 (~10 per chamber) ...D. pinnata
The other choice in couplet 40 is D. obtusa, which is also ruled out because both ends of the fruit are not tapered abruptly, and the style is not 0.5-0.8 mm.
The subspecies was obtained from the Jepson Manual key:4' Pedicel in fr 60-90° from infl axis; herbage hairs dense 5 Lf lobes or lflets obtuse at tip, oblanceolate to obovate ...ssp. glabra
In September, most specimens of this taxon have long ago dried up, and looked like the old flower stalk in the bottom picture below. I would not have been able to get the determination of this species if there hadn't been one plant that had managed to survive the summer, and was blooming and fruiting again. Thank you, little plant, for surviving!
From a SEINet search, there are 18 vouchers of the species (including ones not determined to a subspecies) from the Coconino County portion of the Grand Canyon, including a voucher of the species (not determined to a subspecies) from an unspecified location on this trail. There is also a voucher of the species from SHRINE OF THE AGES CHAPEL, elevation 7000 feet. Note that there may be additional vouchers at other herbaria not available through SEINet.
Only two of the 18 vouchers are determined to a subspecies. Those two are both ssp. halictorum, found at an unspecified location on the Grand View Trail and the North Kaibab Trail at 2800 feet. The closest voucher determined as ssp. glabra is in Hualapai Canyon, Plants of Havasupai Canyon at an unspecified location.
Kearney and Peebles state ssp. halictorum and ssp. glabra occur throughout most of the range of the species in Arizona.
First occurrence on Bright Angel Trail: mile 0.01, elevation 6845 feet (2086 m).
Number of plants along Trail: at least 20 plants were found in at least 3 different locations in September 2007. More specimens would probably be present in a wetter year.
From 5 September 2007, mile 0.06:
From 6 September 2007, mile ~0.13:
In the following picture, note the many dead stalks (more were cropped out of this picture) surrounding the single stalk with blooms and fruit):
The following picture shows the septa (membranes dividing the ovary chambers) left on an old flowering stalk, along with some newly-developed flowers below:
If you aren't already familiar with the appearance of branched and stellate hairs, you won't be able to easily recognize them in the following picture. But if you are familiar with them, you can recognize the hairs being well-separated, and wider at the top, than if they were single hairs.
It takes some imagination to agree with McDougall that these fruits are more or less club-shaped. Only the uppermost fruit in the following picture could possibly fit that description. In fact, the Jepson Manual says the fruit can be oblong for this species as well, which is how I would normally describe it.
See Resources for Grand Canyon Flora for further information on most of these references. Entries in the second column are either the name used in that source or a page reference. The name is linked to online pages when available. If a given reference does not contain this taxon, the entry is either left blank or contains a hyphen.
Family Brassicaceae Scientific Name Descurainia pinnata ssp. glabra 1987 Grand Canyon Flora Name Descurainia pinnata ssp. glabra 1987 Grand Canyon Flora page 37 SEINet Image Page Descurainia pinnata ssp. glabra USDA Plants Descurainia pinnata ssp. glabra Flora of North America Jepson Manual for California treatment Descurainia pinnata ssp. glabra Jepson Manual illustration page (419) (shows ssp. halictorum) Kearney and Peebles Name Descurainia pinnata ssp. glabra Kearney and Peebles Page # 349 Vascular Plants of AZ name Vascular Plants of AZ volume: page Huisinga et al 2006 name Descurainia pinnata Huisinga et al 2006 page numbers 138-139 Epple Name - Epple description page # - Epple pix # - McDougall 1964 name Descurainia pinnata McDougall 1964 page # 102 Brian 2000 Name Phillips 1979 name - Phillips 1979 page # - Stockert 1967 name - Stockert 1967 page # -
Copyright © 2007-2012 by Tom Chester.
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Last Update: 20 June 2012