Plant Species of the Bright Angel Trail: Wright's thelypod, Thelypodium wrightii
See Plant Guide to Bright Angel Trail for an introduction to this page.
Identification status: high confidence.
It took me a while to get the correct determination, especially since I had never seen or heard of a Thelypodium species before. Leafing through picture books didn't help, since no one had its picture.
Trying to key it out in my hotel room after I first saw this species on 5 September 2007 didn't work. I at first assumed it was a Brassicaceae, since that is what it looked like, but it wouldn't key out using the McDougall key.
When I returned to the field on 6 September 2007, the first thing I did was count its stamens. Unfortunately, for some reason, the first flower I examined had only five stamens, not the usual six for the Brassicaceae family. I spent some time in the field trying to key it with the McDougall key. That time was spent off in weird-family-land, those few families with four petals and five stamens, but I couldn't find a match.
I then looked at a few more flowers, and found some with six stamens.
At home, even when I tried Brassicaceae, it wouldn't key in McDougall since it doesn't fit three characteristics given in his key elements!
The bad key elements in McDougall are the first two here:17a. Calyx closed or nearly so when the flower is in bloom, the sepals spreading, if at all, only at the tip. 18b. Petal blades not flat, either crisped, channeled or hood-shaped, little if any wider than the basal portion. 21b. Fruits not flattened or only slightly so. 23b. Petals white; stem leaves sessile. 24b. Sepals spreading or turned downward at blooming time.... Thelypodium wrightii
Note that key element 24b contradicts key element 17a, and that the sepals for T. wrightii are indeed spreading in their entirety, which McDougall correctly states in his description. This is the only species of Thelypodium in Arizona with spreading sepals. Also, even though many Thelypodium species do indeed have crisped petal blades, T. wrightii does not; it has flat petal blades. Finally, T. wrightii very clearly has petal blades that are wider than the basal portion, as do the other Thelypodium species with similar oblanceolate petals.
After struggling with the determination for quite a while, I finally got the correct determination simply by looking at pictures online for every Brassicaceae species on the Grand Canyon plant list for the area around this trail.
I of course then groaned at the three errors in the key. Finding such errors in a key is, by the way, not an unusual situation for any key. It is very difficult to make a good key that works for all species, due to the numerous exceptions to the rule found within each genus.
By the way, it must not be unusual to find fewer than six stamens in these flowers. Look at the two flowers shown in closeup view in the bottom two pictures on this page. The relative position of the camera and the flowers is shifted slightly between the pictures, eliminating the possibility that any stamen is hidden from view in both pictures. The uppermost flower has only four stamens, and the lowermost flower has six stamens. Of course, I don't know whether the flower with only four stamens originally had six, and lost two as the flower aged, or if the flower only had four stamens originally.
From a SEINet search, there are 13 vouchers of this species from the Coconino County portion of the Grand Canyon, including one from the famous Alice Eastwood in 1913 from this trail. Note that there may be additional vouchers at other herbaria not available through SEINet.
First occurrence on Bright Angel Trail: mile 0.00, elevation 6845 feet (2086 m).
Number of plants along Trail: Only about 10 plants were found in 3 different locations in September 2007. More might be present in a wetter year.
All pictures are from 5 September 2007. The plants with flowers at the trailhead are a bit off-trail, down a steep slope, so couldn't be photographed up close, but there was a young rosette present next to the trail that is most likely the same species. These plants are in the shade of the Pinus edulis at the trailhead. From mile 0.00:
These plants were found a very short distance farther along the trail:
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 Thelypodium wrightii 1987 Grand Canyon Flora Name Thelypodium wrightii 1987 Grand Canyon Flora page 39 SEINet Image Page Thelypodium wrightii USDA Plants Thelypodium wrightii Flora of North America Jepson Manual for California treatment Jepson Manual illustration page Kearney and Peebles Name Thelypodium wrightii Kearney and Peebles Page # 329 Vascular Plants of AZ name Vascular Plants of AZ volume: page Huisinga et al 2006 name - Huisinga et al 2006 page numbers - Epple Name - Epple description page # - Epple pix # - McDougall 1964 name Thelypodium wrightii McDougall 1964 page # 106 Brian 2000 Name Phillips 1979 name - Phillips 1979 page # - Stockert 1967 name - Stockert 1967 page # -
Copyright © 2007 by Tom Chester.
Permission is freely granted to reproduce any or all of this page as long as credit is given to me at this source:
Comments and feedback: Tom Chester
Last Update: 24 September 2007