Plant Species of the Bright Angel Trail:
whitetop, Cardaria draba
See Plant Guide to Bright Angel Trail for an introduction to this page, especially the Introduction To These Species Pages.
Synonym: Lepidium draba. Another common name for this species is hoary cress, which distinguishes it from Lepidium latifolium, which is also called whitetop, as well as tall whitetop, or perennial pepperweed.
This is a non-native, invasive, noxious weed, documented for the first time in the Grand Canyon in 1965 along the new railroad tracks, and now apparently known in a number of locations on the South Rim. It is one of the targets of Weed Removal on the South Rim in 2008.
Identification status: There are apparently three similar introduced species usually lumped under the name Cardaria draba; this is one of those three. Fruit were not available to distinguish which one.
Using the Kearney and Peebles key:
1. Leaves with clasping bases
2' Stem leaves clasping, not perfoliate
3 Plants perennial; basal leaves dentate; petals about twice as long as the sepals... Lepidium draba
This BLM Resource Note says that plants of this species just virtually disappear after they finish blooming and the leaves dry up. That may be why these plants were not seen on my survey in September 2007. They also may not have grown in spring 2007 due to the severe drought that season. The first picture below is followed by a link to a picture from September 2007 showing the location of these plants. The September 2007 picture was taken to show the first occurrence of Agave utahensis var. kaibabensis; it was fortuitous that it happened to show the location of the Cardaria as well.
From a SEINet search on 17 May 2008, there are two vouchers of this species from the Coconino County portion of the Grand Canyon, at: GRCA; between Santa Fe tracks and paved service road; and Colorado River mile 50.5l. Note that there may be additional vouchers at other herbaria not available through SEINet.
First occurrence on Bright Angel Trail: mile 2.42, elevation 5165 feet (1574 m).
Number of plants along Trail: at least 20 plants were found in one location in May 2008.
From 6 May 2008, mile 2.42:
This picture was taken on the right side of the trail, heading downhill, just before the switchback to the right at mile 2.43. The lower section of the trail is seen at the top of the picture. Note the pen for scale.
Compare the above picture to the one taken on 5 September 2007 from a different angle from a location a bit farther toward the switchback. You can match up the rocks lining the upper part of the lower trail for reference (the foreground rocks are outside the 2007 picture to the right). The location of the Cardaria plants is the almost completely bare area to the right of the GPS unit in the 2007 picture.
Note that the leaves in the next pictures are clasping (surrounding a portion of the stem) and dentate (having teeth pointing to the side).
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.
Copyright © 2008 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: 17 May 2008