Plant Species of the Bright Angel Trail:
See Plant Guide to Bright Angel Trail for an introduction to this page, especially the Introduction To These Species Pages.
Synonym: Ranunculus testiculatus.
Non-native, introduced to Arizona sometime before 1963, and apparently spreading.
This species is a very widespread weed on the Bright Angel Trail, ranging from the South Rim down to at least 4400 feet elevation, and almost always occurs in a dense population. This is undoubtedly due to the large number of seeds produced by each plant.
I observed a population of this species in September 2003 at about 5580 feet elevation, so it has been present well below the Rim at least since then.
Identification status: 100%, using the key in the Flora of North America treatment of Ranunculus:
1' Leaves simple and lobed.
9' Stems erect.
14' Petals yellow; fruits achenes, unwinged.
15 Cauline leaves absent, tuberous roots absent; leaves not compound.
16 Plants villous; sepals 3-6 × 1-2 mm, persistent in fruit; fruit wall firm, smooth, beak much longer than achene body. ... R. testiculatus
R. testiculatus is the only species present so far in North America in Ranunculus Subgroup Ceratocephalus.
See the Flora of North America description and illustration. The description says:In North America, Ranunculus testiculatus seems to be expanding its range rapidly in arid and semiarid areas. A second species of this subgenus, R. falcatus Linnaeus [Ceratocephala falcata (Linnaeus) Persoon], has been reported from North America, but all reports seem to be based on misidentified material of R. testiculatus.
From a SEINet search on 10 May 2008, there are eight vouchers of this species from the Coconino County portion of the Grand Canyon. The nearest are at: South rim Grand Canyon. Picnic grounds; and South Rim Grand Canyon, in front of District Ranger Office Building. Note that there may be additional vouchers at other herbaria not available through SEINet.
The first voucher of this species at the Grand Canyon was in 1963. It has not yet been vouchered from below the Rim, even though it is now abundant there, at least along the Bright Angel Trail.
First occurrence on Bright Angel Trail: mile 0.00, elevation 6845 feet (2086 m).
Number of plants along Trail: at least 99 plants were found in at least 9 different locations (the maximum recorded abundance for each quantity) in May 2008.
The following pictures show the plant getting progressively older. The petals are yellow at full bloom, but quickly turn to white and are deciduous. By the time the fruit has fully developed, the structure of the flower is no longer clear unless one recognizes that the dense heads are a dense group of achenes from a single flower.
From 5 and 6 May 2008, miles 0.00-0.04:
From 7 May 2008 near the Visitor Center:
The huge number of tiny plants covering the foreground half of this picture are all C. testiculata. It is possible that the fairly isolated plants at the edges of the distribution are the leading edge of the invasion, and those areas will be dense with plants in the future. As can be seen from the closeup of the fruit above, each flower from each plant produces ~20 seeds.
Similar dense collections are present on some hillsides along the Bright Angel 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.
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: 10 May 2008