Plant Species of the Bright Angel Trail: Sisymbrium irio

This is a non-native species.

See Plant Guide to Bright Angel Trail for an introduction to this page.

Characteristics

Identification status: high confidence.

Group: Dicot
Family: Brassicaceae
Habit: Annual
Grand Canyon Nativity: Non-Native

First occurrence on Bright Angel Trail: mile 0.06, elevation 6800 feet (2070 m).

Number of plants along Trail: Only about 10 plants were found in 3 different locations in September 2007.

When I first saw these plants in September 2006, I concluded they were Sisymbrium irio. However, I became wary of that determination due to the elevation ranges given in Phillips et al 1987. S. irio was said to be only along Hermit Trail and Havasu Canyon, below 4000 feet, whereas S. altissimum was given at 3100-7500 feet. Since the elevation here is 6800 feet, one would expect the determination to be S. altissimum.

Normally there is no problem at all distinguishing these two species, since they differ in a number of characteristics (see the table below), especially in the cauline leaves. Unfortunately, the plants seen here in September 2006 and September 2007 are depauperate, and essentially have no stem at all and hence no cauline leaves.

Fortunately, detailed analysis clearly shows that the determination of these plants is indeed S. irio. The following table gives the distinguishing characteristics of S. irio and S. altissimum, compared to these plants:

S. irioS. altissimumGrand Canyon specimensBest species match
Upper cauline lvs pinnately-lobed to ± entire, lobes lanceolate to triangularUpper cauline lvs with thread-like lobes or lfletsupper cauline lvs entire to lobed with wide lobesS. irio
Upper cauline lvs with terminal lobes longer than lateral lobesUpper cauline lvs with terminal lobes about the same size as lateral lobesupper cauline lvs with terminal lobes longer than lateral lobesS. irio
pedicel in width as wide or narrower than fruitpedicel in width as wide or wider than fruitpedicel in width ~narrower than fruitS. irio
outer 2 sepals without horns at tipouter 2 sepals with erect horns at tipno horns visibleS. irio
petals about 1/8 inch longpetals about 1/4 inch longpetals ~4 mm long = 0.15 inchS. irio
fruits 1-2 inches longmature fruits more than 2 inches longfruits ~30 mm long = 1.2 inchesS. irio
petals "brighter yellow"petals "pale yellow to nearly white"petals ~bright yellowS. irio

The first four characteristics come from the Jepson Manual; the last three come from McDougall. The observed characteristics all come from the pictures below, except for the pedicel width comparison to the fruit width that was determined in the field.

Every characteristic goes to S. irio.

A search for vouchers removed my concern about S. irio just being a low-elevation species. There is a voucher from the Grand Canyon, South Rim, one mile south of Desert View at 7300 feet (GRCA 72220). There are also vouchers in California from the White Mountains at 11,600 feet, and from the San Bernardino Mountains at 8100 and 5700 feet.

Note that this doesn't mean that the elevation range in Phillips et al 1987 was incorrect; it probably means that S. irio was expanding its range, as non-native taxa unfortunately often do.

These plants certainly look a bit different from the low elevation specimens in my southern California yard, being much shorter and with somewhat different leaf shapes. However, Jane Strong points out that specimens of a number of species get shorter and look different at higher elevation.

Pictures

From 5 September 2007, mile 0.06:

From 14 September 2006, mile 0.06:

References

FamilyBrassicaceae
Scientific NameSisymbrium irio
1987 Grand Canyon Flora NameSisymbrium irio
1987 Grand Canyon Flora page38
SEINet Image PageSisymbrium irio
USDA PlantsSisymbrium irio
Flora of North America
Jepson Manual for California treatmentSisymbrium irio
Jepson Manual illustration page441
Kearney and Peebles NameSisymbrium irio
Kearney and Peebles Page #336
Vascular Plants of AZ name
Vascular Plants of AZ volume: page
Huisinga et al 2006 nameSisymbrium irio
Huisinga et al 2006 page numbers138-139
Epple NameSisymbrium irio
Epple description page #81
Epple pix #329
McDougall 1964 nameSisymbrium irio
McDougall 1964 page #104
Brian 2000 Name
Phillips 1979 name-
Phillips 1979 page #-
Stockert 1967 name-
Stockert 1967 page #-


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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:
http://tchester.org/gc/plants/species/sisymbrium_irio.html
Comments and feedback: Tom Chester
Last Update: 29 September 2007