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. irio | S. altissimum | Grand Canyon specimens | Best species match |
|---|---|---|---|
| Upper cauline lvs pinnately-lobed to ± entire, lobes lanceolate to triangular | Upper cauline lvs with thread-like lobes or lflets | upper cauline lvs entire to lobed with wide lobes | S. irio |
| Upper cauline lvs with terminal lobes longer than lateral lobes | Upper cauline lvs with terminal lobes about the same size as lateral lobes | upper cauline lvs with terminal lobes longer than lateral lobes | S. irio |
| pedicel in width as wide or narrower than fruit | pedicel in width as wide or wider than fruit | pedicel in width ~narrower than fruit | S. irio |
| outer 2 sepals without horns at tip | outer 2 sepals with erect horns at tip | no horns visible | S. irio |
| petals about 1/8 inch long | petals about 1/4 inch long | petals ~4 mm long = 0.15 inch | S. irio |
| fruits 1-2 inches long | mature fruits more than 2 inches long | fruits ~30 mm long = 1.2 inches | S. irio |
| petals "brighter yellow" | petals "pale yellow to nearly white" | petals ~bright yellow | S. 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 14 September 2006, mile 0.06:
References
| Family | Brassicaceae |
|---|---|
| Scientific Name | Sisymbrium irio |
| 1987 Grand Canyon Flora Name | Sisymbrium irio |
| 1987 Grand Canyon Flora page | 38 |
| SEINet Image Page | Sisymbrium irio |
| USDA Plants | Sisymbrium irio |
| Flora of North America | |
| Jepson Manual for California treatment | Sisymbrium irio |
| Jepson Manual illustration page | 441 |
| Kearney and Peebles Name | Sisymbrium irio |
| Kearney and Peebles Page # | 336 |
| Vascular Plants of AZ name | |
| Vascular Plants of AZ volume: page | |
| Huisinga et al 2006 name | Sisymbrium irio |
| Huisinga et al 2006 page numbers | 138-139 |
| Epple Name | Sisymbrium irio |
| Epple description page # | 81 |
| Epple pix # | 329 |
| McDougall 1964 name | Sisymbrium irio |
| McDougall 1964 page # | 104 |
| Brian 2000 Name | |
| Phillips 1979 name | - |
| Phillips 1979 page # | - |
| Stockert 1967 name | - |
| Stockert 1967 page # | - |