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Detailed Area Plant List for Cottonwood Open Space (City of Golden), Jefferson County, United States.
Edited by Tom Schweich
This list is assembled from personal collections, herbarium vouchers, and published lists that were available at the time this list was prepared. There may be additional species of plants in this area that were unknown or undocumented at the time this list was prepared. For California, much of the data is provided by the participants of the Consortium of California Herbaria as indicated by a single dagger “†.” Their web site is at: (http://ucjeps.berkeley.edu/consortium/). For Colorado, much of the data is provided by the Southwest Environmental Information Network as indicated by a double dagger “‡,” which web site is found at (http://swbiodiversity.org). See their respective websites for copyright information and recommended citation formats.
For a complete list of Locations included in this Area List, see the Locations Included section, below. For a check list, please see: Check List for Cottonwood Open Space (City of Golden), Jefferson County, United States.
Apiaceae
Conium maculatum L. Common Poison Hemlock. Weed: CO DofA, List: C. CalPhotos. Jepson eFlora. SEINet Taxon.
- Cottonwood Natural Area,
3951.
12/27/2024.
.
 Coll. No. 1436, Conium maculatum |
Asclepiadaceae
Asclepias speciosa Torr. Showy Milkweed. CalPhotos. Jepson eFlora. SEINet Taxon.
- Cottonwood Natural Area,
3945.
12/27/2024.
.
 Showy Milkweed (Asclepias speciosa). |
 Seed pod of Asclepias speciosa |
 Seed of Asclepias speciosa |
Asteraceae
Brickellia eupatorioides (L.) Shinners. False Boneset. CalPhotos. Jepson eFlora. SEINet Taxon.
Perennial herb,
to 40 cm.;
Leaves,
alternate,
short-petioled (2 mm.),
48 mm. × 7 mm. wide,
lanceolate,
tip obtuse,
margin entire,
glandular-punctate, sparsely strigose;
Inflorescence,
corymbiform,
heads in groups of 4-5;
Involucre,
8.5 mm. × 6 mm. wide;
Phyllaries,
3+ series,
graduated,
2-8.5 mm. × 0.5 mm. wide,
prominently veined “longitudinally striate,”
margin scarious,
tip acuminate to spinulose;
Receptacle,
epaleate;
Disk flowers,
#19,
corolla, 7 mm., yellow;
Pappus,
plumose bristles,
6 mm.;
Cypsela,
many ribs (maybe 10).
(Described from Coll. No. 1553, 1 Sep 2016.)
- Cottonwood Natural Area,
3946.
12/27/2024.
.
.
Heterotheca villosa (Pursh) Shinners. (Syn: H. v. (Pursh) Shinners var. nana (A. Gray) Semple , H. v. (Pursh) Shinners var. villosa ) Hairy False Goldenaster. CalPhotos. Jepson eFlora. SEINet Taxon.
Perennial herb, to 50 cm.; Leaves, cauline alternate, entire, 1-veined, distal perpendicular to stems, hairs > glands; Heads solitary, with both ray and disk flowers; Phyllaries in 2+ series, unequal, to 7 mm.; Rays, 9 mm.; Pappus double, outer narrow scales ≤ 1 mm. (easier to see on mature fruit), inner bristles, 6.5 mm., white; Fruit, disk 3 mm., hairy.
- Cottonwood Natural Area,
3953.
12/27/2024.
.
.
Onopordum acanthium L. Scotch Cottonthistle. Weed: CO DofA, List: B. CalPhotos. Jepson eFlora. SEINet Taxon.
- Cottonwood Natural Area,
3956.
12/27/2024.
.
 Coll. No. 2772, Onopordum acanthium |
Brassicaceae
Lepidium draba L. (Syn: Cardaria draba (L.) Desv. ) White Top, Hoary Cress. Weed: CO DofA, List: B. CalPhotos. Jepson eFlora. SEINet Taxon.
Perennial, herb, to 45 cm., spreading by rhizomes, hairs simple; Leaves, basal, not seen, cauline, sessile, base auriculate, 36 mm. × 12 mm. wide, oblanceolate, margin irregularly toothed, reduced above; Flowers, petals, white; Style, immature, 1 mm.; Fruit, silicle, immature, 1.3-1.5 mm. × 0.5-1.0 mm. wide, flattened, wings 0, glabrous, reticulate-veined (Described from Coll. No. 1366, 24 May 2016).
- Cottonwood Natural Area,
3957.
12/27/2024.
.
 White Top plants arising from a rhizome. |
 Habitat of Coll. No. 1366, Lepidium draba |
 Coll. No. 1874, Lepidium draba |
 Coll. No. 1366, Lepidium draba |
 Fruit of Coll. No. 1874, Lepidium draba |
Cactaceae
Opuntia macrorhiza Engelm. Western Pricklypear. CalPhotos. Jepson eFlora. SEINet Taxon.
Perennial cactus, not distinctly mat-forming; Stem, segments, 90 mm. × 60 mm. wide, flattened, bluish-green, areoles, #5-6 per diagonal row, spaced 8-14 mm., proximal, glochids only, distal, glochids and spines, spines, #2, #1, 28 mm., erect, brown to tan at tip, #1, 12 mm., recumbent, nearly white; Flowers, petals, 36 mm. × 22 mm. wide, wedge-shaped, color yellow; Stamens, many, 18 mm., yellow; Style, 20-24 mm., stout; Stigma, lobes, #6-8, 3 mm.; Fruit, 38 mm. × 17 mm. wide, narrow at base, fleshy, green, areoles, mix of glochids and short spines. (Described from Coll. No. 1948, 15 June 2018.)
- Cottonwood Natural Area,
3948.
12/27/2024.
.
 Coll. No. 2371, Opuntia macrorhiza |
 Opuntia macrorhiza on Schweich Hill. |
 Obs. No. 1540, Opuntia macrorhiza |
 Coll. No. 1948, Opuntia macrorhiza |
Rosaceae
Crataegus . Hawthorn. CalPhotos. Jepson eFlora. SEINet Taxon.
- Cottonwood Natural Area, 3947. 12/27/2024. .
Salicaceae
Populus deltoides Marshall ssp. monilifera (Aiton) Eckenw. (Syn: Populus sargentii Dode ) Plains Cottonwood. CalPhotos. Jepson eFlora. SEINet Taxon.
- Cottonwood Natural Area,
3958.
12/27/2024.
.
.
Salix exigua Nutt. Coyote Willow, Narrow-Leaved Willow. CalPhotos. Jepson eFlora. SEINet Taxon.
Perennial erect shrub, to 2 m.; Leaves, alternate, 21 mm. ×. 1.8 mm. wide, 11.7 ×long as wide, abaxial villous, adaxial mostly glabrous, margins entire, slightly revolute; Staminate catkins, 30 mm. × 6 mm. wide; Pistillate catkins, 42 mm. × 4 mm. wide, floral bract, 1.8 mm., capsule, 2.6 mm., glabrous (Described from Coll. No. 1880, 24 May 2018).
- Cottonwood Natural Area,
3949.
12/27/2024.
.
 Pistillate catkin of Coll. No. 1880, Salix exigua |
 Staminate catkin of Coll. No. 1880, Salix exigua |
Scrophulariaceae
Verbascum thapsus L. Common Mullein. Weed: CO DofA, List: C. CalPhotos. Jepson eFlora. SEINet Taxon.
- Cottonwood Natural Area,
3954.
12/27/2024.
.
 Package of Mullein in the Pharmacy at Fort Hartsuff. |
 Dense colonies of Common Mullein (Verbascum thapsus) in Cottonwood Canyon |
 Collection No. 512, Verbascum thapsus |
Solanaceae
Solanum dulcamara L. Climbing Nightshade. CalPhotos. Jepson eFlora. SEINet Taxon.
- Cottonwood Open Space (City of Golden),
Several patches on the overgrown bank of ditch.
Cottonwood Open Space, formerly named Cottonwood Natural Area, was designated by the City of Golden in July 2025.
Right bank of the Welch Ditch in the western corner of Cottonwood Open Space, 1.63 km. south of the GNIS location of Golden.
Tom Schweich 3446.
7 Jul 2025.
(
FLD
KHD
OBI
REGIS
)
.
 Coll. No. 1961, Solanum dulcamara |
 Coll. No. 1961, Solanum dulcamara |
 Coll. No. 3446, Solanum dulcamara. |
Asparagaceae
Yucca glauca Nutt. Soapweed Yucca. CalPhotos. Jepson eFlora. SEINet Taxon.
- Cottonwood Natural Area,
3960.
12/27/2024.
.
 Yucca glauca “Soapweed Yucca” on Dakota Ridge. |
Poaceae
Agropyron cristatum (L.) Gaertn. Crested Wheat Grass. CalPhotos. Jepson eFlora. SEINet Taxon.
- Cottonwood Natural Area,
3959.
12/27/2024.
.
.
Bromus inermis Leyss. (Syn: B. inermis Leyss. ssp. inermis ) Smooth Brome. CalPhotos. Jepson eFlora. SEINet Taxon.
Perennial grass to 1 m., rhizomatous; Leaves, sheath, 8-11 cm., closed, ligule, <1 mm., membraneous, blade, 12-17 cm × 0.5 cm., flat, soft, with a distinguishing fold, usually described as an “M” or a “W” that is difficult to see when dry; Inflorescence, panicle, 15 cm. × 4 cm. wide, multiple 1° branches per node, mostly on one side of rachis; Spikelets, 1 per node on 1° and 2° panicle branches, 15-24 mm. × 5 mm. wide, laterally compressed, 2-6 florets per spikelet; Glumes, 2, keeled, glabrous, lower, 7-8 mm., veins 1 upper, 8-10 mm., <lowest floret; Rachilla, sparsely hairy on abaxial side, extended beyond uppermost floret or not; Callus, small, glabrous; Lemma, 11-12 mm., veins, 3, 5, 7, obvious, tip bifid, some awned; Awn (when present), 1.0-1.6 mm., arising near tip of lemma; Palea, 9 mm., veins ciliate. (Described from Coll. No. 1113, 26 May 2014, and Coll. No. 1219, 16 Jul 2015).
- Cottonwood Natural Area,
3955.
12/27/2024.
.
.
Festuca ovina L. Complex, hybrid or selection. CalPhotos. Jepson eFlora. SEINet Taxon.
- Cottonwood Natural Area, 3961. 12/27/2024. . .
Sorghastrum nutans (L.) Nash. Yellow Indian Grass. CalPhotos. Jepson eFlora. SEINet Taxon.
Perennial warm season grass, to 1.2 m.; Inflorescence, panicle, 12 cm., color distinct yellowish; Spikelets, paired (theoretically), sessile spikelet present, pedicellate spikelet absent leaving a hairy pedicel; Compression, ±dorsal (upper glume flattened); Glumes, 6 mm., ±equal, veins 7 prominent green, upper glabrous, lower hairy; Florets, 2 per spikelet, lower floret reduced and sterile, upper floret perfect; Lemma, 4.5 mm., membraneous, apex bifid and awned, awn, 12 mm., twisted, bent once; Palea, reduced or missing; Stamens, 3, 4 mm., yellow; Stigmas, 2, feathery, pink (turning brown?). (Described from Coll. No. 1249, 26 Jul 2015).
- Cottonwood Natural Area, 3950. 12/27/2024. .
| Total number of taxa: | 17 |
| Native Taxa: (serif, italic, bold) | 8 |
| Non-native Taxa: (sans-serif, italic) | 8 |
| Nativity Undetermined: (default font, italic) | 1 |
| Listed Weeds: Identified as Weed | 4 |
Notes:
† -- Data provided by the participants of the Consortium of California Herbaria (ucjeps.berkeley.edu/consortium/).
‡ -- Southwest Environmental Information Network, SEINet. 2009-2014. http//:swbiodiversity.org/seinet/index.php. Accessed from July 2009 to September 2014.
Locations Included in This Area
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Date and time this article was prepared: 11/3/2026 12:18:25 PM.
