Scarlet gaura [Oenothera suffrutescens (Ser.) W.L. Wagner & Hoch][GAACO][CDFA list: B] Photographs Map of Distribution

Scented gaura or Drummond's gaura [Oenothera xenogaura W. L. Wagner & Hoch][GAAOD][CDFA list: B] Photographs Map of Distribution

Wavy-leaved gaura [Oenothera sinuosa W. L. Wagner & Hoch][GAASI][CDFA list: B] Photographs Map of Distribution

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SYNONYMS:Complete scientific synonymy for Gaura is complex and beyond the scope of this text.

GENERAL DESCRIPTION:Noxious perennials, typically with rhizomes that produce new plants. Gaura species can colonize heavily grazed or disturbed sites in regions outside their natural range.

SEEDLINGS:scarlet gaura: Cotyledons ovate, 6-11 mm long, covered with a few minute soft hairs on the upper surfaces. Subsequent leaves elliptic, variably covered with soft hairs and tiny embedded glands. Margins smooth to wavy, often folded or loosely rolled lengthwise. No description available for scented and wavy gaura, but seedlings are probably similar to those of scarlet gaura.

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MATURE PLANT:Stems woody at the base, typically covered with short, stiff, flattened and long, spreading hairs. Leaves alternate, variable, +/- sessile, decreasing in size from the base upwards.


FLOWERS:Flowers open near sunset and wither the following morning. Racemes spike-like. Flowers irregular. Petals 4(3), white, clawed, typically fading reddish. Sepals 4(3), widely spreading, 5-14 mm long, +/- deciduous. Stamens 8, with paired teeth at filament bases. Ovaries inferior. Insect pollinated. Self-incompatible.

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FRUITS and SEEDS:Fruits erect, nut-like, 4-sided, +/- ovoid with a stalk-like base, do not open to release seeds. Differences in fruit characteristics are important for species identification. Fruit lengths given below include the base. Seeds ovoid, +/- flat-sided, 1.5-3 mm long, smooth, reddish-brown.

HABITAT:Dry grasslands in native range, but also cultivated fields, heavily grazed areas, disturbed sites, and waste places.

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PROPAGATION/PHENOLOGY:Reproduces by seed and vegetatively by rhizomes. The biology and ecology of these species is poorly documented.

MANAGEMENT FAVORING/DISCOURAGING SURVIVAL:Once established, infestations can persist. Avoiding heavy disturbance or overgrazing can prevent Gaura species from spreading.

SIMILAR SPECIES:Unlike scarlet, scented, and wavy-leaved gaura, velvetweed [Gaura parviflora Douglas] is an introduced annual with sepals 2-3.5 mm long that barely open, petals 1.5-3 mm long, and fruits that lack a stalk-like base and often point downwards. Velvetweed grows in cultivated fields, pastures, disturbed sites, and riparian areas in the South Coast and San Francisco Bay region, to 400 m (1300 ft). Gauras are closely related to Epilobium species, such as fireweed and willowherbs. Unlike the nut-like fruits of gaura, Epilobium species have capsules that split open from the tip to release seeds with a tuft of white hairs at one end.

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Prevention and control: These Gaura species are native to the Great Plains of North America, extending from Mexico to Canada. Both Robbins (1951) and The Jepson Manual state that Oenothera suffrutescens is native to California. However, these plants may become weedy in certain rangeland situations. There is little information available regarding the biology and ecology of these species. They are typically native grassland perennial herbs, which occupy dry sites, and do not appear to be negatively affected by grazing. The Jepson Manual describes oenothera xenogaura and Gaura sinuata as "rhizomatous, forming dense mats," and Oenothera suffrutescens as "woody stemmed and branched below ground." These characteristics allow these species to establish and persist in degraded range areas. Gaura coccinea has been observed to expand its native range northward into the southern interior grasslands of British Colombia. Continued expansion in California where heavy overgrazing occurs is very likely.
The key to management of these species is proper land use, before they become a problem. Avoid overgrazing dry range areas and reduce stocking rates in areas where these plants are patchy. If possible, minimize disturbance around patches to reduce the chances of spread.
Controlling established infestations is a very difficult task. Cultivation is not possible in many infested areas, and may spread rootstocks to new areas. Mowing may reduce seed production, but will not provide long-term control. Biocontrol for these plants is not a current option. Establishing competitive vegetation may prevent new seedlings from becoming established. However, these species are well adapted to grasslands and can persist in competitive healthy grassland environments.
There are certain herbicides that will provide short term control of these species. Glyphosate (2 quarts per acre) may be applied to actively growing infestations. Control may be better if applied in the fall, when then plants are actively translocating sugars to the roots. Control will be poor if plants are drought stressed or dusty. Glyphosate is a nonselective treatment and will injure or kill any other actively growing vegetation. Refer to the label for rates and precautions.

Hickman, J. C. 1993. The Jepson Manual. Higher Plants of California. Berkeley, CA: University of California Press.
Robbins, W. W., Bellue, M. K., and Ball, W. S. 1951. Weeds of California. Sacramento: California State Department of Agriculture.
Wikeem, B. M. and Newman, R. F. 1985. Range extensions of grassland species in southern iterior British Colombia. Canadian Journal of Botany 63:2240-2242.

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