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    According to BONAP, we have ten species of Descurainia species in the Four Corners area. They are not easy to separate. Intermountain Flora states, "Species of Descurainia in western North America exhibit a wide range of variability, making distinctions between them difficult. Because of their weedy disposition and the abundance of disturbed habitats from human activities, they are often brought together and possibly interbreed. The greatest difficulties in identification are with D. incisa and D. pinnata, two confusingly polymorphic taxa".

     Botanical keys distinguish the species from one another on the basis of the number of divisions in their leaves, the shape and length of their fruits ("siliques"), the amount of hairiness and kind of hairs (straight or forked), and the length of the fruit pedicels. Altitude can also assist in identifying species as a just a few are found in the subalpine and alpine.

    Descurainia sophia is a non-native; the others are native.

    The Descurainia genus was named by Philip Webb and Sabin Berthelot in the mid-1800s.  Francois Descurain, 1658-1740, was a French botanist and pharmacist.

Descurainia incana

Descurainia incana (Mountain Tansy Mustard)
Brassicaceae (Mustard Family)

Semi-desert to subalpine. Disturbed areas, meadows. Spring, summer.
El Diente Trail, July 22, 2004.

The flowers of this Mustard are quite small but they are in relatively large, terminal clusters. The plant is slender, tall, and has bright green, finely cut leaves.  Descurainia incana is found in montane and higher altitudes in Colorado, New Mexico, and Utah.

The plant was first described and named (probably "Descurainia richardsonii") by Bernhardi and then was renamed Descurainia incana by Dorn. "Incana" is Latin for "gray".

Descurainia incana

Descurainia incana (Mountain Tansy Mustard)
Brassicaceae (Mustard Family)

Semi-desert to subalpine. Disturbed areas, meadows. Spring, summer.
El Diente Trail, July 22, 2004.

Two key distinguishing characteristics of D. incana are flattened seed pods and appressed pods (clasping the stem).  In the photograph at left, the pods can be seen clasping the stem as the plant grows taller and new flower clusters bloom.

Descurainia obtusa

Descurainia obtusa (Blunt Tansy Mustard) 
Brassicaceae (Mustard Family)

Semi-desert. Sandy shrublands, opening. Spring.
Near Bluff, Utah, May 2, 2007.

Descurainia obtusa is fairly common through several counties in New Mexico and much more common in Arizona but it has only recently been discovered in Montezuma County, Colorado and San Juan County, Utah.  Leaves and fruit are rounded (obtuse) at their tips, and the fruit (in Mustards called a "silique") is abruptly contracted at its tip and somewhat at its base.  Flowers are minute but clustered so they do attract attention.

Edward Greene first named this plant Sophia obtusa around the turn of the 19th/20th century; it was renamed by Otto Schultz early in the 20th century.

Descurainia obtusa

Descurainia obtusa (Blunt Tansy Mustard) 
Brassicaceae (Mustard Family)

Semi-desert. Sandy shrublands, opening. Spring.
Near Bluff, Utah, May 2, 2007.

Descurainia sophia

Descurainia sophia (Flixweed Tansy Mustard) 
Brassicaceae (Mustard Family)

Semi-desert to subalpine. Woodlands, shrublands, opening. Spring.
Canyons of the Ancients National Monument, April 1, 2005.

In many woodland areas Descurainia sophia is a very common spring plant, often found in dense patches, sometimes scattered over large areas, but it also can be solitary.  The finely cut leaves appear early in the spring and are followed by a long, lanky plant topped with a tight cluster of numerous, tiny, bright yellow flowers.  Petals are only 2-3 millimeters long.  The stem and leaves are often thickly clothed in a mass of very small, twisted, and often branched hairs.  The petals are sparsely hairy. 

Descurainia sophia is a weedy, alien plant but a close inspection will show delicate leaf structure, lovely flowers, and very cute siliques (seed pods).  The plant has a noticeably rank smell.

Linnaeus gave this species its original name of Sisymbrium sophia in 1753, and Philip Webb gave it its present name which was published by Kark Prantl in 1891. "Soph" is Greek for "wise" or "skillful", perhaps an allusion to the plant's many (supposed) medicinal uses.

Descurainia sophia

Descurainia sophia

Descurainia sophia (Flixweed Tansy Mustard) 
Brassicaceae (Mustard Family)

Semi-desert to subalpine. Woodlands, shrublands, opening. Spring.
Near Canyons of the Ancients National Monument, May 23, 2011 and
May 27, 2015.

In woodland areas Descurainia sophia most often occurs as scattered single plants or in small groupings; in an open meadow it can spread into colonies of hundreds of plants.

Flowers mature quickly, the plant elongates, and seed pods (siliques) grow rapidly to 15-30 mm long but only .5-1 mm wide. Mature siliques are often constricted (torulose), especially noticeable on the whole silique at lower far right. Pedicels (the stems of the seed pods) are 4-17 millimeters long.

Descurainia sophia

Descurainia sophia (Flixweed Tansy Mustard) 
Brassicaceae (Mustard Family)

Semi-desert to subalpine. Woodlands, shrublands, opening. Spring.
Near Canyons of the Ancients National Monument, May 23, 2011.

Leaf shape is often used in keys to separate one species of Descurainia from another, but leaf shape varies considerably in each species and overlaps the shape of leaves in other species. Specifically the problem is in the number of divisions in each leaf. All Descurainia have leaves that are at least pinnate, i.e., once cut into leaflets. Many can be cut again and again. The leaves at left are cut twice.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Descurainia incana

Range map for Descurainia incana

Range map for Descurainia obtusa

Range map for Descurainia sophia