blue toadflax

(Nuttallanthus canadensis)

Conservation Status

IUCN Red List

not listed


N5 - Secure

S3 - Vulnerable


Special Concern

blue toadflax
Photo by Leanne Hinke

Blue toadflax is an early season prairie wildflower. It is native to North America, Mexico, and western and southern South America. It is sometimes cultivated as an ornamental. It was introduced and is naturalized in Japan, North and South Korea, eastern Russian Federation, and the Indian subcontinent. In the United States it is common in the south and on the East Coast. It is uncommon in the southeast and metro regions of Minnesota, where it is at the northwestern extent of its range, and it is absent from the remainder of the state. It is found in prairies, old fields, roadsides, and disturbed sites. It grows under full sun in dry, sandy soil.

Blue toadflax is an annual forb that rises on two kinds of stems from a small taproot. First to appear is a radiating cluster (rosette) of a few to several vegetative stems. Vegetative stems are to 2 long (1 to 6 cm) long, hairless, and usually unbranched. They usually lay flat on the ground (prostrate), sometimes with just their tips ascending (decumbent). Some may eventually reach 4 (10 cm) in length with age. Later, one to four flowering stems emerge. Flowering stems can be 4¼ to 27½ (11 to 70 cm) tall but are usually no more than 20 (50 cm) in height. They are usually erect, but sometimes curve upward very near the base (strongly ascending), and are usually unbranched, but sometimes have a few branches near the tip. They are hairless below the inflorescence. Both kinds of stems are slender, round, and green to reddish-green. Vegetative stems are often withered or absent at flowering time.

Leaves on vegetative stems are opposite or in whorls of three, 116 to ½ (2 to 12 mm) long, and 164 to (0.5 to 3.0 mm) wide. They may be stalkless or on short leaf stalks. The leaf blades are narrow and inversely egg-shaped or elliptic. Leaves on flowering stems are alternate, unstalked, 316 to 1 (5 to 43 mm) long, and 164 to 116 (0.5 to 2.2 mm) wide. The leaf blades are linear or thread-like. Leaves of both kinds of stems are unlobed, hairless, and untoothed.

The inflorescence is a slender, up to 7 (18 cm) long, unbranched arrangement (raceme) of flowers at the end of the flowering stem. The flowers are widely spaced on the raceme, even at the start of flowering time. Each flower is on a 132 to ¼ (1 to 7 mm) long, erect or strongly ascending stalk (pedicel). At the base of the pedicel there is a single 132 to ¼ (1 to 7 mm) long, linear, bluntly pointed, modified leaf (bract).

The flowers have both male and female reproductive parts (perfect). They bloom from mid-May to mid-June. Each flower is 516 to ½ (8 to 13 mm) long including the spur. There are 5 outer floral leaves (sepals), 5 petals, 4 stamens, and 1 style. The sepals, together referred to as the calyx, are united at the base then separated into 5 narrow, sharply pointed, 116to (2.1 to 3.5 mm) long lobes. They are green to purplish-green and sometimes hairless but more often glandular-hairy toward the base. The petals, together the corolla, are light blue to light purplish-blue. They are united at the base then separated into two unequal lips. The upper lip is 132 to 116 (1.2 to 2.0 mm) long, sometimes a little longer, and divided into two equal lobes. The lobes are erect or slightly angled backward. The lower lip is 116 to ¼ (2 to 5 mm) long and is divided into three rounded, spreading lobes. The base of the lower lip is white and strongly arched. A nectar spur extends backward from the throat of the corolla. The spur is 116 to ¼ (2 to 7 mm) long and may be straight or curved. The stamens are arranged as two pairs of unequal lengths. The stalks (filaments) are hairless. The style has an unlobed, cap-like stigma.

The fruit is a (2.6 to 3.9 mm) long, (2.6 to 3.3 mm) wide, oblong egg-shaped capsule with 100 to 200 seeds.



4¼ to 27½ (11 to 70 cm)


Flower Color

Light blue to light purplish-blue and white


Similar Species

Kalm’s lobelia (Lobelia kalmii) basal leaves are spatula-shaped. It occurs in wet areas.


Dry. Prairies, old fields, roadsides, and disturbed sites. Full sun. Sandy soil.



Mid-May to mid-June


Pests and Diseases





Distribution Map



2, 3, 4, 5, 6, 24, 28, 29, 30.






Uncommon in Minnesota



Plantae (green algae and land plants)


Viridiplantae (green plants)


Streptophyta (land plants and green algae)


Embryophyta (land plants)


Tracheophyta (vascular plants)


Spermatophytina (seed plants)


Magnoliopsida (flowering plants)




Lamiales (mints, plantains, olives, and allies)


Plantaginaceae (plantain)




Nuttallanthus (toadflax)


This species was formerly classified as Linaria canadensis. This and three other Linaria species were transferred to the new genus Nuttallanthus in 1988 based on characteristics of the flowers and the seeds.


Subordinate Taxa




Linaria canadensis


Common Names

blue toadflax

Canada toadflax

oldfield toadflax


old-field toadflax












Modified leaf at the base of a flower stalk, flower cluster, or inflorescence.



The group of outer floral leaves (sepals) below the petals, occasionally forming a tube. Plural: calyces.



Reclining on the ground but with the tip ascending.



Narrowly oval, broadest at the middle, narrower at both ends, with the ends being equal.



On plants: The thread-like stalk of a stamen which supports the anther. On Lepidoptera: One of a pair of long, thin, fleshy extensions extending from the thorax, and sometimes also from the abdomen, of a caterpillar.


Glandular hairs

Hairs spread over aerial vegetation that secrete essential oils. The oils act to protect against herbivores and pathogens or, when on a flower part, attract pollinators. The hairs have a sticky or oily feel.



Long, straight, and narrow, with more or less parallel sides, like a blade of grass.



On plants: the stalk of a single flower in a cluster of flowers. On insects: the second segment of the antennae. On Hymenoptera and Araneae: the narrow stalk connecting the thorax to the abdomen: the preferred term is petiole.



Laying flat on the ground.



An unbranched, elongated inflorescence with stalked flowers. The flowers mature from the bottom up.



A radiating group or cluster of leaves usually on or close to the ground.



An outer floral leaf, usually green but sometimes colored, at the base of a flower.



On flowers: a hollow tubular appendage, often containing nectar, formed from a sepal or petal. On branches: a short shoot bearing leaves or flowers and fruit.





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Leanne Hinke

Plants were in bloom. I have photos is you would like me to send them. There were about a half dozen plants present. This is an area that is commonly used by people in the summer, so I worry about it getting trampled.

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Nancy Falkum

blue toadflax Photos











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Other Videos

Nuttallanthus canadensis, the blue toadflax. 3 Minutes plants. Simple flower/plants movie. 3分間の植物動画
ethnobotaist isamimasi


May 6, 2020

Simple plants movie. I love watching plants movie when I do exercise or mindfulness. All movies have 3 minutes long, and you can use it as a timer for cooking, exercise , relaxation or waiting for instant noodle. Hope you enjoy it.




Visitor Sightings

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Leanne Hinke

Location: Sandy beach on the Mississippi River. Across from the power plant at Genoa. (Houston County)

Plants were in bloom. I have photos is you would like me to send them. There were about a half dozen plants present. This is an area that is commonly used by people in the summer, so I worry about it getting trampled.

blue toadflax
Nancy Falkum

Location: Kellogg Weaver Dunes SNA, Weaver Dunes Unit


blue toadflax Sightings






Created: 6/17/2022

Last Updated:

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