Nuttallanthus canadensis (Old-field Toadflax)
|Also known as:||Blue Toadflax, Canada Toadflax|
|Life cycle:||annual, biennial|
|Habitat:||sun; dry sandy soil, prairies, roadsides|
|Bloom season:||May - July|
|Plant height:||4 to 20 inches|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Flowers are in a spike-like raceme at the top of the stem that elongates up to 8 inches. Individual flowers average about 1/3 inch long, irregular with an upper lip divided into 2 erect rounded lobes, and a lower lip with 3 rounded lobes. Flower color is blue to blue-violet, with a 2-humped white spot at the base of the lower lip. There is usually 1 spike on a stem, but a plant may have multiple stems.
Leaves and stem:
Leaves are 1 to 1½ inches long and very narrow—not more than 1/8 inch wide, toothless, hairless, with pointed tips and no leaf stalk. They are alternately attached and narrower on flowering stems, but oppositely attached and broader on the shorter non-flowering stems. The main stem is smooth and slender, green to reddish brown.
Fruit is a small, rounded capsule containing many tiny seeds.
Old-field Toadflax, formerly Linaria canadensis, is an uncommon species in Minnesota, where it reaches the northwest limit of its range. According to the DNR, it has only been documented about 25 times in the state, primarily in sparsely vegetated, sandy soils that have been recently disturbed, such as pocket gopher mounds or even plowed fields. I encountered it one year in a sandy horse trail at Wild River State Park but it disappeared in subsequent years. Commercial development, agriculture and invasive species have all contributed to either destruction or degradation of suitable habitat and it was listed as a Special Concern species in 2013. With its small flowers and foliage and slender stems, this may be easy to miss unless there is a clump of plants together. It superficially resembles Kalm's Lobelia (Lobelia kalmii), which has spoon-shaped basal leaves and is found it moister habitats.
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Photos by K. Chayka taken at Wild River State Park, Chisago County. Photos by Peter M. Dziuk taken in Sherburne National Wildlife Refuge.
Have you seen this plant in Minnesota, or have any other comments about it?