long-leaved bluet

(Houstonia longifolia)

Conservation Status
long-leaved bluet
  IUCN Red List

not listed

     
  NatureServe

NNR - Unranked

SNR - Unranked

     
  Minnesota

not listed

     
           
           
 
Description
 
 

Long-leaved bluet is a more-or-less erect, perennial forb that rises on a rosette of basal leaves and few to several stems from a perennial base; slender, sometimes thread-like, underground stems (rhizomes); and fibrous roots.

The stems erect or ascending, slender to rather stout, much branched, and 2 to 11¾ long. They have between 3 and 13 internodes. The distances between the lower stem nodes (internodes) are usually not conspicuously longer than the upper ones. The stems may be entirely hairless or minutely hairy, especially at the nodes.

Basal leaves are on leaf stalks (petioles) that are shorter than or rarely longer than the blades. The petioles and blades together are from 3 16to 1½ long and up to wide. The blades are elliptic to inversely lance-shaped. They are narrowly angled or tapered at the base and bluntly pointed or rounded at the tip. The margins are untoothed and flat or slightly rolled under, and may have a minute fringe of hairs visible only with magnification (0.1 to 0.2 mm). The upper surface is hairless or sparsely short-hairy. The lower surface is hairless.

Stem leaves are unstalked or short-stalked, linear to narrowly oblong, no more than ¼ wide, and bluntly pointed at the tip. They are otherwise similar to basal leaves. They have a single midvein and no visible lateral veins, even on the wider leaves. At the base of each leaf there is a triangular to egg-shaped, about long, leaf-like structure (stipule).

The inflorescence is one to several flat clusters of 2 to 7 flowers at the end of the stem and sometimes also from the upper leaf axils. Each flower is on a 1 16 to 5 16long stalk (pedicel).

The flowers are funnel-shaped and about ¼ across. They have 4 sepals, 4 petals, 4 stamens, and 1 style with 2 stigmas. The sepals are green and are united into a calyx tube with 4 spreading, narrowly triangular, 1 32 to long lobes. They are no more than ½ as long as the corolla tube. The petals are united at the base into a to 3 16 long corolla tube then separated into 4 spreading, triangular, 1 16 to long lobes. They are white to purple or pinkish-purple, or sometimes bluish. They do not have a yellow or reddish ring of at the top of the throat. They are hairless outside, hairy in the tube and on the inner (top) surface of the lobes. In a strategy to promote cross-pollination, two types of flowers are produced, known as pin and thrum flowers. They are identical except for the placement and length of the stamens and styles. Pin flowers have the anthers within the corolla tube and the style projecting beyond the throat. Thrum flowers have the style within the corolla tube and the anthers at the throat or projecting just beyond it.

The fruit is 2-lobed capsule with several seeds. The capsule is globe-shaped to egg-shaped, 1 16 to long, and 1 16 to wide. It is not flattened or is only slightly flattened. When ripe, it splits longitudinally from the tip, dispersing the seeds.

 
     
 

Height

 
 

3 to 10

 
     
 

Flower Color

 
 

Bluish-purple to white

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

Moderately moist to dry. Prairies, upland woodland openings. Full or partial sun. Sandy or gravelly soil.

 
     
 
Biology
 
 

Flowering

 
 

June to August

 
     
 
Use
 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

2, 3, 4, 5, 7, 28, 29, 30.

 
  6/29/2017      
         
 

Nativity

 
 

Native

 
         
 

Occurrence

 
 

Common

 
         
 
Taxonomy
 
  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Magnoliopsida (dicots)  
  Superorder Asteranae  
 

Order

Gentianales (gentians, dogbanes, madders, and allies)  
 

Family

Rubiaceae (madder)  
  Subfamily Rubioideae  
  Tribe Spermacoceae  
 

Genus

Houstonia (flowering bluets)  
       
 

Plants in the genus Houstonia were formerly placed in the genus Hedyotis. The latter was a “dust-bin” genus, containing many distinct groups of species that did not fit comfortably into other defined genera. The segregated genus Houstonia contains 20 species native to North America with seeds having ventral cavities or depressions (crateriform); having chromosome numbers of 6, 7, 8, and 11; and by pollen type.

 
       
 

Subordinate Taxa

 
 

Some authors recognize two varieties, var. longifolia and var. tenuifolia, based on the length of the pedicels and the width of the leaves. A recent analysis of the species across its entire range (Terrell, 1996) does not support the split. When plants first begin to flower the pedicels are short, but they expand as the flowering continues.

 
       
 

Synonyms

 
 

Hedyotis longifolia

Hedyotis longifolia var. tenuifolia

Hedyotis nuttalliana

Hedyotis purpurea var. longifolia

Hedyotis purpurea var. tenuifolia

Houstonia longifolia var. compacta

Houstonia longifolia var. glabra

Houstonia longifolia var. tenuifolia

Houstonia purpurea var. tenuifolia

Houstonia tenuifolia

Oldenlandia purpurea var. tenuifolia

 
       
 

Common Names

 
 

bluet

long-leaf summer bluet

long-leaved houstonia

longleaf bluet

longleaf summer bluet

slender-leaved bluets

 
       

 

 

 

 

 

Glossary

Axil

The upper angle where a branch, stem, leaf stalk, or vein diverges.

 

Calyx

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

 

Corolla

A collective name for all of the petals of a flower.

 

Internode

The portion of a stem between nodes.

 

Linear

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

 

Node

The small swelling of the stem from which one or more leaves, branches, or buds originate.

 

Pedicel

In plants: the stalk of a single flower in a cluster of flowers. In Hymenoptera and Araneae: the narrow stalk connecting the thorax to the abdomen.

 

Petiole

The stalk of a leaf blade or compound leaf that attaches the leaf blade to the stem.

 

Rhizome

A horizontal, usually underground stem. It serves as a reproductive structure, producing roots below and shoots above at the nodes.

 

Sepal

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

 

Stipule

A small, leaf-like, scale-like, glandular, or rarely spiny appendage found at the base of a leaf stalk, usually occurring in pairs and usually dropping soon.

 

 

       
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