heart-leaved four o’clock

(Mirabilis nyctaginea)

               
Conservation Status

IUCN Red List

not listed

heart-leaved four o’clock

NatureServe

N5? - Secure

SNR - Unranked

Minnesota

not listed

Wetland
Indicator
Status

Great Plains

UPL - Obligate upland

Midwest

UPL - Obligate upland

Northcentral & Northeast

UPL - Obligate upland

Nativity

Native

 
Occurrence

 

 
Habitat

Dry. Prairies, disturbed sites. Full sun.

 
Flowering

May to August

     
Flower Color

Pink to purple

     
Height

1 to 3

     
 
Identification

This is a 1 to 3 tall, erect, perennial forb rising from a thick, dark, fleshy or woody, taproot.

The stems are hairless near the bottom and have 2 lines of fine, short hairs further upwards. They are usually erect or curve upward from the base, occasionally they recline on the ground with the tips ascending. They are forked near the top. Only the lower of the stems are leaved.

The leaves are opposite, untoothed, green, thin, and usually hairless though sometimes sparsely hairy. They are 1 to 4 long, ¾ to 2½ wide. They are egg-shaped to round lance-shaped or sometimes triangular. The bases are heart-shaped, blunt, or rounded. The tips are pointed. They are on ¼ to 1 long leaf stalks and are held ascending at a 45° to 80° angle.

The inflorescence is several branched clusters at the end of each stem branch and in the upper leaf axils. The clusters appear at the end of long, forked, hairy branches. The clusters have 3 to 5 flowers each.

The flowers are wide. They have little or no fragrance. There are 5 pink to purple petal-like sepals. The sepals are fused at the base forming a tube, then flare outward. There are 5 bracts, to ¼ long, at the base of the flower that are fused into a pale green, often tinged pinkish, saucer-shaped or broadly bell-shaped cup. The flowers open in the late afternoon, giving this plant its common name, remain open all night, and close in the morning.

The fruit is a one-seeded achene. It is subtended by the persistent, saucer-shaped fused bracts that have increased in size as the fruit developed, becoming to long.

 
Similar
Species

Hairy four o’clock (Mirabilis albida) has a hairy stem. The leaves are on shorter leaf stalks, are hairy, narrow and lance-shaped, and taper to the base. The bract cups are hairy. The flower clusters are in leaf axils, are loosely clustered on branches, or are scattered in open, widely spreading clusters, not at the end of the stems.

Narrow-leaved four o’clock (Mirabilis linearis) has linear leaves and larger flowers with much longer tubes.

 
Distribution Distribution Map   Sources: 2, 3, 4, 5, 7, 28.
 
Comments

 

 
Taxonomy

Family:

Nyctaginaceae (four o’clock)

 

Tribe:

Nyctagineae

 
Synonyms

Allionia nyctaginea

Mirabilis collina

Oxybaphus nyctagineus

 
Common
Names

heartleaf four o’clock

heartleaf four-o’clock

heart-leaf four-o’clock

heart-leaf umbrella-wort

heart-leaved four o’clock

heart-leaved umbrella-wort

pale umbrella-wort

prairie four o’clock

white four-o’clock

wild four oclock

wild four-o’clock

umbrella-wort

 

 

 

 

 

 

 

 

Glossary

Achene

A dry, one-chambered, single-seeded fruit, formed from a single carpel, with the seed attached to the membranous outer layer (wall) only by the seed stalk; the wall, formed entirely from the wall of the superior ovary, does not split open at maturity, but relies on decay or predation to release the contents.

 

Axil

The upper angle where the leaf stalk meets the stem.

 

Bracts

Modified leaves at the base of a flower stalk or flower cluster.

 

Linear

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

 

Sepal

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

       
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Plant

  heart-leaved four o’clock   heart-leaved four o’clock
       
  heart-leaved four o’clock   heart-leaved four o’clock
       

Inflorescence

  heart-leaved four o’clock   heart-leaved four o’clock
       
  heart-leaved four o’clock   heart-leaved four o’clock
       

Flowers

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Leaves

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  heart-leaved four o’clock    
       

Stem

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Infructescence

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Fruiting Head

  heart-leaved four o’clock   heart-leaved four o’clock
       
  heart-leaved four o’clock   heart-leaved four o’clock
       

Early Spring

  heart-leaved four o’clock   heart-leaved four o’clock
       
  heart-leaved four o’clock    
       
       

 

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