Houstonia longifolia (Long-leaf Bluets)

Plant Info
Also known as: Long-leaf Houstonia, Long-leaf Summer Bluet
Family:Rubiaceae (Madder)
Life cycle:perennial
Habitat:part shade, sun; moist to dry rocky or sandy soil; prairies, savannas, open woods, rock outcrops
Bloom season:June - August
Plant height:3 to 10 inches
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 4-petals Flower shape: tubular Cluster type: flat Cluster type: panicle

[photo of flowers] Flowers are clustered in 2s or 3s at the ends of branching stems in the upper part of the plant. Individual flowers are about ¼ inch across, white to pale blue or occasionally pink, tubular with 4 sharply pointed lobes and 4 stamens with creamy white to yellow tips that turn blackish with age. The inside of the floral tube is hairy. The calyx cupping the flower is much shorter than the floral tube and has 4 narrowly triangular lobes. Flower buds are often pink.

Leaves and stem: Leaf attachment: basal Leaf attachment: opposite Leaf type: simple

[photo of leaves] Basal leaves may be present but typically wither by flowering time. Stem leaves are narrow, to 1¼ inches long and ¼ inch wide, toothless and hairless, stalkless with a pointed tip. Attachment is opposite and there is a small whitish triangular appendage (stipule) on opposite sides the leaf node. Stems are 4 sided with rounded corners, mostly smooth except sometimes minutely hairy along the angles, especially on the lower stem, and either branched or unbranched except in the flower clusters.

Fruit: Fruit type: capsule/pod

[photo of fruit] Fruit is a 2-sectioned capsule, each section more or less round.


Long-leaf Bluets are easily recognized by its tiny, 4-petaled flowers that are white to pink to pale blue, its square stems and opposite, oblong-linear leaves with triangular stipules. Its taxonomy has switched back and forth between Hedyotis longifolia and Houstonia longifolia with the latter being the currently recognized name.

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More photos

Photos by K. Chayka taken at Wild River and Interstate State Parks, Chisago County. Photos by Peter M. Dziuk taken in Chisago and Redwood counties. Houstonia longifolia (fruit) by Keir Morse used under CC BY-NC-SA 3.0.


Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Sue - Interstate State Park, Taylors Falls side
on: 2011-03-13 17:55:02

I saw these last summer while photographing the area.

Posted by: Carole - Wild River State Park, Center City MN
on: 2012-08-19 16:08:49

Saw some of these blooming today, Aug 19, 2012 at wild river. Saw what looked like blue-eyed grass in August, did a double take and went to check them out! What a sweet little flower!

Posted by: Jodi - Minnehaha Falls
on: 2013-08-25 16:43:08

These are blooming all over on the lower paths by the falls.

Posted by: Joe Lindgren - Jay Cooke State Park
on: 2018-06-16 15:14:50

A lovely cluster of these in full bloom in a rocky outcropping near the St. Louis River.

Posted by: Joelle - Louisville Swamp Unit Minnesota Valley NWR
on: 2020-05-30 15:23:42

Don't recall seeing these before so I took a photo on my walk today.

Posted by: Timothy Johnson - Crow Hassan Park Preserve
on: 2021-05-30 11:29:01

When I searched your advanced plant search with the following, bluets did not come up. Shouldn't my criteria have shown them?
Criteria: type=flower; flower=white,4-petals; leaves=opposite,simple,toothless;

Posted by: K. Chayka
on: 2021-05-30 17:45:56

Timothy, I see bluets in those results, #12 of 13.

Posted by: Steve Poole - River Terrace Prairie SNA
on: 2022-06-08 18:40:43

A lot of these plants are blooming right now. They are located on the north facing slope of the river terrace. The slope is rocky gravely and sandy with very thin vegetation. Clusters of flowers occur with just a few flowers or a dozen or more.

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