Hydrolea uniflora Raf.

One-flowered Hydrolea

Hydrolea uniflora plant

Family - Hydroleaceae

Stem - To 1 m long, prostrate with erect or ascending branches, glabrous or finely pubescent. Thorns often present, singly or paired, in leaf axils.

Hydrolea_uniflora_stemStem and thorn.

Leaf - Simple, sessile or short petioled, lanceolate, to 10 cm long, entire, glabrous or finely pubescent.

Hydrolea_uniflora_leafLeaf adaxial.

Hydrolea_uniflora_leaf2Leaf abaxial.

Inflorescence - Axillary clusters.



Flowers - Actinomorphic, hypogynous, perfect. Calyces deeply 5-lobed, lobes 5-8 mm, ovate, glabrous or finely pubescent, occasionally with sparse, sessile glands. Corollas deeply 5-lobed, 7-11 mm long, lobes broadly elliptic and rounded at tips, blue. Stamens 5, filaments broadened at base and adnate to base of corolla. Pistil 1, of 2 fused carpels.


Fruits - Globose capsules, longitudinally dehiscent, glabrous. Seeds numerous.

Hydrolea_uniflora_fruitsImmature fruits.

Flowering - June - September.

Habitat - Swamps, sloughs, wet ditches.

Origin - Native to the U.S.

Other info. - This attractive but uncommon species is restricted to the Mississippi Lowlands division, which is the northern extent of its natural range. The plant is always a welcome find, though it must be handled with care (if at all) due to the sharp thorns which are often present.
In the past, Hydrolea has been included within the Hydrophyllaceae.

Photographs taken at Otter Slough Conservation Area, Stoddard County, MO, 8-13-2015 (SRTurner).