Lythrum salicaria L. - Swamp Loosestrife

Lythrum salicaria plant

Family - Lythraceae

Stems - Multiple from base, becoming woody at the base, herbaceous above, to 2m tall, 4-angled, scabrous, pubescent to hispidulous, erect.

Lythrum salicaria stem

Leaves - Opposite to subopposite in inflorescence, linear-lanceolate to oblong-linear, sessile, somewhat clasping or not, entire, scabrous, +/-10cm long, +/-2cm broad, acute, reduced upward, greatly reduced in inflorescence to foliaceous bracts.

Lythrum salicaria leaves

Inflorescence - Dense terminal spikes with clusters of 3-9 flowers per node. Flowers subtended by reduced leaf(foliaceous bract). Bracts dense pubescent. Axis of inflorescence dense pubescent to tomentose.

Flowers - Petals 5, borne at apex of floral tube, to 7mm long, 3.5mm broad, glabrous, subequal, oblong-obovate, pinkish-rose. Stamens 10-12, in two sets of five or six each. Longer set of stamens well exserted. Filaments to 1.3cm long, adnate at base of floral tube. Anthers purple. Shorter set of stamens included to slightly exserted. Filaments white and fading to pinkish-purple at apex. Anthers yellow. Ovary cylindrical-conic, 2.5mm long, 1mm in diameter, glabrous. Style 1mm long, curved. Stigma glandular, capitate, green. Floral tube to 7mm long, 3mm in diameter, cylindric, 12-nerved, dense pubescent, with 6 appendages. Appendages linear-attenuate, 2-3mm long, greenish, alternating with calyx lobes. Calyx lobes pink, to 1mm long, shorter than appendages, acute.

Lythrum salicaria flowersFlower close-up.

Lythrum salicaria calyxCalyx.

Flowering - June - September.

Habitat - Moist to wet ground along ditches, streambanks, meadows, waste ground, prairies, roadsides, railroads. Also cultivated.

Origin - Native to Europe.

Other info. - Efforts to keep this plant under control in Missouri so far have met with moderate success. The plant is rare in the wild and typically gets destroyed upon its discovery. You can help too. If you find the plant in the wild, report its location to Missouri Department of Conservation. This is no laughing matter as anyone who has been to New England or the Northeast can attest. The plant is highly invasive and can quickly spread through an area and out-compete all native flora. It creates a sea of pink which may be pretty to look at but is an environmental disaster. Don't be tempted to grow it at home, find something else.

Photographs taken off Hwy 64, somewhere in the U.P. of Michigan, 9-7-03.


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