Annual or perennial herbs, sometimes shrubs, rarely trees. Leaves opposite, less often whorled or rarely alternate, simple, mostly entire; stipules absent or small, commonly appearing as a row of minute hairs. Flower clusters in spikes or branched clusters, sometimes solitary. Inflorescence various, a racemose spike, cymose panicle or a solitary, axillary flower. Flowers bisexual, regular or irregular, 4, 6 or 8-parted with a prominent hypanthium that sometimes has an epicalyx or spur, hypanthium commonly ribbed. Sepals edge to edge in bud; tooth-like appendages sometimes present between sepals. Petals free or absent, usually 4–6, free, crumpled in bud and wrinkled at maturity. Stamens (–4)8–16(–numerous) mostly twice the number of sepals or petals, mostly in 2 whorls, usually attached well to slightly below the apex of the hypanthium, filaments of unequal length, sometimes with a nectar disk below, anthers dehiscing by longitudinal slits. Ovary superior or rarely inferior, of 2–6(–numerous) united carpels with axile placentation, rarely free-central or parietal; stigma more or less capitate; heterostyly common. Ovules 2 to numerous in each locule. Fruit a dehiscent or indehiscent capsule containing numerous seeds, occasionally berry-like; seeds usually flattened and or winged.
Heimia salicifolia (HBK) Link from S America is a shrub that is occasionally cultivated; it has linear-lanceolate leaves to about 7 cm long and yellow flowers with petals about 2 cm long. Lythrum salicaria L., Purple Loosestrife, a cosmopolitan species is a herbaceous perennial that is present in moist parts of SA, Qld, Vic and Tas., but is of uncertain origin status. L. virgatum L. from N America is similar and has weed potential; it has leaves that are narrowed, not cordate, at the base and it is available as the cultivar, 'Rose Queen', which has clear deep violet-pink flowers.
Several species are sources of dyes, including the orange dye, henna, which is extracted from the leaves of Lawsonia inermis. Red and yellow dyes are extracted from tropical genera such as Lafoensia. Lagerstroemia and Physocalymma have attractively coloured wood. Hallucinogenic drugs are extracted from some species of Heimia (rarely cultivated) and Lagerstroemia. Punica granatum L. is grown for the attractive flowers and edible fruit.
Opposite, usually entire leaves; hypanthium commonly ribbed, epicalyx commonly present; flowers with 4–6 petals and sepals; stamens twice as many as sepals and petals, the petals often crinkled with a narrow claw and borne on a large calyx tube with the stamens attached at different levels.
31 genera with about 650 species, mostly tropical but a few temperate species; 8 genera and c. 24 species in Australia.
Now includes Puniaceae, Sonneratiaceae and Trapaceae. This treatment follows Stevens, P.F. (2018, Angiosperm Phylogeny Website).
Source: (2002). Lythraceae. In: . Horticultural Flora of South-eastern Australia. Volume 3. Flowering plants. Dicotyledons. Part 2. The identification of garden and cultivated plants. University of New South Wales Press.
Updated by: Val Stajsic, March 2018