- Name also: Tatarian Catchfly, Tartar Catchfly, Tatar Catchfly
- Family: Pink Family – Caryophyllaceae
- Growing form: Perennial herb.
- Height: 30–50 cm (12–20 in.). Many-stemmed, stem at least at base sparsely hairy, upper part glabrous.
- Flower: Corolla regular (actinomorphic)–slightly zygomorphic, white (often greenish or yellowish), approx. 2 cm (0.8 in.) wide; petals 5, deeply 2-lobed. Without corona. Calyx fused, narrow, 5-lobed, clearly 10-veined, glabrous. Stamens 10. Pistil of 3 fused carpels, styles 3. Inflorescence a long, narrow, many-flowered, sparse, often one-sided raceme.
- Leaves: Opposite, stalkless, stem leaves 6–10 pairs, lowest small and withering early. Blade elongatedly ovate–linear, with entire margins, base sparsely ciliate.
- Fruit: Cylindrical, 8–10 mm (0.32–0.4 in.) long capsule.
- Habitat: River banks, sandbanks, estuary sea shores, sand fields, roadsides, railway embankments, loading areas.
- Flowering time: July–August.
- Endangerment: Near threatened.
Tartarian catchfly is not as eastern as its name implies: its heartland is in eastern Europe but it has never spread as far as Asia. It has arrived in Finland however from the east during the late Ice Age or soon after, when Finland was mainly windy steppe. It has perhaps grown quite commonly then on the wide grasslands, which later gave way to coniferous forest. Tartarian catchfly has endured as a legacy of a more continental climate only along northern riversides. Its current habitats are in Kuusamo and Lapland on the banks of the River Oulunka and River Kemi respectively, along with different kinds of stands scattered here and there in northern Finland. Spring floods sweep away river banks, keep vegetation open and create new growing places. This kind of restless atmosphere is actually a sanctuary for Tartarian catchfly and other plants that shun vigorous competition and need room to grow. Tartarian catchfly disappeared from the banks of peaceful and frequently travelled rivers millenia ago. Regulation of the water flow is a threat to stands that have remained: some of them have ended up under reservoirs, while some have disappeared from banks as a lack of flooding has led to excess growth.
Tartarian catchfly is pollinated by insects and makes an abundance of seeds, which spread on the water and possibly also with animals and even vehicles. Outside northern Finland the plant is a travelling alien which has even been found in Santahamina in Helsinki in the southern coast of Finland, hundreds of kilometres from the nearest stand. It is worth looking for it along roadsides, in railway yards and in loading areas. These mimic the same conditions of its original habitats on steppes and steppe forest margins: space to grow and light and heat in abundance, sparse nutrition, occasionally very dry and susceptible to winter cold.