We continue the series of detailed treatments of alien vascular plants of Kyrgyzstan. The complete background for every species occurrence (herbarium specimens, documented observations, published literature) is uncovered and critically evaluated in a wide context of plant invasions in Central Asia with a reference to Eastern Europe and Northern Asia, based on events in the political and economic history. Complete point distribution maps are provided for each species in Central Asia, in general and Kyrgyzstan, in particular.

All records of Hesperis matronalis in Central Asia (including Kyrgyzstan) belong to H. pycnotricha; the latter species is newly reported as a locally naturalised alien in Kazakhstan. The previous record of Sisymbrium irio from Kyrgyzstan is rejected as based on a misidentified specimen of S. loeselii, but the species is newly recorded here as a recent casual alien. Hirschfeldia incana is presumably native in south-western Turkmenistan; its second record in Central Asia was caused by the import of contaminated wheat grain in the times of the Soviet grain crisis and its recent expansion may be linked to the increasing import of forage grain. The introduction of Crambe orientalis was connected with its cultivation for fodder and as an ornamental plant and its further broad dispersal was aided by winds. Rorippa austriaca is native in the steppes of north-western Kazakhstan, but alien in the mountains of Central Asia. The occurrences of three alien species originated directly from cultivation (Hesperis pycnotricha as an ornamental, Armoracia rusticana as an edible plant, Crambe orientalis as an ornamental and fodder plant), three species (Hirschfeldia incana, Mutarda arvensis, Sisymbrium irio) were imported as grain contaminants, whereas two others (Rorippa austriaca, R. sylvestris) have arrived with contaminated soil on ornamental plants or arboreous saplings. The arrival period is inferred as the Neolithic period (Mutarda arvensis), the Imperial times (Armoracia rusticana, Hesperis pycnotricha), the post-war Soviet times (Crambe orientalis, Rorippa austriaca, R. sylvestris) and the independence times (Hirschfeldia incana, Sisymbrium irio). All the treated species, but two, increase their frequency in Kyrgyzstan; Mutarda arvensis has already reached its complete distribution, being an ubiquitous weed, whereas Armoracia rusticana experiences a projected decline because its common cultivation has ceased. No species is invasive in natural habitats. A new combination, Mutarda arvensis var. orientalis (L.) Sennikov, is proposed for a variant with pubescent pods.