Biological invasions have become a major concern in the past decades. It is generally accepted that an early detection of new alien species is essential because lag-phases (‘invasion debt’) are on average 20–30 years, meaning that today’s rare but fast spreading aliens may become tomorrow’s noxious weeds. In the past years it has become evident that an increasing number of non‐native vascular plants have become naturalized or even invasive without ever being noticed. A well suited approach for early detection of non-native species, even if these do not exhibit the diagnostic features required for determination, is DNA barcoding. This PhD project is focusing on ultrabarcoding of species from the genera Chenopodium s.l. from the Amaranthaceae and Eragrostis and Panicum from the Poaceae to gain information about cryptic invasive species (‘invaders in disguise’) in Austria. For that purpose, NGS techniques (“genome skimming“ with and without a PCR step) are applied to sequence complete plastid genomes and nuclear ribosomal DNA. The method with a PCR step is functioning well even with historical herbarium vouchers (“herbarium genomics”). It will be tested (i) if ‘invaders in disguise’ can be detected with standard DNA barcoding techniques, (ii) if DNA barcoding can help quantifying invasion debts of potentially invasive species in Austria; and (iii) if traditional alpha taxonomy in combination with DNA barcoding can improve accuracy of species identification and further refine taxonomic classification of cryptic invasive plant species. This project will be of relevance in developing management and monitoring strategies for invasive plants.