The notulae series functions as a formal ledger for Italy’s alien vascular flora, the country’s standard reference for tracking non-native plant distribution. Each entry is a short, georeferenced note submitted by field botanists, accompanied by a voucher specimen deposited in a public herbarium, most often the FI Herbarium at the Museo di Storia Naturale in Florence. The system distinguishes between casual aliens, which persist only through repeated introduction, naturalized aliens, which reproduce without human help, and invasive aliens, which spread aggressively and threaten native communities. The 2025 update moves several taxa up that ladder, including two species newly recognized as invasive for Italy as a whole, and it adds regional firsts for Valle d’Aosta, Lombardia, Trentino-Alto Adige, Marche, Lazio, Puglia, Calabria, Sardegna, Umbria, Sicilia and Campania.

The most consequential single entry concerns Hydrocotyle verticillata, a perennial aquatic plant native to the Americas and sub-Saharan Africa, which is now formally recorded as an invasive alien new for the flora of Italy. Field surveys at Lake Bracciano, a volcanic lake northwest of Rome, first collected the species in September 2024 on the southern shore. By the summer of 2025, botanists had documented it at numerous sites around the entire lake, from Bracciano town to Trevignano Romano, where it thrives in managed lawns of beach clubs and at the water-land interface. Researchers identified the species using the dichotomous key in Schou et al. (2023) and note that it co-occurs with Ludwigia hexapetala, another aggressive aquatic alien, colonizing the front zones of helophyte communities. The expansion directly threatens native vegetation characteristic of habitat type 3130, the oligotrophic to mesotrophic standing waters with Littorelletea and Isoëto-Nanojuncetea communities protected under the European Habitats Directive.

A second species newly upgraded to invasive status for Italy is Freesia leichtlinii subsp. alba, a South African iris cultivated for its eye-catching white flowers. On the island of Sardegna, botanists found a diffuse population with thousands of flowering individuals in the municipality of La Maddalena, and a similar situation near Castiadas, where hundreds of plants have colonized the undergrowth of coastal pinewoods. Along the western coast, from Marina di Arborea to S’Ena Arrubia in the province of Oristano, the species is currently invading several sites. In Cagliari, on the hill of Sant’Elia near Calamosca, it spreads along paths, likely originating from abandoned garden remnants. The upgrade moves the taxon from naturalized to invasive for Italy and from casual to invasive for Sardegna, confirming that ornamental trade pathways can produce fully autonomous invaders in Mediterranean climates.

The aquatic genus Myriophyllum adds another chapter to the same story. Myriophyllum aquaticum, a perennial hydrophyte native to South America and introduced for ornamental purposes, is listed among the invasive alien species of Union concern under Regulation (EU) n. 1143/2014, meaning member states are obliged to manage it. In Sardegna, researchers documented two stands: one in a stretch of the Flumineddu stream near Serdiana, forming a dense population extending over a few dozen meters, and another near Arzachena in a shallow water body. The Sardinian regional environment department informed the authors of an iNaturalist record from 2018, and an inspection confirmed the plant’s persistence. The individuals observed are female plants, probably originating from commercially introduced aquarium and pond stock accidentally discarded into natural habitats, a pathway botanists flag as recurring across the archipelago.

Cacti feature prominently in the update, reflecting the growing footprint of the ornamental succulent trade in Italy’s warm regions. Cylindropuntia imbricata subsp. spinosior is newly recorded as naturalized for Trentino-Alto Adige, found on an inaccessible rocky scarpata within a gorge on the Passirio river near Merano, in association with Opuntia engelmannii and O. humifusa. Opuntia lindheimeri moves from casual to naturalized in Umbria, where a population near Spello had been previously misidentified from a depaupered herbarium exsiccatum lacking reproductive elements. Opuntia microdasys is newly naturalized for Calabria, observed on the steep slopes of the promontory linking Badolato to the ancient Chiesa dell’Immacolata, where detached pads fracture off, tumble downslope and establish new stable clusters through asexual propagation.

Several other species complete their naturalization in specific regions for the first time. Ceratochloa cathartica, a South American grass, moves from casual to naturalized in Valle d’Aosta, where numerous populations between Montjovet and Bard support complete establishment. Chamaeiris orientalis, an eastern Mediterranean iris, achieves naturalization in Lombardia after several years of observation, with a lush population in full bloom occupying roughly 10 square meters on a torrent bank at Sesto Calende. Cyperus esculentus, the yellow nutsedge, is newly naturalized for Marche, found on embryonal dunes at Falconara Marittima with several dozen individuals scattered across a psammophilous grassland dominated by Thinopyrum junceum. Euphorbia lathyris moves from casual to naturalized in Lazio, where a dense population of more than 150 individuals over about 400 square meters at Torrita Tiberina now reproduces without human intervention, perhaps having been initially cultivated as ornamental.

The update also documents the naturalization of trees and shrubs with significant ecological implications. Lagunaria patersonia, an Australian Malvaceae, moves from casual to naturalized for Italy and is newly naturalized for Puglia, with two mature fruiting specimens found in the heart of the San Cataldo Biogenetic Nature Reserve near Vernole, one approximately 8 meters tall and the other 4 meters tall, plus a seedling about 20 meters away. Schinus terebinthifolia, the Brazilian pepper tree, moves from casual to naturalized in Sardegna, where abundantly fruiting shrubs up to 3 to 4 meters tall thrive along the edges of the San Teodoro pond, having escaped from road trees planted along the street leading to La Cinta Beach. Researchers note abundant seedlings and warn that, given the species’ demonstrated invasiveness in Florida’s Everglades, containment interventions should be made before its expansion becomes unmanageable.

Grasses and herbaceous ornamentals round out the regional firsts. Megathyrsus maximus var. pubiglumis, a tropical grass, is newly naturalized for Calabria, with self-replacing populations at Scilla near the Castello Ruffo, where its phenology concentrates during the temperate rainiest months. Sporobolus indicus is newly naturalized for Valle d’Aosta, found in roadside flowerbeds at Pont-Saint-Martin and in pavement cracks at Donnas, with vehicle transit from Piemonte flagged as the probable introduction vector. Sparaxis tricolor and Talinum paniculatum both move from casual to naturalized in Sardegna, with the Sparaxis population at San Teodoro confirming an earlier record at Gonnesa and a nearly 30-year-old garden planting at Berchidda demonstrating the species’ capacity to colonize and escape. Tradescantia pallida achieves naturalization in Sicilia, observed in sidewalk interstices across numerous Palermo streets, and Glinus lotoides is newly naturalized for Puglia, found in a periodically submerged grazed grassland at Gravina in Puglia.

Not every entry adds a species. Bidens radiata is formally excluded from the flora of Campania after a review of the relevant herbarium specimen by A. Croce revealed that the sole regional record, from Roccamonfina in 2008, actually belongs to B. frondosa. The correction underscores the role of herbarium vouchers in maintaining the accuracy of the national alien flora ledger, since misidentified specimens can propagate errors through decades of literature. Nomenclatural and distribution updates published elsewhere, along with corrections to the 2024 national checklist, are provided in the supplementary material. The working group continues to accept new records, status changes and exclusions electronically, with vouchers deposited at the FI Herbarium in Florence, ensuring that the rolling census of Italy’s alien vascular flora remains a living document rather than a static snapshot.

Subject of Research: Distribution updates of alien vascular plant taxa in Italy, including new records, status changes and exclusions

Article Title: Notulae to the Italian alien vascular flora: 20

Article References: Galasso, G., Domina, G., Ardenghi, N. M. G., Argenti, E., Azzella, M. M., Bacchetta, G., Bajona, E., Barone, G., Bartolucci, F., Bertotto, G., Bonivento, E., Brundu, G., Calvia, G., Camilletti, M., Costanzo, E., Croce, A., Cuena-Lombraña, A., Del Guacchio, E., Di Gristina, E., … Lastrucci, L. (2025). Notulae to the Italian alien vascular flora: 20. Italian Botanist, 20, 109-124. https://doi.org/10.3897/italianbotanist.20.179465

Image Credits: AI Generated

DOI: 10.3897/italianbotanist.20.179465

Keywords: Notulae, Italian, alien, vascular, flora, scientific research