The present paper provides an overview of all naturalized vascular plants in Flanders (Belgium) with emphasis on taxa naturalized after 1945. Besides, a checklist is presented, enumerating all non-native taxa (exl. archeophytes) recorded since 1972.
All non-indigenous vascular plants were taken into account. In practice, the delimitation native/non-native sometimes turned out to be difficult. Arguments for inclusion or exclusion are dealt with in detail.
The degree of naturalization of a given taxon is indicated using a manageable set of five definitions (following several other recent researchers): planted, ephemerous, persistent, naturalized or invasive. The selected status of each taxon is based on a revision of several herbaria, a revision of relevant literature, field check-up and data extracted from the Florabank database (= database with all floristic data from Flanders).
Nowadays, gardens and plantations proved to produce the largest amounts of non-indigenous taxa in Flanders. Moreover, most of the taxa with tendencies towards invasiveness are also garden-escapes (recently especially hydrophytes).
The major part of this paper consists of taxonomic enumeration (pteridophytes and spermatophytes, in alphabetical order according to family and genus) of those taxa believed to be naturalized after 1945. For every taxon the following data-set is dealt with:
1. Actual distribution, ,distribution ecology and trends;
2. Origin and vector of distribution
3. Ecology, competition and (potential) invasiveness.
An up-to-date distribution map for Flanders is provided if relevant (for instance if the taxon’s distribution pattern has changed considerably since the publication of the latest Belgian distribution atlas; Van Rompaey & Delvosalle 1978, 1979). Furthermore, a commented list is presented with taxa considered to be "persistent" and with taxa which are doubtfully naturalized.
Finally, a list with taxa already naturalized before 1945 is given.
In addition a checklist of vascular non-native (1972-2001) plants, excl. archeophytes, is provided. For each taxon the following data are presented: family, reference of the data, status (degree of naturalization), area of origin, mean of introduction, time of introduction and (exclusively for naturalized taxa) ecological data. Separately a list with doubtful taxa (identification and/or presence in Flanders need confirmation) is also presented.