''Flora of the city of Zurich'' includes 350 monocot species. 28 of th
ese are frequent ergasiophytes and ephemerophytes which scarcely sprea
d within the area. Only about half of the remaining 322 species are no
t endangered, 45 (14%) are extinct (Ex), 69 (21%) endangered (E), and
48 (15%) vulnerable (V). Five systematic groups may be distinguished i
n respect to their dynamics: A) families with predominantly water and
fen plants; B) Cyperaceae and Juncaceae; C) Gramineae (Poaceae); D) Li
liaceae, Amaryllidaceae, Iridaceae, Dioscoreaceae; E) Orchidaceae. The
group D is characterized by the highest percentage of neophytes (37%)
, the highest percentage of species increasing in frequency (50%), the
lowest percentage of endangered as well as vulnerable and extinct spe
cies (18% and 10%, respectively), and the highest degree of urbanity.
On the other hand, neither neophytes nor species increasing in frequen
cy are represented in group E. However, 22% of the species of this gro
up are extinct and 52% vulnerable or endangered. The degree of urbanit
y of the species is very low. It is important to the conservation and
promotion of the endangered plants to protect the few remaining areas
with a high species diversity (Uetliberg, Katzensee, Wehrenbachtobel).
On the other hand, many smaller less spectacular areas containing rar
e species should also be preserved. Open sites, e.g., gravel places, n
ot-sealed parking lots and industrial areas, road sides, stone walls,
railway escarpments are, too, favourable compensatory sites for weeds
and pioneer plants.