In considering the question of non-indigenous plants, the propensity of a
species to spread into the wild is important.
A few years ago Emeritus Professor Stone (Botany, University of Melbourne)
sought my help in locating an area in suburban Brisbane which was the type
locality for a species of moss in the group she was reviewing for the
Australian Flora. No trouble to find the area (Council parkland along a
creek) but it is now a pure stand of Chinese Elm (Celtis sinensis). Native
flora has largely disappeared. We did not find the moss.
This elm is a common weed in our (Hawthorne, Brisbane) garden.
I occasionally see feral peach trees in the bush and it seems to me that
where a seed discarded beside a road germinates and survives, eventually
producing peaches, more peach plants will arise as animals distribute the
seeds. But it spreads very slowly. The fruits are never carried very far,
and very few actually succeed in germinating and surviving. Possibly a
similar low success rate applies to Elm seeds, but they are myriad compared
to peach stones and they are carried far and wide by birds.
I have not noticed cabbages or apple trees become feral.
Syd
H Syd Curtis
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