1. Non-native Plants A London Perspective Mark Spencer
Senior Curator, British and Irish Herbarium, Natural History Museum
BSBI vc 21 (Middlesex) Recorder
LNHS Vascular Plant Recorder

2. over exploitation of plants and animals in
‘The introduction of alien species is interacting with habitat destruction and degradation,
over exploitation of plants and animals in
natural ecosystems, and global climatic change
to create an evolutionary revolution’
G.W. Cox (2004) Alien Species and Evolution

3. May lily - Maianthemum bifolia

4. London rocket – Sisymbrium irio

5. Are all Non-native Species Invasive?
Fodder vetch – Vicia villosa
Sand lucerne – Medicago sativa ssp. varia
Mexican fleabane – Erigeron karvinskianus
Sycamore – Acer pseudoplatanus

6. What characterises an invasive species?
“Invasive species are organisms (usually transported by humans) which successfully establish themselves in, and then overcome, otherwise intact, pre-existing native ecosystems.”

7. Perception, two non-natives:
Butterfly-bush - Buddleja davidii
A ‘Good’ Plant because:
butterflies like it
and other insects too
Japanese knotweed - Fallopia japonica
A ‘Bad’ Plant because:
it pushes over walls
butterflies don’t like it

8. Perception, two non-natives:
But should we not consider both ‘bad’?
Buddleia
evidence of benefit to butterflies and
other invertebrates is limited
potential evidence of adverse
impacts upon pollination biology
adverse impacts on calcareous grassland,
cliff and urban and brownfield habitats
Japanese knotweed
most butterflies don’t utilise it
(but some flies do)
it too damages built structures
adverse impacts on river margin
and woodland habitats

9. Changes: Native or non-native?
early meadow-grass - Poa infirma
annual meadow-grass - Poa annua

10. Pre 1969 distribution of early meadow-grass - Poa infirma
© Botanical Society of the British Isles

11. 1970 -1986 distribution of early meadow-grass - Poa infirma
© Botanical Society of the British Isles

12. 1987 -1999 distribution of early meadow-grass - Poa infirma
© Botanical Society of the British Isles

13. 2000 onwards distribution of early meadow-grass - Poa infirma
© Botanical Society of the British Isles

14. Changes: pseudo-natives’
wayfaring tree - Viburnum lantana

15. hawthorn – Crataegus x subsphaerica

16. foxglove tree - Paulownia tomentosa
Changes: Trees & Shrubs
foxglove tree - Paulownia tomentosa

17. tree-of-heaven – Ailanthus altissima

18. Tree-of-Heaven – Ailanthus altissima
© Botanical Society of the British Isles

19. Changes: Aquatics Valdivian duckweed - Lemna valdiviana
Least duckweed - Lemna minuta
Valdivian duckweed - Lemna valdiviana

20. Changes: native invaders
False oat-grass – Arrhenatherum elatius
Stinging nettle – Urtica dioica

21. Changes: Bulbous plants
Three-cornered leek - Allium triquetrum
Hybrid bluebell - Hyacinthoides x massartiana

22. Changes: pteridophytes
Cyrtomium sp. - house holly-fern
Pteris multifida - spider brake

23. Changes: bryophytes
Camphylopus introflexus

24. Changes: fungi
Agrocybe rivulosa

25. Vectors: Habitat creation and landscaping
Austrian chamomile - Anthemis austriaca
corncockle - Agrostemma githago
Vectors: Habitat creation and landscaping

26. Narrow-leaved ragwort - Senecio inaequidans
Vectors: Industry/transport
Narrow-leaved ragwort - Senecio inaequidans

27. Vectors: Horticulture
White ramping-fumitory - Fumaria capreolata
membranous nettle - Urtica membranacea

28. Evolving Ecologies: Assessing impacts Population biology
Inter-specific interaction
Variation in ecological function
Advent of further non-natives
Demise of natives

29. Collaboration: it can be done!
Creeping Water-primrose – Ludwigia grandiflora
False Hampshire-purslane – Ludwigia x kentiana

30. LISI: ‘Quick wins’ pale galingale - Cyperus eragrostis
Johnson-grass - Sorghum halepense

31. Chalara: how not to do it.