Inventory of aliens escaping from culture
in the National Botanic Garden of Belgium
Anne Ronse
A bit of history: the domain in Meise
2 former castle estates: Meise and Bouchout
Empress Charlotte of Mexico
After 1938: a botanic garden
92.3 ha
•Greenhouses•open air collections•Buildings and roads•Woodlands•Grasslands and lawns•Ponds
Inventory of the flora of the domain
• From 2002 to 2011 • Wild and naturalized vascular
plants• Detailed results: per sector• Results in Scripta Botanica Belgica
n° 47 (2011)
Some results
• About 600 species recorded• 6 categories:
Category Name
Indigenous species
Local origin
escaped from
collections
Deliberate introduction
1 ‘Truly’ indigenous species
+ + - -
2 External neophytes - - - -
3 Garden escapes +/- +/- + -
4 ‘Stinsen’ plants - - - +
5 Wood lawn neophytes(Grassameneinkömmlinge)
- - - -
6 Indigenous introductions
+ +/- - +
Percentage of plant categories in the domain
Garden escapes: an important source of invasive exotic plants
• Australia: 66% of all plant species that have become naturalised are garden escapes (Groves et al. 2005) (increasing)
• The worlds 100 worst invasive organisms (Lowe et al. 2000): 56% of the plants are garden escapes
(Botanic) garden escapesBotanic gardens have played a significant role in the dissemination of invasive species worldwide (Hulme 2011).Botanic gardens were considered as naturalisation centres for plants by Devos (1870).
An example: Impatiens parviflora
Collection escapes in Meise• 180 species recorded• sometimes uncertain origin: escapes or not?
Duchesnea indica Cornus sericea
Collection escapes in Meise (2)• About 25% are indigenous species (regionally
or in Flanders)• Mostly from non-local or foreign origin
Oenanthe pimpinelloides
Collection escapes in Meise (3)
• 9 species from the list of invasive species in Belgium (Branquart et al. 2011)
• Watch list: Ambrosia artemisiifolia, Lysichiton americanus, Quercus rubra, Rhus typhina
• Black list: Ailanthus altissima, Cornus sericea, Crassula helmsii, Heracleum mantegazzianum, Mahonia aquifolium
Collection escapes in Meise (4)• 33% have not been recorded as neophyte before in Belgium• 85% of them have been recorded as naturalised outside
their natural range
Nothoscordum gracile
Cynanchum louisae
Collection escapes in Meise (5)• The numbers of plants for each escaped species varies between 1
to more than 100• The distance from the collections varies from 3m to 1000m
(maximal distance within domain)• The survival time for each escape is different, and is largely
dependent on the management• Means of dispersion: anemochory, zoochory, …
risk assessment for invasive species
Ranunculus parviflorus
Among the most persistent and numerous species are many woody species with fruits that are probably spread by birds, such as:
Diospyros lotus
Collection escapes in Meise (6)
Malus sargentii
Cotoneaster moupinense
Prunus lusitanica
Why woody plants? Woodland sectors are the less disturbed areas in the domain, as they are not weeded or mown.
Zoochory by birds seems a very efficient spreading method.
rose-ringed parakeetsPsittacula krameri
Collection escapes in Meise (6)
Have some species escaped from the Domain into the surroundings?
Yes, mainly woody species, such as Prunus lusitanica and Malus sargentii.
Some conclusions•Nearly one third of the spontaneously occurring species in the domain are escapes from the collections • Some species manage to escape outside the domain as well, especially woody species with fruits eaten by birds •the monitoring of the escapes at regular time intervals is advisable.