[ritamax]

Spain has a law since Dec2011 concerning invasive plants. It is now against the law to possess, sell, import and export following plants:
IN ALL SPAIN (if not indicated otherwise):
Acacia dealbata (permitted in Canary and Balearic Islands, prohibited in the peninsula)
Agave americana
Ailanthus altissima (permitted in Canary Islands)
Alternanthera philoxeroides
Ambrosia artemisiifolia
Araujia sericifera
Asparagus asparagoides
Azolla spp.
Baccharis halimifolia L.
Buddleja davidii
Cabomba caroliniana
Carpobrotus acinaciformis, C. edulis (permitted in Canary Islands)
Cortaderia spp. (permitted in Canary Islands)
Cylindropuntia tunicata
Egeria densa
Eichhornia crassipes
Elodea canadensis (permitted in Canary Islands)
Fallopia japonica / Reynoutria japonica
Helianthus tuberosus
Heracleum mantegazzianum
Ludwigia spp.(except L.palustris)
Myriophyllum aquaticum
Opuntia dillenii, O. maxima, Opuntia stricta
Pennisetum setaceum
Pistia stratiotes
Salvinia spp.
Senecio inaequidens
Spartina alterniflora, S. densiflora, Spartina patens
Tradescantia fluminensis
Prohibited in BALEARIC ISLANDS:
Cotula coronopifolia
Pennisetum villosum
Pennisetum clandestinum
Prohibited in CANARY ISLANDS:
Acacia farnesiana and A. salicina
Ageratina adenophora and A. riparia
Arundo donax
Atriplex semilunaris
Calotropis procera
Cyrtomium falcatum
Furcraea foetida
Ipomoea indica
Leucaena leucocephala
Maireana brevifolia
Nassella neesiana
Pennisetum clandestinum
Pennisetum purpureum
Phoenix dactylifera
Ulex europaeus
It is noted, that 3/4 of the invasive plants in Spain originate from gardening and floristic practices.

[Alisdair]

You can find the full text of the law by clicking here, with fuller lists of the plants involved. The key section seems to be Article 8 - though as far as my very shaky Spanish allowed me, I couldn't see any real system of enforcement included.

[ritamax]

The list I gave is from this bulletin and is the full list of "forbidden plants". I just organized them in a clearer order. The longer list Anexo II consists the plants considered potentially invasive, but they are not forbidden. In Canary Islands, where much more plants are forbidden than in Spain, amongst them Aloe vera and Figtree, there is a heaty discussion going on, but on the list for peninsula there are almost only decorative plants.

[andrewsloan]

I tried to read the bulletin but it is very long-winded. There is also a list of plants with "invasion potential" of which I seem to have a few in the garden eg Aeonium, Lantana, Aloe Vera, Centranthus Ruber etc.

[ritamax]

The list of "potentially invasive" is huge, therefore I have put only this list forbidden invasives here, as it is very difficult to avoid all the plants on these huge lists. It is of course advisable to cut out the seed pods and not to throw rests of these plants to the nature or even the compost heap. It is actually common practice to forbid to import/export invasives, Switzerland has done the same thing. I was just now in Southern France near the Spanish border, and there the botanical garden was also informing about the worst invasives as opuntia, agave americana and carbobrotus edulis.   

[david glen]

I have read the sections of the law to which Alistair has provided a link.  The law proscribes the new propagation , sale etc. etc. of the species listed, but does not require that plants (before the passing of the law) cultivated in public parks, private gardens and others be destroyed. Article 15, Disp. trans quarta on page 132724 makes this clear.  So nurseries should not be selling them and MGS parties should not be passing on cuttings!

A glance at the countryside (that part which is not cultivated) in neglected places here in Tarragona and worse around Barcelona in residential zones illustrates what the law is trying to curb. Acacies, Apuntias, Ailanthuses (?) are a menace. Some I love, but do recognise that they are pests. The Agave is perhaps the very worst. They are effective as a barrier and solitary are a sculpture, but once they flower how do you recycle it? The answer is in a useful article in a previous issue of the journal.... The solution is not to plant them in the first place.  They are after all an introduced species, but that's another story.