[ritamax]

There are some different lists of invasive plants in internet, can you say which are trustworthy and how should one go on with them? Dig out the invasive plants?

[David Bracey]

The most reliable is http://www.eppo.int/INVASIVE_PLANTS/ias_plants.htm however it may not be complete and there are probably other good sites. I think you need to identify invasive plants at the seedling as well as the adult stage.  Clearly it is easier to deal with seedlings than trees.

[ritamax]

Thanks a lot! I found a Spanish government's list of invasive plants in Spain (www.magrama.gob.es) in internet and was quite shocked to find out, that not only the weeds and the common known invasive plants (cortaderia selloana, acacias, buddleja davidii, mahonia, ricinus communis, arundo donax, helianthus tuberosus, rhus typhina, phytolacca, prunus laurocerasus etc.), but also most of the garden plants you see in Costa Blanca private gardens, in the nature and in garden centers are considered invasive (agaves, aloes, opuntias, lantanas, bougainvillea glabra, carbobrotus edulis, ipomoea sp, impatiens sp, passiflora caerulea, bidens sp, pennisetum setaceum, tropaeolum majus, senecio cineraria, mirabilis jalapa, kalanchoe sp, pittosporum, yucca aloifolia, crassulas etc.). Also many trees like Schinus molle is on this list, I just planted it. And ficuses, which I have 3 different and they are 3-4 meters high. My garden is not a huge problem though, as the weed fabric and the stone chippings cover the most of it and keep weeds down. I have planted through the fabric and not so many from the invasives' list (only aloe arborescens). I have only a couple of stripes without the fabric and I do weed thoroughly every time I go there (every 2-3 months). But I think I have to dig out the old lantana camaras from the previous owner. It is difficult to find Spanish native plants in garden centers and I don't grow from seed as I am absent most of the time. But I feel this is an issue to consider seriously.

[Fleur Pavlidis]

I wonder if the author of the list you found has simply done a copy and paste job on all the plants considered invasive anywhere? I expect the you can see from looking round that most of the plants on the list aren't invasive in your area despite being used in gardens. Here in southern Greece we have Oxalis pes-caprae, Ailanthus altissima which are truly invasive - widely spread outside gardens and impossible to eradicate, and other species which can be invasive locally like Opuntia vulgaris and Robinia pseudoacacia. Anyone doing largescale public planting obviously has to be aware of potential invasive species and be careful of escapes into the wild but I think it's a fairly minor concern for most gardeners. Not one of my plants has ever jumped the fence, but I'm delighted to say the natural importation of wild plants is still going ahead.

[ritamax]

Well, I don't have any reason to doubt the list "El Atlas de plantas invasoras en España", which is given on the web site of the ministry of environment in Spain ("magrama" is Ministerio de agricultura, alimentacion y medio ambiente), it seems very thoroughly done with a lot of explonations and photos on the subject. They have in addition much shorter lists of the most invasive plants for every region. In my region between Alicante and Murcia with a very warm, sunny and arid conditions with a warm, dry winter (this winter rain only 3 times) the list contains plants like agave americana, opuntias, carbobrotus edulis and lantana camara, as they do grow like mad and you see them run out of the gardens. Arundo donax is a problem, but also common garden plants like passiflora caerulea, tropaeolum majus, mirabilis jalapa, some ipomoeas are on this list for my region. There are very few native trees growing, but a lot of invasive considered acacias, eucalyptus, parkinsonia, schinus molle and palmtrees, which are affected by picudo rojo. So, the situation is probably worse than in other places. I for myself found a nursery with native plants and an online shop for seeds www.semillassilvestres.com , so I will try to be conscious about this matter. In Switzerland, where I garden as well, is the situation very different, but there are some problems here as well because of the mild viticultural climate (here invasive are Ailanthus, Heracleum, Rhus typhina, Robinia pseudoacacia, Lonicera japonica, Solidago, Ambrosia etc., perhaps the same plants that are invasive in cooler mediterranean climates).

[Marilyn]

Dear Rita,

I can give you a comparison with Portugal; the Iberian peninsula shares a fair bit in terms of conditions and flora. I am not surprised to see many of the subjects on the extended list. Agaves and aloes do spread here though I would hesitate to call them really "invasive"; pennisetum setaceum, mirabilis jalapa, opuntias and lantanas are somewhat worse. Carbobrotus edulis is an absolute horror, especially at the coast it creates huge carpets which prevent anything else from getting a shoe in. Ipomoea indica is on our list but again, I have not seen it being very scary. Things do change from region to region according to microclimate though. I have to say, though, I have never known Schinus molle to sprout from seeds here, we have a lot of them in the garden and they are forever making seeds, but this is not the first time I wonder if it is like Ficus, needing a special pollinator which did not survive migration with the plant, and without the pollinator it makes sterile fruits.

As a rule of thumb, I would say look very carefully at your surroundings before planting something from the list, to see if it really is invasive in your region. You will soon find it in the local landscape if it's a problem.

[ezeiza]

Rita, Arundo donax, if you have a chipper/shredder, makes a superb mulch and soil conditioner.

The problem with alien plants in a new environment is their ability to vary from seed and thus new races are being selected all the time, sometimes slowly, sometimes like lightning. This is why introduced plants that were seldom seen years ago, can become incontrolable pests later.

[ritamax]

Thank you, Marilyn and ezeiza, for your valuable advice! I think the problem in my neighbourhood in Orihuela Costa is, that it used to be just sand and salinas and erosion before they started to build in 1970's. Every house got its garden with a "grama" lawn (I think it is the Cynodon dactylon), cypress hedge, bougainvilleas, palm trees with the irrigation system with sprinklers. The heat and the watering plus the use of chemicals makes everything grow uncontrollably. The street trees are pines and oleanders, which thrive very well. If you go around, you see lantanas, agave, opuntia etc. in places where they don't belong, often coming through asphalt. Many common garden climbers run away in a second. There are practically no native plants to be seen. I just found a nursery specialized in them, which I will check out the next time. Marilyn, I really enjoyed your article in the last MGS journal, your project is great and that is what I will try to do in my smallish garden of 350 m2. But do I ever get rid of the irrigation system, if I am not living there and having a cypress hedge? The hedges which are not watered, get brown. But how do the native plants react to the overhead irrigation? So how to put everything together is very interesting.
Ezeiza, thanks for the tip with arundo donax, it groes everywhere (but not in my garden and I don't have a shredder, yet). Olivier Filippi advices in his book not to use any compost or manure. My soil is clay with sand and stones, if I put even more sand in, it is good for lavender and rosmarine, but how about exotic mediterraneans like Callistemon, Grevillea, Metrosideros, Ceanothus and Tecomaria, which I already have in the garden? What else could one work in when planting? I have a weed membrane with stone chippings over, so the weeds are not a problem anymore. 
 

[greengrass]

Hi,
Do remember that invasive plants poses the very thing you need here in the med - thats the ability to survive where others don't. I am of course thinking of grasses for lawns here, as its the ability to survive without water for long periods and a deep root system makes them almost indestructable.

This characteristic can also be harnessed to good use.
For drought tolerant grasses and more free info see www.lawnsinspain.com

Regards
Greengrass

[Alice]

I would add Acacia saligna (A. cyanophylla) and Lantana camara to Fleur's list. The first, especially self-seeds everywhere, though I also have not seen it growing in uncultivated land outside the garden.

[Alice]

Could anybody who grows Mirabilis jalapa in southern Greece or somewhere equally dry let me know how invasive it is within the garden. I have read that it grows where the seed falls, i.e. near the parent plant. I would like to grow it for colour but don't want it spreading around too much.

[Fleur Pavlidis]

Here in Attica I've found that it doesn't spread much around the garden but it will colonise small areas and is almost impossible to eradicate from among other plants because of the deep swollen roots. I had to empty a big planter it had got into because the other plants had died and I found that these roots had grown massive below the surface. I'd avoid it.

[Alice]

Thanks, Fleur. That is useful to know.

[John J]

Alice, I'd echo Fleur's advice. We have it in one of our areas and it's a real thug, we try to get rid of them as they appear but they keep coming back.

[Alice]

Thank you for your feedback, John.
They don't sound like a good idea at all. We had a similar experience with a couple of agaves some years ago - we couldn't kill the things!
Pity, because I had just bought some tubers. Perhaps I should find them a home in the UK.