Q: I recently read a story about Japanese Anemones being invasive and how a woman spent a whole year trying to get rid of them. Am I headed toward trouble if I plant them?
A: Well, they are aggressive, if they like you, but no worries until they break out in the lawn. My experience is that if you have spray-watering system and the area does not dry out, they are quite robust. If you lived in Berkley, or San Francisco, I would worry more.
The word invasive is quite misleading in this case. Invasive exotics are the bad plants that are invading the open spaces. The aggressive plants are the ones that we need to thin to control...but we can control them and keep them contained with some effort. Plenty of successful garden plants are a bit aggressive, that is why they do so well in gardens, they find an area they like and perform well. If some shrinking violet is pushed out of the way, so be it! These aggressive plants however, stay in their own territory and do not venture out into the wild and demand space.
Invasive plants, know no boundaries and this is a real problem in California. Some of those thugs have been recognized and are well advertised. They are becoming less available in the trade. Some sterile versions of the plants are available. There are some plants that are labeled sterile but end up setting seed, so I am not sure that the science is infallible. Well-intentioned science is a good start though.
There are a number of plants that we use in gardens all the time that are considered invasive. Before I get to naming names, let me say something about what makes a plant invasive and what the big deal is about those plants. When these survivors leave the garden, they sprout up all over the place. They fill in the waterways, clog the streams and often replace the plants that the native birds and other animals need to thrive (notice, not survive, thrive).
So who are these thugs any way? The that I mentioned last year is one. We have plenty down town and many more sprouting every day. How about Olive Trees? They sprout from seed. I saw plenty of them along Highway 80 today on my way home. The beloved Chinese Tallow Tree around the Camel Barn, you guessed it, invasive. Privits are invasive. They plague most of my clients and they can grow into 40 foot trees. Also Myoporum laetum, Black Locust and even some of the Pepper Trees are all invasive species. Figs, sadly edible Figs are pests.
There are common shrubs on the list too. Most heart breaking for many is the Pride of Madeira (so sad, that those big blue flowers are thugs). Some of the Cotoneasters, French Broom and Scotch Broom are a real problem. Algerian Ivy (the one with the big leaves) is awful for spreading. The European Blackberry is a real problem too.
For perennials and Grasses, lets start with the mean spirited Pampas Grass and move through assorted Mustards and of course Anise. Sadly Purple Fountain Grass (though not the dwarf form) is invasive.
The list goes on and on. I admit that I take this beyond the simplest solutions. This is the full inventory of (official) invasive species and declared by the California Invasive Plant Council (CAL IPC). For a consumer (really bad plants) publication, this is the place, The second link is a minimum that you should know before going to the nursery.
The question begs to be asked, do I ever use invasive plants in a design? I hope not, certainly not the ones on that last link. Invasive plants bug me. I know where plants came from and I want to see California natives in my hills. I wanted to see Greek plants in the hills of Greece, and Scottish plants in the hills of Scotland, you get the picture. I hope that you would like that too.
Your garden is yours to do with what you wish. It is just that a few plant choices are going to impact your whole neighborhood and others will stay close to home. So have a few aggressive species but please try to avoid the invaders of the Strait.
Thanks, Marilyn for the question. If you have a question, drop a line to:Alison@simplyperfectgardens.com