Herbs as garden escapees and weeds

ladyhanaApril 25, 2009

I read the thread on evening primrose with interest as it is a noxious weed here. It has prompted me to ask if there are other herbs that should be treated with caution for their invasive potential.

I realise that this will change from region to region. For instance the lantana that is such a pest in Queensland is kept under control by the hot dry conditions here.

Here's a few that were deliberately planted in my garden (some by previous owners) and have since attempted world domination;

Thistles (cardoon, blessed and milk thistles) - spread by seed

Oak Leaf Lettuce - spread by seed

Citronella grass - spread both by seed and runners

Nettles - seed

Cestrum - this one is a real pain, stinky horrible thing spread by birds

Olive - birds eating the fruit

Centella asiatica (swamp pennywort) - took over my shade-house spreading through runners

Warragul Greens - spread through seed

Moth mullein - seeds itself freely in my pavers

Rocket (Arugula) - seeds itself in the gardens and lawn

Melissa (both lime and lemonbalm) - taken over large sections of garden borders spreading both through runners and seed

Yarrow - spreads through runners

Castor Oil Plant - seeds come over from my neighbor's garden via bird poo

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fatamorgana2121(Zone 5/6)

It is always interesting to see what may be "invasive" to different gardeners in different locations. Being in a place that is below or near freezing half the year (or at least it seems that way!), I can't ever imagine having olives being invasive or not liking some olive trees growing about. ;)

Thanks for sharing!


    Bookmark   April 25, 2009 at 8:47AM
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G'day, fellow Aussie!

There are literally thousands of 'herbs' which are potential weeds. After all, a weed is just a useful plant that is growing where you don't want it!

It never ceased to amaze me, when I was 'commercial', that dandelion was my top seller! Others that sold well were stinging nettle, assorted sorrels, chickweed, lamb's quarter and other chenopodiums.

One of my worst ever weeds (apart from evening primrose!) was Amaranth. It took years to eradicate all the self-seeded volunteers.

St John's Wort is also classified as a noxious weed in many parts of the world.

Others that spring to mind include Bergamot, Burdock, Catnip, all the Clovers, Comfrey, Datura, Feverfew, Goldenrod, Ground Ivy, Horehound, Horseradish, Horsetail, Lady's Bedstraw, Oregano, most if not all of the Mints, Motherwort, Nasturtium, Purple Loosestrife, the Brooms, Purslane, Scullcap, Soapwort, Sweet Annie, Vervain, Liquorice.

(OK, some of those didn't just spring to mind! I did a quick search on my data base! I didn't include all in my list, just the best-known ones.)

In parts of Australia, two more really troublesome weeds are Blackberry and Prickly Pear.

I'd be loathe to describe Parsley as a weed, but I've had it self-seed in all sorts of unwanted places, including between concrete pavers. Same with lettuce allowed to go to seed.

I've always been intrigued by the fact that in many parts of Europe, people nurture their (usually potted) geraniums as they would a premature baby. In my part of the world, geraniums become huge, and the only way to control them is to hack them back on a regular basis.

A friend of mine gave me a Brahmi plant - that was something I could watch growing, and not get bored. It had to go, but I had to be careful disposing of it because once that stuff gets into the waterways, it becomes a real thug.

    Bookmark   April 25, 2009 at 6:52PM
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Thanks Daisy, you added a few I had forgotten. It's very dry here, so most of those are easily controlled... I actually wind up nursing many through the Summer and have given up on others. I never put mint or goldenrod in the ground.
I remember the look of amazement on the face of an American friend when she saw poinsettia trees here, probably the same look I wore when I saw a full sized Ficus Lyrata in Brisbane!
I have a zombie olive tree in my back yard. I have repeatedly cut down, poisoned and dug this monster out.. even got in a backhoe to grind the roots down to three feet or more below the ground... and it rises from the dead each time. I have not let the thing fruit for three years and I am still pulling up olive seedlings. The Olive trees that have taken over large areas of the Adelaide hills contribute hugely to the problem of wildfires in Summer. They are fighting for domination with Hawthorn, Blackberry, Boneseed and Broom.

    Bookmark   April 25, 2009 at 7:25PM
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