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St John's Wort

Posted by Bronwyn 
St John's Wort
July 31, 2006 01:11AM
I have a dry, sunny garden under some trees so nothing much survives but I'd like to plant something that will cover up the ground. I thought of the groundcover St John's Wort but I don't know if it will be invasive. Have had enough trouble over the years getting rid of invasive plants without purposefully planting something that will be another invader! Does anyone know if it will get carried away on me?
Re: St John's Wort
July 31, 2006 05:27AM
I think St John's Wort may now be on the list of plants you are not supposed to plant. Mine was always well-behaved but I think there may be problems with seedings in native bush.
Re: St John's Wort
July 31, 2006 03:37PM
Yes, as PennyG says, St John's Wort is an undesirable plant, and there are several varieties of it listed in my 'Common Weeds of New Zealand'. I have a stream on my property and seedlings of St John's Wort constantly try to invade the banks. There are two native St John's worts but I still wouldn't plant them.

I would suggest trying the NZ native rengarenga, botanical name Arthropodium cirratum. Many people successfully grow great sweeps of it under pine trees and suchlike.

If you'd like to see a photo of it, go to the following link, then go down to where it says Arthropodium, and click on "group planting of rengarenga beneath trees":


Re: St John's Wort
July 31, 2006 07:13PM
Interesting. I have rengarenga elsewhere in the garden but thought they liked shade to part shade that was moist, I didn't know they'd grow in a hot, sunny, dry place with competition from tree roots.
Re: St John's Wort
July 31, 2006 08:33PM
Hi Bronwyn, you're right, they're possibly no good for areas with all day sun and I probably concentrated too much on your "under some trees" instead of your "sunny". I've had a few in pretty much all day sun and they're fine, but the frost is the one thing that makes them a little sad if they are in such an open spot. Maybe they tolerate the dry ground of pine trees and suchlike simply because they are shaded permanently by these evergreen trees.

Maybe you could look at some of the coprosma groundcovers - Coprosma "Hawera", Coprosma "Black Gold"...........?
Re: St John's Wort
August 02, 2006 02:54AM
Maybe also consider chionochloa flavicans? Or gossamer grass?
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