Public Enemy no 1 seems to be the dreaded Mikania. At this time of year they appear in flower - previously un-noticed - all over the place. This one is in the swampy area just opposite the community garden.



If you look a bit closer you can see a mass of small flowers. It belongs to the family Compositae, which includes daisies and dandelions, and the seed is a small fluffy parachute that floats easily on the air.



So why is this so bad? Mainly because it scrambles over everything and shuts out the light. Even quite large trees can be starved of sunlight, their source of nourishment, and as a result they die. You can see this happening at various places around Lamma. This is in Tai Peng village on the path to Pak Kok.



Because the seed spreads so easily, it is very hard to eradicate. It's a bit like in The Day of the Triffids - it is here to stay and all we can do is deal with it as best we can. The best solution seems to be to pull it up whenever you see it. Fortunately it is not difficult to pull out of the ground and it has no nasty spines or thorns.

Wouldn't it be good if the crews who go out with strimmers to tidy up Lamma paths could start pulling up Mikania on a regular basis.
It's not so easy to get the roots out and stems set down roots very easily. Now is definitely the time for a concerted eradication effort before this season's seeds form and distribute themselves still further afield. .
According to Arthur Van Langenberg's invaluable book, "Urban Gardening," Mikania is a tropical American vine that was introduced to India during World War II as camouflage for military airports. Since that time it has continued to spread, covering everything within its reach at an alarming rate, earning the nickname Mile-a-minute weed.

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Member of Hong Kong Gardening Society

Sounds like a good idea, to spend a short time on Sunday going round and getting rid of the Mikania around the garden before it sets seed.

Public Enemy no 2 is deceptively pretty - if Mikania is Clyde, this is Bonny.

These pictures were taken in April when the plant - Oxalis, or pink wood sorrel - was flowering.





Why is this a pest then? Basically because it invades and dominates every patch of ground it encounters. The tiny seeds germinate to show the familiar three lobed leaves shaped like a clover or a shamrock. At the moment seeds are germinating and seedlings are appearing. Looking at the garden beds, you will notice a lot of these small Oxalis seedlings sprouting.



It's a good plan to get rid of them as soon as you see them unless you want the whole bed to be taken over. When the seedlings are still quite small they start to form small underground bulbs - this makes the roots very difficult to get rid of



There is another similar variety with yellow flowers.

Ah, so that's what these plants are called, growing in quite a few of my pots and even a corner of my rooftop garden now. I mistook them for clovers, silly me. They need lots of water and die very quickly, turning brown, if not watered for 2-3 days.

But why are they a pest exactly? They're covering the ground nicely and quickly, looking rather nice, not smothering or damaging the other much taller plants growing in the same soil, don't they?

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They are quite attractive and it calls into question what are weeds and what are not. It's really a matter of opinion rather than biology. The main problem with this species is that it takes over whether you like it or not, so if you have a plot dedicated to something else, it will be there trying to muscle its way in.

Meanwhile here's Public Enemy no 3 - I think this is called Zanthoxylum nitidum, a variety of Prickly Ash. The young shiny leaves and climbing stems are armed with vicious spines which positively enjoy tearing human flesh, as many have discovered when trying to clear patches of bush. The climber scrambles up trees and becomes woody, and the older stems retain very nasty sharp spines. Here's one from the community garden - I've cleared away the other creepers but left it as an exhibit until next weekend.

The Chinese call this the toothache plant, but I have no idea how it is used. Maybe if you get badly mauled by those spines any toothache fades into insignificance....
It is also a natural insecticide, but again I have no idea how to prepare or use it.

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Member of Hong Kong Gardening Society

Seems to be a very much more interesting plant than I thought. It's related to the Sichuan Pepper, and may have all sorts of medicinal uses. Well worth exploring because it's fairly common in the area of the garden. I had come to think of it as the bane of my gardening life - but I need to 'dig deeper' hey??
http://www.pfaf.org/database/plants.php ... um+nitidum
http://www.uni-graz.at/~katzer/engl/Zant_pip.html

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Here are a couple more shots of a younger plant in the area behind the seats. If you get entangled with one of these, it's quite difficult to get out without ripping your clothes.





PS I'm not sure I've correctly identified this plant - anybody else know?

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Member of Hong Kong Gardening Society