Shamrock?

Can anyone help? In my veggie tunnel I have what I think is a South African plant but believe some gardeners refer to it as Shamrock. It has clover like leaves and develops multi corms in the ground sometimes with a carrot shape long tuber. It spreads very quickly with small seeds hardly visible. Last autumn I tried to spray down the ground with a pretty strong spray! No effect! I have tried digging them out individually - again no effect...

Any advice really welcome.

Thanks

Specklehen