Self-set Allium problem
 

Anyone got any quick solutions to my plague of alliums? They're multiplying
at a furious rate. Seems ineffective to dig them out as each bulb produces
30-40 "offsrping" which "escape". We've tried "Roundup" weedkiller, but
they're incredibly hardy. Our only answer seems to be to dig out the
offending bed and replace the topsoil.

Help!!