It has probably been 20 years since I planted about 20 Mountain Bell Allium bulbs in an area that was about 5 feet wide and 3 feet deep.  They were about even split between pink and blue varieties.   This area is in the edge of the woods and was overtaken by vinca several years ago.  Yet these bulbs have naturalized and spread over an area that’s at least twice as large and manage to find their way through the vinca to present me with blooms.  This clump of blue flowers has just started to bloom.