Green Thumb vs Black Thumb

A friend of mine bought a house, just like me,  this past winter and has been equally possessed with the gardening bug.  There is nothing like a new house with a neglected yard/garden/patio to bring out the mad nursery maven in us all.   Her yard is huge (she doesn't live downtown),  and it is about 50% sun, 50% shade, just like mine.  Now, after several strong months of gardening time there is one major difference.   My garden is growing and her's isn't.  At all.  I don't know what she's doing over there, but I'm scared to bring her the huge pot of nasturtiums I grew for her that is now blooming.   

Nasturtiums on Death Row

Now, I am very very happy my garden is blooming but, same as her garden,  I don't know what I'm doing so right that every single thing has pretty much made it.  Even the seeds.  Okay, not the lily bulbs but truly, I had no control over that.  That was the 3:1 squirrel to plant ratio.

Maybe its that I grew up basically in a massive garden and know a lot about various plants from osmosis, and she grew up in the middle of Okinawa?

Maybe its that I don't travel for a job and have been here each and every day to make sure everybody out there is safe 'n sound?

Is it that I'm addicted to gardening magazines?  Reading gardening blogs?   Am I just lucking out? (please don't let it be this because massive die off when the luck runs out would be the end of me). Does she have some invincible invisible pest problem?   Its those Japanese seed packets right... they fail to grow on foreign soil?  But from what I can tell Japanese tomato seeds sure do look a lot like the ones here, they just have prettier calligraphied names.

Or are you really born with either black or green thumbs? And what does that mean exactly?  How does one help another one overcome blackthumbotosis? How do you keep from catching it?!