You might say that the woman next door has a green thumb if her garden continues to grow long after your plants have died.

VOA: special.2010.05.23

Someone who has the ability to grow plants well is said to have a green thumb.

VOA: special.2010.05.23

The index finger is the one next to the thumb;

VOA: special.2009.02.25

Then pinch the new shoots between your thumb and forefinger.

VOA: special.2009.10.06

the ring finger is third from the thumb.

VOA: special.2009.02.25