Differences between Picea and Abies?

In a nutshell how does one differentiate between these 2 very similar genera of conifer?

 

One generally doesn't mind giving a handshake to Abies (spruce needles are generally pointy, fir needles tend to be pliable). Michael F, I'm sure, will answer in more detail.

 

Thanks Daniel!

 

Abies:
Twigs after leaves fall are fairly smooth, usually fairly thick
Mature cones upright, disintegrating to release seeds when ripe
Needles often (though not always!) blunt, usually medium length (mostly 2-5 cm)

Picea:
Twigs after leaves fall are rough with little 'pegs' (pulvini), usually fairly thin (thick on lead shoots)
Mature cones pendulous, opening but staying intact to release seeds when ripe
Needles often (though not always!) sharp, usually fairly short (mostly 1-3 cm)

Of course it gets a bit trickier when you add in Pseudotsuga and Tsuga, etc. ;-)

Pseudotsuga:
Twigs after leaves fall are fairly smooth, usually fairly thin (thick on lead shoots)
Mature cones pendulous, opening but staying intact to release seeds when ripe, with long bracts, medium (mostly 5-12 cm)
Needles often (though not always!) blunt, soft, medium length (mostly 2-4 cm)

Tsuga:
Twigs after leaves fall are fairly smooth, very slender; lead shoot drooping
Mature cones pendulous, opening but staying intact to release seeds when ripe, small (mostly under 3 cm)
Needles often (though not always!) blunt, soft, short (mostly 1-2 cm)

 

Great stuff Michael! Thanks

 

I have found very simply put abies have smooth bark picea is rough. Some exceptions may exist in the world, but this has not failed me yet...