Stressing the yeast

I had just bought the White Labs WLP 351. I heard somewhere that if you under pitch the yeast you will stress it out and release more phenols and make it tase better. Is that true and if you do how much do you underpitch? Half the starter? More or less?

no i think your wrong with that.

Some sources do say that underpitching yeast in a weizen helps develop the flavors. Not sure how true that really is, but people do it. If your gravity is below 1.050 on a 5g batch, just pitching the tube would be considered underpitching.

As was mentioned by Edcculus, I can see this being true for something like a weizen, but you'd be better off just fermenting a few degrees warmer than you normally would instead of messing with under pitching.

Under pitching should never really be a technique used to elicit flavours, IMO. You bring along a whole host of other issues if you under pitch, such as poor attenuation which can REALLY screw with the balance of a beer. Even if you were to try under pitching to increase ester/phenol production, there is little way to make an exact science out of it without tons of trial and error with your beer.

I have never under pitched to achieve that type of flavor, but have had good success with fermenting with temps that were a little bit higher than normal.

Temp is the way to go. I will do that. Should I make a starter or pitch the vial?

I always do a starter.