User blog comment:StonerCatJay/Rereading the series- theories and speculation/@comment-3230060-20140522160420/@comment-3230060-20140523144940

if it is reiatsu and not flames, then by Ichigo's definition of a Getsuga you wrap the blade in your reiatsu and sling it at the bad guy. Which is what good old dad may have been doing. I suspect that got the getsuga from his father, and his blut from his mother. I don't think getsuga is something his mother passed down.

That said everything I've said so far is conjecture and should be taken with a grain of salt.