Must I wait until Spring? I live in a mild climate here in Elk Grove 95757 although it did hail yesterday! Sunny today and rain is forecasted for the next 3-4 days.

You want to wait to fertilize when the plant is in active growth, otherwise much of it will not be taken up and is wasted.

Ok i will wait until mid-March. Thanks so much!

Oh I forgot to ask, if I put compost or manure AND use the lawn food would that be too much nitrogen?

I doubt you need both, As I said, other than container plantings, I have never fertilized inground bamboo. One or the other would be fine and if it were me, I'd go with a compost first.

You can over-think fertilizing bamboos. They aren't that fussy. I have about 80 plants in the ground, and fertilized a lot of them by throwing on a handful of Osmocote slow-release fertilizer the first year. Now making sure they get enough water and are mulched a bit seems adequate.