Is this a phyllostachys? If so, yes it could take up to 5 years for rhizomes to grow and spread before culms pop up for some phyllo species.

Phyllostachys is usually abbreviated "Ph." as there are other bamboos where the genus starts with "P".

Yes it is a Phyllostachys. Sorry about the "P" but I assumed posters here would recognize it at the species level with the Dulcis indicated. Does anyone have anymore specific info about Dulcis? I have other Phyllostachys varieties and all have put up culms after their first year in the ground. If my Dulcis is just spreading right now, how much of a spread (i.e. in feet / diameter) can I expect when it does start to pop? Thanks for all your wisdom in advance.

Is the dulcis healthy above ground? If so, don't fret, you'll be eating sweetshoots in no time.

Lewis bamboo has on their site a picture of a dug up transplanted bamboo that hadn't put up shoots in 3 years.
http://www.lewisbamboo.com/habits.html
and quote "This is a good example of a
a bamboo division that, to
most gardeners, would appear
to be doing nothing. However,
underground it was about to
explode with many shoots the
next Spring. It had not put
up any above ground culms
in its three years of growth.
Upon digging and counting the
buds on the rhizome, I estimate
that if I had not disturbed it,
there would have been over
12 new canes (culms) emerging
this next Spring. "

As indicated above, bamboo grows without your feelings as a consideration. As I stated above, If its healthy above ground, you shouldn't worry about below ground. The plants sometimes run on their own clock to the displeasure of the caretakers.

I have dulcis, I would dig a bit down and just take a peek and see if they are indeed rhizomes. Mine tend to be very shallow and mine shoots in May in the Dallas area. I have had mine a few years and they have shot up every year. Hopefully I get 1.5 inch culms this spring. I did have alot of them die off though. Only about half the shoots that came up made it, they others turned into wet noodles and died. I also did put in a concrete barrier and it did have a small openning in one corner. Guess what? it found it in one year so this is a very fast spreader and not much of a clumping runner.