I have to say I disagree. The South, at least where I live in TN, gets cold weather too, though obviously nothing like the North; many of the ponds I've fertilized in the past had FA growing on the bottom to some extent all through the winter, and certainly had it growing when I first fertilized in the spring. More than a couple times, including once just over two months ago, I've fertilized a pond for the first time long after spring was fading into summer and the FA was already growing in large beds, covering in a few instances at least 20% of the lake. In every instance the FA was gone within a week. Sometimes it will grow more, briefly, with the application of the fertilizer, but as soon as the bloom happens the sunlight can no longer penetrate the water and the FA is going to die, pure and simple. That's just a basic scientific principle that is the same anywhere there's water and plankton and FA.

I would guess that Russ's pond is not extremely fertile naturally, because if it were fertile enough to get a good plankton bloom, he wouldn't have FA. FA is FA, and it requires sunlight to grow. And, some of the most naturally fertile ponds anywhere are in the South. I work with several phosphate pits, and I doubt that there are many ponds anywhere more naturally fertile than them.

Here are a few agencies, two state (MD, OH) and one multi-state, that recommend fertilizing in distinctly northern ponds, including several states that get colder than NY:

http://www.mdsg.umd.edu/programs/extension/aquaculture/finfish/factsheets/FF8/index.php

http://www.fish.washington.edu/wrac/images/wrac-104.PDF

http://www.dnr.state.oh.us/wildlife/Home/fishing/pond/fishproduction/tabid/6223/Default.aspx