I've been growing a BUNCH of varieties of hops down here in North Carolina for about a year and a half. I got 25 plants last year from B. Crosby Hops, Fresh Hops, and Thyme Gardens. The 25 plants consisted of 15 different varieties. The plants did very well, with most reaching the top of the coir yarn and going a foot or two over. I even harvested a couple of bowls of cones. There were only one or two varieties that 'under-performed' in this climate. To overwinter them, I gathered all the pots together and covered each one with about two inches of sphagnum moss to protect the crowns from frosts and squirrels. This spring I continued to amass more plants from new sources, and am up to about 25 varieties. Unfortunately, I noticed recently that the new rhizomes and crowns I have planted this year have gotten a MUCH better start than the plants left over from last season. At first I suspected lack of fertilization over the winter, or a smothering effect from the moss.
After going to a hop growers' conference last weekend (awesome!), I have a suspicion that the cause was actually a LACK of cold. One of the speakers mentioned hops' need for vernalization, which he explained was about six weeks of almost-freezing temperatures. We didn't get anywhere near that much cold weather down here! Far from covering the pots with a blanket of moss, I should have been putting them through the chill-chest in shifts... The lack of cold means that the hops are still in a halfway-dormant state; I think. The conference speaker mentioned using gibberellic acid as trigger to get the plants to wake up and go, so I've ordered a bit online and will spray a couple of 'duplicate' plants later on this week. I'm trying to attach two pictures of the stunted last-year plants, and one picture of a plant newly in the dirt this year. If anyone is interested in this, I'll be glad to let you know if the acid works.