Wow Gary.....That's a beauty.....What a gorgeous flower! Well done!
Keep it cold and dry(ish), next winter and you should get many more stems coming up all at once. Also, towards the end of summer, begin holding off on the fertilizer....especially nitrogen. It needs to starve a bit, to trigger the initiation of buds.
Very nice flower. I'm surprised that with the size of the plant you only have one spike. As John M. says, colder and dryer should help initiate more spikes. Well grown plant, too.
As cold as you can get; but, not down to freezing. Try to get your plants at least into the 50's F. If you can get them down into the 40's, that's better; but, it's also important to starve the plant for Nitrogen....or fertilizer altogether in the fall/winter to get the initiation. Once you see spikes, you can resume feeding normally again. This is how I got a stubborn, big, bushy plant of this species to finally spike for me. Meet it's every need and spoil it during the growing season, then, at the end of summer/early fall, this extreme rest will set spikes for late winter/spring flowers.
Thanks all. I was thinking that perhaps a bit more light in winter might be needed. I do not feed in winter, and also do not heat my grow area. The temperatures drop to 6-8 on some winter nights, while days are in the 20's. Not all nights go that cold, only when it drops to below zero at night.