I bought two Nannorhops seedlings, each one with three leaves of about 5 to 10 inches long. I planted them around Christmas in winter and as it hasn't been much cold or wet and they got occasional protection against cold rain, they still look the same as in December.
We have got an exceptional cold summer this year that slowed down even the growth of our Dicksonia antarctica tree fern. It grew only significantly in April being with 75°F still the warmest month this year!

Both plants got already their mini-greenhouse since end of June but without sun those are pretty much useless and also with 70°F outside and an occasional sunny day they get only to 90°F inside. During night, temperatures fall again to 50°F or even 45°F, sometimes.
So, they still don't think to grow anyhow.
I was wondering if someone knows the minimum temperature for them to grow. I know getting some heating and adjust it to 100°F during day and 80°F at night will probably do the job, but it's about saving energy.

I also thought to dig them out and keep them indoors. But that would first require relative large pots and then we don't heat much our house in summer when it gets already to at least 70°F. But that seems to be early spring for the Nannorhops, again, and they won't grow neither, presumably.