We have two of these that we planted 5 years ago. Back then they were in 8" pots and only a foot tall and slightly wider. Every summer when the sun reached them, Deb would cover them with shade cloth. And she made me cover them with blankets in the winter when there was a chance of freezing temps. Then year or two ago, we heard someone on a Saturday morning radio gardening program say to let them go and they will acclimate themselves and those precautions would no longer be necessary. That was about the same time I adopted a staunch "Survival of the Fittest" plant policy so I promptly bought into that!
The fronds burnt that summer and they got nipped by frost that winter. Now the weather doesn't bother them a bit. As you can see they are quite healthy.
