First time in 10 years you've gone below freezing? Is that in a greenhouse? I tried numerous windmills in a cold z7a (Maryland) and was unsuccessful long term. That's with protection. I'd recommend trying a needle palm or yuccas.

No, that was outside. We very rarely go below 0. We average between 5 and 10 for our coldest night every year.

Freezing is 32F or 0C :-) And I'd bet that happens with considerable frequency in 6B!!

Without winter protection, I'd seriously doubt a windmill palm will overwinter successfully in your zone. As noted, they are pretty iffy in even a zone 7 location.

Whoops! I meant to say zero! Haha. Yes, we go below FREEZING every year!

What happened to it? Did the cold get to it?

Yes, cold killed it. I had it protected in a wire fence cage stuffed with leaves and wrapped in shrink wrap but just too cold. They don’t do well with long duration winters and can’t handle repeat temps below 10 F. One brief drop to 5F may not kill it but five drops to 10F with highs in the teens will kill them. Trachycarpus is not a z6b plant, more like 7b when north of Virginia since cold duration is longer. Needle palms will survive here, just buy several as not all will survive. I had 2 needles out this past winter unprotected and both are fine with no burn. Much hardier than Trachycarpus.

If you want, needle palms (Rhapidophyllum hystrix) can be grown as a houseplant until they get bigger.

http://w2.weather.gov/climate/xmacis.php?wfo=box

Monthly Lowest Min Temperature for Boston Area, MA

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual

2000 0 13 16 34 42 46 55 56 38 33 17 8 0

2001 12 10 17 32 38 50 56 58 48 34 29 23 10

2002 22 13 19 28 37 47 58 58 50 32 19 12 12

2003 1 0 9 28 39 50 59 55 49 33 27 16 0

2004 -7 12 21 30 40 49 59 56 47 38 24 6 -7

2005 -2 13 11 33 39 48 56 60 48 33 21 10 -2

2006 10 7 18 33 44 52 62 55 45 37 32 20 7

2007 3 8 5 28 42 50 56 55 47 37 22 17 3

2008 7 11 25 33 40 52 61 56 48 33 22 9 7

2009 6 8 14 34 45 48 58 56 46 34 35 10 6

2010 6 14 25 35 40 53 60 60 51 37 28 14 6

2011 -2 13 12 33 44 49 63 62 48 34 31 18 -2

2012 6 16 20 34 45 50 61 60 49 35 30 21 6

2013 4 15 21 31 40 53 60 59 44 35 18 9 4

2014 2 8 11 31 43 51 59 58 46 39 23 18 2

2015 -1 -3 9 30 39 46 59 61 48 31 28 24 -3

2016 8 -9 21 22 42 54 59 61 48 34 30 4 -9

2017 11 11 9 33 42 47 56 57 50 40 22 2 2

2018 -2 10 16 29 M M M M M M M M -2

I have seen that IF you add some heat into the shelters in winter that a Windmill palm can survive and do great. Heat is a string or 2 of incandescent Christmas lights woven into that shelter and use a "thermocube" or a "pipe heater" that you can find at any Home improvement store in the plumbing Dept. It comes on once the temps reach a certain temperature, like the ones at Home Depot come on when it goes below 39F and shut off once it reaches 59F. I use them in my greenhouse inside a small mini greenhouse for my tender plants since I am in zone 6a hardiness cold zone. Look on Youtube-" Growing palm trees in Avella, Pa". You'll see the shelters and the way the lights are used to provide heat inside the shelters. Avella, Pa is close to Pittsburgh, Pa so it is a zone 6b there and it will all work in zone 6a or maybe even lower since heat is added when needed, BTW, "incandescent" bulbs in Christmas lights are NOT LED lights, and I have ONLY found them at Home Depot stores, MOST places ONLY have LED lights and LED lights will NOT give off any heat. I hope this info helps someone.