I'm interested in buying a few Nandina's, it says zone 6-9. Have you found them to be fairly hardy, any feed back would be appreciated.
Some freezing back occurs here in western USDA 8. The cutoff seems to be around 10 degrees F. In this area a mildew problem has also arisen, with the cultivar sold using the marketing name Plum Passion appearing particularly apt to become spoiled.
Hardiness may be improved by the hot and wet summers back there ripening growth better, I don't know. In some eastern areas the plant has even become designated as a pest species. Other threads here mention it seeding out.
I grow Nandina domestica 'Firepower' here in Dayton Ohio with no problems other than it grows slowly here. The foliage turns a nice red color in the winter. A friend of mine up in southwest Ontario grows several different ones and gets berries as well. He's a zone 6 with lots of winter snow cover.
Cultivars can vary, but the species has been totally hardy (no winter dieback or damage whatsoever) around here even back when we still had a mid-zone-6 climate. Dirr reports strong regrowth after dieback from a -24 degrees F cold snap at Bernheim.
There was freezing to the ground in this area in 1990 and again in 2008. The 1990 damage (coldest winter in 30 years) was fairly general, the more recent episode some plants on some sites.
In 1990 I had just completed a planting on a property I was working on, in time for it to become defoliated. A large planting of a normally quite hardy, German origin rose cultivar was also installed there that fall, even these were killed back.
All because we got into single digits F. -24 would kill even the native trees here.
It is listed as an invasive species in PA......maybe not the best choice :-)
It is typically considered root hardy to zone 6 but foliage can suffer cold damage at various stages into zone 8, so exactly how evergreen the plant will remain in winter varies according to the severity of the winter. One source, which I cannot locate at the moment, even went so far as to list low temperature limits for the plant remaining fully evergreen, semi-evergreen, complete defoliation and total death. And different cultivars demonstrate differing degrees of "evergreen-ness". At a recent client visit, 'Plum Passion' in a somewhat protected location was completely defoliated (although new growth clearly evident) while a more exposed planting of the species experienced just a bit of foliage loss. The more compact forms, like 'Gulf Stream', often seem to experience less winter damage.
Not sure if you are looking at a specific cultivar but they are all pretty tough plants that require little care. The species is listed as hardy to zone 4.
The Firepowers seem to turn a deeper red when temps get cold in winter. I've never experienced dieback with winter low temp in single digits F.