hi george,

they do well outdoors in oregon, under some of the same conditions you've mentioned, though a bit warmer. they come back every year in my mom's garden. she doesn't mulch hers, but you might want to, considering your average temperature is a bit lower than ours.

-ming

I am also curious about the hardiness of begonias. I purchased some "bulbs" from Jackson and Perkins in their Harry and David outlet store in Medord about 3 months ago. Stuck them in the ground and waalaaa, here they are, One has one white bud on it. That is exciting. But how about the winters here. I am in Grants Pass, OR in the Applegate Valley. We are milder here than in other parts of our county, but we did have our first frost a couple of nights ago. If you feel I can leave them in the ground I will. I have enough that I want to bring indoors as it is. Help from anyone is appreciated.

Suzy

My kids always called that 'Grass Pants', Suzy. Started out as baby talk but it kinda stuck. Probably not 'politically correct', huh? If your begonias from Harry and David were regular tuberous types, I don't believe they'd be hardy. By now I'd think they'd be going dormant and you could dig them up and put them someplace like a closet to finish going dormant and then clean them up and store them above freezing in a paper bag. I think. Been a long time since I grew tuberous begonias--they don't like this climate.
As for the hardiness of others--the usual 'hardy begonia', B. evansiana, is I think hardy to about z6. The other ones recently advertised as hardy by Plant Delights nursery and Heronswood should tell you about hardiness on their websites. I know they both have varieties of evansiana which would I think be hardy as far as the species itself, and I think they and Yucca Do have others they say are hardy, but I haven't paid much attention since I don't really need to worry down here--I grow a lot of begonias outside all year around. Usually lose some foliage, but very seldom lose plants, and then it's either some of the ones that like heat and humidity and really love our summers, or something that doesn't get watered. I think more testing of hardiness needs to be done--probably there are more than we realize.