The way to get tender roses through cold weather is to cover the tops with mulch or soil. The last time it got below 10 degrees F here a lot of roses died back or died - I would definitely do something to prepare for 2 degrees F if I had roses that were kinds I was concerned about. The temperature ranges for USDA Hardiness Zones are average annual minimum temperatures - individual temperatures being experienced at particular times don't really have anything to do with them. Think of your USDA low temperature spread as your core set, your mid-range, with it being normal for some winters to fall outside of it. The USDA web site tells people to plant stuff rated for the next coldest zone. Part of why this is a good idea is that so many commercial (and sometimes other) sources rate plants hardier than they actually are. It seems much of the time this may be due to a misunderstanding of what the USDA Hardiness Zone temperature indications refer to. This post was edited by bboy on Sun, Jan 5, 14 at 17:58

Larry.. i will try to simplify it for you ... in a few years.. lol .. your daughter can explain it to you .. lol OD is a descriptive term .... in the olden days... you could name a plant OD .... so there was an OD in a lot of different pines ... as listed above ... they have changed the rules .. and you have to use a real name now ... not a descriptive term ... i think that is the correct way to explain it ... here is an example you might under stand ... Pinus strobus 'Dragon eye Dirty diaper' .. a descriptive term ... lol .. think about it.. rotf .... more properly it should be Pinus strobus 'Pampers' ... or P. s. 'Luvs' or or P. s. 'White Cloud' ... or whatever version you have over the pond ... and you cant have Pinus strobus 'pampers' and a pinus koreansis 'pampers' .. and P thun. 'Pampers' .... the 'pampers' part is 'taken' with the first naming ....thereby avoiding confusion ... especially in Larry's head .. lol ... and mind you, mine.. and every body elses ... your confusion is actually the exact reason for the rule change .... right resin??? any clearer ..??? ken

I have a rosemary that is about 12 years old, and usually we have only weather in the teens a few times each winter, and only at night, so there is no problem. Last year, however, we had a cold snap of 7º, with 13-14º for highs for a week or two (no negatives here), which would kill normal rosemary. I "had" an arp, which died in this, even though it is supposedly resistant, but my big one I covered with a tarp, with a lamp inside, with a 100w bulb, sealed around the base with bricks as well as I could, and left it for 3 weeks, and the only problem was the brown tips on the branches where they were in contact with the tarp. This is how I keep my rosemary alive, and it has a trunk of about 2 1/2". Dave

"Quick conversion to degrees F: double the degrees C and add 30 :-)" That's only vaguely accurate, since 5/9 is vaguely similar to 1/2 and 30 is vaguely similar to 32. If you don't mind being off by a few degrees 100% of the time it's not bad, but the formula is a bit more complicated than that. Double the degrees C, subtract 10% and add 32. Or 5 degrees Celsius to 9 degrees Fahrenheit plus 32. And none of that makes it easy to see the relationship of the curve in the graph to degrees F unless you convert all the numbers. But anyway, as long as your res isn't colder than say about 62F you should be fine. Below that you can retard growth a little simply because the roots are cold.