I'm part of the team that designed the 2012 USDA Plant Hardiness Zone Map. The zones are based on the average of the lowest temperatures each winter for the 30 years ending 2005. Then divided into 5 degree zones. But on the interactive map you can find out exactly what your average low temperature has been based on zip code, so you can know how close to a zone edge you might be. If you are zone 5a, your average low temperature over 30 years could be anywhere from -15 degree F to -20 degree F. But you get the same zone if your average is -15.1 as if it is -19.9. We specifically say that the temperature is based on the average, not the lowest it has ever been or the lowest it ever will be. But like they say about the stock market, past behavior is not a guarantee of future behavior. Of course, the scale of the USDA Plant Hardiness Zone Map only goes down to about one-quarter mile, so you still have to know the topography of your own garden. My official zone is 7a, but I'm really 6B because I'm surrounded by Rock Creek Park, the largest urban green space in the country. There isn't enough black top and concrete to hold the heat and lots of tree canopy (although less now after the derecho). Some genuses have Societies that are now doing independent testing for cold hardiness. But there is no real convention for using a particular amount of exposure as the basis for rating a variety--single night vs. multiple nights. Also, hardiness really depends on when the cold exposure comes. If the plant has a chance to be conditioned to colder temperatures in a gradual slide, it will be better able to survive than a sudden drop to a cold temperature. There is more scientific convention about the hardiness of agricultural crops, but it is still pretty loose. Mostly I think ornamental plant breeders just grab the hardiness zones on record for the species of a plant and who knows how precise those really were when they were recorded. That's one of the reasons I peruse and often buy from very reputable mail order nurseries like Plant Delights, who do a lot of their own testing of new varieties and tell you what they've found and if it differs from the label given by the breeder. I know this isn�t new information for many gardeners, but I thought I�d confirm what most of us believed.

I have lots of hostas in pots. I've read that turning them on their sides in place works, and I believe it. I have a dolly so I move mine into the garage and set them on the floor and forget about them from October to March. They do just fine; I've never lost one. This year I have more potted hostas so I might just turn some on their sides. Moving them into the garage is a chore, and they take up too much room in the garage anyway. It was hard to fit them all in there last year. I think the reason for turning them on their sides is to keep snow from piling up in the pots, then melting during a thaw, then the liquid freezes in the pots when it gets cold again. This freeze-thaw tends to happen here in New England in the spring, frequently. That cycle will break a terracotta pot. It will also destroy the cells in the roots and crowns if they absorb the melted snow when there is a thaw. I have dwarf alberta spruces in big pots on my deck; I turn them on their sides in the spring at the first sign of this cycle happening.

aw, Faye, the grass is always greener on the other side of the fence! I'm an animal; lover too and find your equine babies adorable. My purchase of some wide blade liriope muscari was from Plant Delights Nursery. It and the other big kind I got there wind up as tall as my knees. It is as tall as the dwarf nandinas planted behind it. Sort of a miscalculation on my part, but the nandinas are rather gold and red leafed, always leafed out, and then there is small boxwood dark green too behind that. My idea of a rather formal bed style in a basically undisciplined garden. This was for my New England husband's benefit. He loves it. ''Let me see if I have that picture of it. The liriope is the clumping kind. In parts of my Back40 space, the orphiopigon/monkey grass is the spreading kind. I don't mind it there. No lawn in that area. Keep the lawn mower out of the way. I can set pots of hosta down in it, not worry about the pots getting hot since they are shaded by it. But, this is almost the tropics here, and I just let it go. Other parts of the garden have the landscape fabric laid beneath the carnival midway shredded cypress mulch, because it is pathways and rows of potted hosta. Occasionally something persists to grow through the mulch, but it is easily eradicated. Here is the latest picture of the rows of really tall and wide bladed liriope. and here is signs of the spreaders, in a small area of the Back40 not covered by mulch oh yeah. On the right of that 2nd pic is some of the really big clumpinl muscari. Quite distinctive. I planted some of it in a pot with some tropicals ...

I just put one in yesterday- and have 2 more to plant in later this week- I am in zone 4. I don't even want to say how many more other perennials I have that need to be planted out.... YIKES! As long as the ground is not frozen- I will still try to plant most hardy perennials. I do however risk blowing out a hose from ice in the line because I know from experience that I must keep them well watered till the ground freezes. I have found with these later plantings to dig a bigger hole and mix my dirt with the pots dirt and fan out the roots to avoid heave. When I dig a hole just big enough to slide the plant out of the pot and put it in the ground, the difference between the plants dirt and my dirt promote heave, as does the shape of the undisturbed potted plant. I also have found that when I mulch heavily- if I do not expose/uncover to a normal depth in the EARLY spring, the pips may not thaw and grow normally- and I risk "Winter Rot". Leaving a heavy mulch over my hosta in the spring is the same as burying the crown too deep in my experience. Now that said- I have forgotten to plant some hosta divisions in the fall- and have left them laying on some dirt- in a BIG well draining pot all winter- only to find then in June happily doing just what they do- growing up to be lovely! I bet if you just banged them out of their pots and left them near the drive way..... Well, you know the rest.... Happy planting! Julie