Could it be a pot design issue? The least likely design to have freezing problems is one that is smaller at the bottom than the top, with outward-sloping sides. When the contents freezes, it tends to expand upward and outward, following the design of the pot. The most likely one to break is the one that is built like a cauldron, with a smaller bottom widening outward in the middle, then shrinking down again toward the top. The freezing contents become trapped and expand beyond what the pot shape can tolerate. The other problem is tufa itself. Organic materials rot away (peat, coir, sawdust, etc), leaving channels that water can move through and into. Some of it gets trapped when a freeze hits, and all those little bits of swelling ice weaken the tufa overall. A little bump the next year, and here you've got several pieces of one pot. If you've got a pot you're really proud of, plant into a removable cache pot, and put the tufa pot in the garage or shed for winter, after drying it out as well as possible. You can fight the laws of physics all you want, but you will lose. Just plain water carves canyons, rain wears down mountains, and tiny little bits of ice breaks pots. It's the Law. Sue

The only pot that has ever cracked was a concrete one that I did not make. It was under the deck on the back of the house and full of soil which froze and broke the planter. This planter had straight sides so it wasn't a matter of the sides slanting in. The directions I got with the planter from the manufacturer said not to leave it out over winter with just soil in it and if planted and sitting on the ground to break contact with the ground with a piece of wood. I have a couple with trees and I shove a piece of wood under them. Most of my hypertufa planters have trees or shrubs planted in them and they stay out all Winter. I use equal parts peat moss, sand and portland cement for most planters. By the way, even though that concrete planter cracked I really liked it so I still use it. I plant vines to cover the cracks. I have some nice size concrete urns from the same manufacturer. Their in Quakertown, Pa and they use to have a bargain area for concrete items with defects. I haven't been there in a while and I understand this place is only open on the weekends now.

Hi everyone, Thanks for looking/commenting, I really appreciate it. It really was a fun, easy project. Let's see, you can re-use the smooth molds (bowls etc) but not the baskets. Because of the basket weave, the hypertufa extends into the basket battern a bit so the outer basket needs to be cut away with pruners or a heavy duty pair of scissors. I just snipped a vertical line down the outer basket and then sort of ripped-open the outer basket shell to "free" the pot. The hypertufa was hard enough by then to not get highly marked by my snipping, but still soft enough (day #1) to let the basket go. It's much easier and quicker (and more re-usable) to use heavy, durable bowls, metal especially, but you get a different finish. I picked up the bowls and baskets at Goodwill for like a dollar each by the way. It was fun. I always also pick up some old silverware there too for potting work--forks, spoons, butter knives and even sharp bread knives come in very handy around the potting bench. I did spray the bowls with no-stick vegetable spray and then definitely helped them pop out. Having that nice big drop cloth (semi-disposable packing blanket actually) helped contain the mess. The recipe calls for portland *cement*, not concrete-with-rocks, so you could try concrete with rocks in it, but I used the recommended portland cement which you can just buy at any large hardware store. I'm looking forward to my next batch of pots and to seeing what other sorts of goodies we all could make from this stuff. It's fun and very easy so give it a try and post your results. Below is a link to the online version of the how-to article from Martha Stewart's March (maybe Feb) article. Thanks again for the nice replies. Take care, Grant Here is a link that might be useful: Hypertufa how-to from Martha Stewart

Image by: fuzzy Hypertufa covered plastic pot Plastic Pot Recycling - Hypertufa-Covered Pot Member fuzzy also revamped a large (gallon size) black plastic pot: Cover the outside of the pot with chickenwire, crimp it around the rim about 2" down and around the bottom about the same amount. Next, I turn it upside down and pack hypertufa (leaving the center drainage hole) all over the bottom and sides. A day later, flip it over and cover the rim and the 2" on the inside. A day after that, use some chickenwire scraps to rough up the outside. Now that the inside is invisible (because it's filled with dirt), you'd never know it's a black nursery pot... For more information and hypertufa "recipes" be sure to check out the Garden Web Hypertufa forum