Typically a plants roots extend to the same horizonal distance as the foliage. So get as clost to that as reasonable; 1/2 may be okay, but 2/3 would be better.

first .... if you have good draining soil ... simply sink pots and all in one hole ... and loosely backfill ... the key is .. GET THEM DORMANT ... AND KEEP THEM DORMANT ... [wish i had a dime for each time i typed that in the last few weeks ...] if zone appropriate... temps are not important ... NO SUN ON POTS... they can easily thaw roots.. which then refreeze ... etc.. more than once.. and the plant will die ... and it wouldnt hurt to keep the plant out of blistering winter winds ... can do any of the following: north side of the house .... once frozen.. tip on side.. this avoids sun on pots.. and tipping in late dec avoids water accumulating in frozen soil ... buy 3 bales of straw.. and place against house.. and circle with bales... reduces wind ... and sun on pot or.. as above... dig hole in veggie garden.. and sink pots and all.. presuming you do NOT have clay soil ... review the KEY ... and you will succeed.. no matter which option you take ... it might be a great time to give them a thorough soaking .... ken

Hi Jeff; I was waiting for Bernergrrl to reply since I have not overwintered any cats yet. Fritilaries are really difficult and the original work involved drilling holes in wood blocks, soaking them and then putting the cats in them to overwinter. Jaret Daniels and some of the research I have read really emphasizes the importance of duff. From a federal website "Duff: Partially to fully decomposed organic material between the Litter-Lichen-Moss (LLM) stratum and mineral soil. Duff is described in two layers: an upper (Fermentation) layer and a lower (Humus) layer. " I don't know if they use it but I assume so. One of the problems that we are having in our forests and gardens is that earthworms are destroying this layer. Yes, earthworms are not butterfly friendly. They are not even native but are escapees from Europe and Asia. So, if you put your cats outside to overwinter, make sure there is enough debris for them to bury into. Assuming this is their habit. Another thing is making sure they have time to acclimate. If they are not outside now (are in your home) I would do it as soon as possible. Many animals, from insects to frogs, require the buildup of a glycol type chemical in their blood. This can take time and probably is in response to temperature fluctuations. I would think putting them in a cage with some peat or good high organic content soil then a lot of leaves would be fine. Then put the cage out in the elements, out of the sun but so rain and snow can get to it. You don't want them to dry out. The one thing to watch for is ants. We lose a lot of exposed chrysalises to them and I assume a sluggish caterpillar would not pose a problem for them. It ain't pretty. Here in SW Ohio I have not seen a silvery checkerspot. They should be common. I am worried about the species as a whole. I wonder if it is because they overwinter as cats. Once I read about earthworms and the damage they are doing to our forests, I can't look at them the same way :(. Let me know how it goes. I want to try to raise this species as well, Elisabeth

OK - that sounds good esther opal - I hope you didn't think I was belittling your information - if you did, I apologize. What is your zone? Do you get a lot of snow/frost heaving in your winter? I have lost quite a few plants, not just hosta which seem to weather the winter a little better than other, to frost heave. Sometimes almost all my hosta roots are above ground when I get to them in the spring. This year because of my back and not getting out to the garden, the deer and rabbits have been feasting! I am hoping the green stalks will provide enough green for the plants to gather a little strength. One other thread I have read suggests that I might be lucky! Thanks again for your help - and again I hope you didn't feel that I was just disregarding your information. There is so much knowledge out there - I sometimes get overwhelmed trying to sort out what could be the most beneficial path for me to take! Mind you, I understand that nothing is guaranteed. Jakki