I live in Westland Michigan and what I do with my garden, which is my whole yard except for paths, to get ready for winter is nothing. Different species of butterflies and moths overwinter differently. Some overwinter as an egg, some as a larva, and some in a chrysalis, pupa, or cocoon. These wonderful little forms of Lepidoptera could be anywhere in the garden. They could be on plants, in leaf litter, or in the ground. I wait to break down my plants, which I drop to the ground to use as mulch, until sometime in May.
I have many trees which I grow in pots. Because of the size of my yard, which is only 60 by 120 feet, I don't have room to plant my trees in the yard. I grow these because I want to have as many host plants as possible in my yard, so that I will have as many different species as possible. Of butterflies, I have had over 30 different species.
The trees that I have in pots and the butterflies that lay their eggs on them are:
Black Cherry (Prunus serotina) and Choke Cherry (Prunus virginiana) – Eastern Tiger Swallowtail (Papilio glaucus), Striped Hairstreak (Satyrium liparops), Coral Hairstreak
(Satyrium titus), and Red-spotted Purple (Limenitis arthemis astyanax).
Sassafras (Sassafras albidum) – Spicebush Swallowtail (Papilio troilus).
Hop Tree (Ptelea trifoliata) and Prickly Ash (Zanthoxylum americanum) – Giant Swallowtail.
Chinquapin Oak (Quercus muehlenbergii) – Juvenal’s Duskywing (Erynnis juvenalis), Edwards’ Hairstreak (Satyrium edwardsii), Banded Hairstreak (Satyrium calanus).
Tulip Tree (Liriodendron tulipifera) – Eastern Tiger Swallowtail (Papilio glaucus).
Hackberry (Celtis occidentalis) – Hackberry Emperor (Asterocampa celtis), American Snout (Libytheana carinenta), Tawny Emperor (Asterocampa clyton), Mourning Cloak (Nymphalis antiopa), and Question Mark (Polygonia interrogationis).
Sandbar Willow (Salix interior), Pussy Willow (Salix discolor), Black Willow (Salix nigra), Corkscrew Willow (Salix matsudana) – Dreamy Duskywing (Erynnis icelus), Mourning Cloak (Nymphalis antiopa), Viceroy (Limenitis archippus), and Red-spotted Purple (Limenitis arthemis astyanax).
What I do with my potted trees is to move them behind my garage. I place them right next to each other and put mulch in between the pots, around the pots, and over the pots. The next spring when the leaves start growing, I move them back to the garden. Putting potted plants next to a building helps to protect them from wind. So by me putting the plants behind and next to the garage and by covering them with mulch it protects them from the wind and also keeps them warmer. This protects the roots. Whenever my trees start looking distressed, I remove them from the pot and cut off about 1/3 of the roots and then repot them.