I'll be interested in the columbines and the horseradish! I could send leaves from African Violets (two types), and also have many houseplants from which I could make cuttings. I have a million coleus seedlings because I didn't notice how many I had planted. :) I have many hostas, some of which likely have babies growing underneath them. Since I don't know their names, I don't know if they specifically grow in zone 4. I have a bunch of spirea japonica which looks to be a shrub that can handle zone 4.

There are some like Kaemferia (peacock gingers) that can be used as houseplants that are smallish growing for the most part, with attractive patterened leaves, but they like a dormant period, as they tend, like curcumas, to be naturally deciduous. Here in FL, they go down in the first real frost and come back up in late March/early April. Hedychiums (butterfly gingers) are evergreen, and many people grow them in large pots, but they may be too large growing for your purpose. Zingiber "Midnight" is a very attractive plant with deep green, almost black leaves that has lovely basilar "pinecone" leaves that come out yellow and fade tp a delectable cotton candy pink, and it might be a place for you to use. It is naturally deciduous to some degree, but never goes completely down, there is new growth coming out to replace the old canes that go down. This plant was being touted here the last 2 years as being hardy but it isn't, it has a very poor rate of return compared to other zingibers like Z. zerumbet, Z. "Milky Way", or even the common edible ginger from the supermarket (Z. officinale). I have had a large specimen in my greenhouse for 2 years and it always looks fabulous. SOme lovely plants that do make good houseplants are the Stromanthe, related to gingers. I may have a photo of it on my website, I can't remember: bihaisrainforest.4t.com

It needs a bigger pot. But I sugguest you plant it in the ground for summer and dig it up before the first freeze. It will multiply much faster in the ground. Put it in a 3-5 gallon pot when you dig it up. Unless you keep it very warm and give it lots of light it will go dormant. If it does do not water unless it's very dry and then only sparingly. Gingers do not get bushy. They always form a single stalk. It will spread side ways but one stalk at a time. Yours looks good for a years growth in that small pot.

The alpinias do not go dormant. Do NOT put them outside in winter. The blue ginger (which is really not a ginger), also does not go dormant and is also NOT hardy in you rzone. Do not leave it outside in winter. For the hedychiums, you are just inside their hardiness zone. I used to live in zone 6b and we always brought them inside (to the basement or garage) for the winter. This year, since they are still so new and have not yet become accustomed to the change in weather, put them in the garage or basement. Water only once every 2 weeks or so. Next year, after a summer of growth, you can bring some in and leave some out and see if they all make it. Then you know if your zone is acceptable to them. Better safe than sorry!