Answer: Geum and Avens are names which usually refer to the same plant. This one needs no special winter care and should be fine as long as it was planted in a spot with truly excellent drainage, meaning not soggy in the winter time. Yarrow should also be fine without special care as long as it is in a well-drained spot -- yarrow is a very sturdy plant. You might wish to mulch, using several inches of organic material such as shredded bark, around the plants but not over top of them. This will help moderate the soil temperature and help reduce winter freezing and thawing which can pop plants out of the ground.
Unfortunately, I am not clear about all of the plants on your list. Bluemoon and dragon head and sandwort are not ringing any bells at the moment -- this is a good example of the problem with using common names. To be honest rather than worrying about individual plants you might want to take a look at a couple of basic books about perennial gardening and then use that along with first hand experience to see what does and doesn't work for you.
Beginning perennial gardeners are often bewildered by the variety of plants and strident recommendations about plant care (often contradictory) and the apparently specialized care every plant seems to require, but in practice there are some basic principles which seem to apply in many cases. Deadheading for instance always requires removing the entire flower so that the future seed capsule is removed, division of fibrous rooted plants is a fairly consistent procedure. Once you have observed your plants for a year or two much of it will make more sense, too. Remember that plants are made to grow and that there are varying degrees of assisting them to do that -- some gardeners follow a very laissez faire approach and others putter incessantly. It is a matter of personal style and enjoyment!
Here are some books you may find helpful.
You might find some more specific ideas in a basic book or two about perennials. Here are some you may find helpful: "Perennials for Dummies" by Marcia Tatroe ISBN 0764550306; "Rodale's Illustrated Encyclopedia of Perennials" by Ellen Phillips and C. Colston Burrell ISBN: 0875965709; and "The Well-Tended Perennial Garden : Planting & Pruning Techniques" by Tracy Disabato-Aust, Steven M. Still ISBN: 0881924148.
Another approach is to find an experienced gardener who will show you these things -- there is no substitute for simply seeing it done once, or trying it yourself! Enjoy your garden!
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