My sympathies, Salbwil! I moved about a dozen defoliated phlox stems into a fenced area (AKA Phlox Protection Zone) a few years ago and some of the phlox have come back there behind bars (note that woodchucks can climb fences if they're desperate). They haven't touched the lilies here, and they don't eat meadow phlox (Phlox maculata) which I have in abundance. Of course, that may because they happily eat the birdseed I put on the ground for birds and squirrels, and they're probably not terribly hungry. If it is a she, the babies are very cute. You can tell that my attitude is "If you can't beat them, you might as well enjoy them." Claire edit note: I just checked the date on the woodchuck baby photo and it was taken on June 10, 2013. That means that the next week or two is prime time for woodchuck babies to appear. Oh joy. This post was edited by claire on Wed, Jun 4, 14 at 13:46

In the UK we can get concrete pond sealant called G$ that you paint on. But although it clears when dry it DOES alter the colour a bit.

Cute as can be.

You want to seal both before AND after you grout. You seal the wood to discourage it from soaking up water like the sponge it is. After gluing and grouting you need to seal the grout with a grout sealer so no water gets into and under your tesserae. Wood outdoors is always iffy (depending on climate of course). Go into mosaicing wood for outdoors with the thought that it probably won't last forever and then you won't be disappointed.