Anyone out there have any ideas for a barrier between lawn and plastic pool garden? I'm thinking of a kind of soil "no-man's land", populated with grasses or skunk cabbage or similar that would soak up any fertilizer before it hit the edge of the pool-bog.

If anyone is interested, I'll post some pics of the proposed site so you can get a better understanding of the dynamics.
Looking forward to reading your thoughts.

Strange as it may sound the first step to building a bog garden, dig a hole! The area can be whatever shape you like about 18 – 24 inches deep and slightly raised from the surrounding bed area to keep runoff from entering the bog (this is explained shortly). Locate the bog garden where it will get full sun at least half the day, preferably afternoon sun.
The worst part is done! Now line the hole with rubber pond liner. Don’t worry if there are sharp roots etc. that could puncture the liner. A few leaks do not matter.
Begin filling the bog with the following combination: add 1 bale (4cuft) of sphagnum peat, mix in 100lbs of silica sand and a big mess of conifer needles (white pine is my favorite). Add rain, distilled, or dehumidifier water till saturated. This is the second hardest job because peat is extremely hydrophobic. Repeat above until the bog is full and fully saturated. Sculpt the "dirt" such that it is low in the center and higher around the edges. Because it is saturated and all the air is worked out, it will not settle.
If you wish to plant a Fen type garden (ph neutral and slightly more nutrient rich) add 50 – 100 lbs of calcium rich lime in place of the conifer needles. Most species of Cypripedium will prefer this to the bog garden. I made the mistake of using crushed oyster shell, it added too much salt…so don’t use this for calcium!
Time to plant! Place plants that like more water near the center of the bog where it is low and plants that like less water around the edges. This works well because the edges dry out far faster than the center. Be patient! A bog garden takes at least 2 years to become well established as a mini ecosystem. Don’t pull any weeds that you are not sure are weeds! Some really good stuff can come to your garden from peat bales. But keep seed heads of sedges and other more aggressive plants trimmed so more tender plants will have a better chance of survival.
The cardinal rule! NEVER EVER EVER WATER WITH ANYTHING OTHER THAN RAIN, DISTILLED, OR DEHUMIDIFIER WATER! TAP WATER WILL KILL A BOG GARDEN IN A SEASON AS WILL ANY SORT OF FERTILIZER!
Plants suitable for bog gardens and sources

There are a number of plants that are suitable for bog gardens, many are readily available others far too scarce. Listed here are some of the plants I have had success with and enjoy in my garden. Remember when looking for plants, be sure to buy from sources that propagate their stock or (in the case of orchids) are from documented salvage operations. These are plants that were removed from habitats just before the bulldozers come in to build the next strip mall. This list is NOT exhaustive and you may have luck with plants I have failed with or think I’m crazy for planting "that".

CARNIVOROUS PLANTS
Sundews, Drosera filiformis, D. rotudifolia, and D. intermedia
Sarracenia Species especially purpurea and those that produce best pitchers in spring.
Venus Fly Trap Dionea muscipula. I’ve found it reasonably hardy here (my plants have survived -5F)
UNCOMON PLANTS
Bog rosemary Andromeda and Heather/Heath Caluna species.
Sedges and rushes especially corkscrew rush and cotton grass (sedge).Be careful some of these can get out of hand!
Gentians, great fall flowers. Patience is required to get them established.
Blue and yellow eyed grasses and smaller members of the Iris (Iridaceae) family.
Call me crazy but no bog garden would be complete without Poison sumac (yes it is in my garden). Most wonderful fall color, but don’t touch!
Orchids
Cypripedium or lady’s Slippers, C. acaule (pink) for the bog garden, C. reginae (showy), and C. candidum (white) for the "Fen" and C. pubescens (Yellow) and it’s relatives for a partly sunny spot in the Perennial bed.
Fall blooming Spiranthes or Lady’s Tresses, Small, fragrant, and a great companion to fringed gentian. These self seed in the bog!
Platanthera species, the fringed orchids, especially P. ciliaris (yellow) and blephariglottis (white). There is also P. psycodes (purple) but it is NOT an easy plant to grow!
Calopogon tuberosa, the grass pink. Showy and easy, Epipactis gigantea, giant hellborine, great if you can find a source, Dactylorhiza spp. (European) a good garden candidate, and Bletilla spp. A great garden subject needing no special care.
Sources

See the web sites for the above at www.orchidmall.com click on sources!
If you have questions feel free to contact me at: fbess7600@msn.com.