Obviously this is a mental excersize, because you'd need a pond, and a whole lot of room.
I wanted to call this a dinosaur garden, but most of these plants, were from the next era.

What might be fun in such a place?
Any height is fine.
Reccommend away.

I'm working a lot more natives into my gardens, and seeing a lot more beneficial insects, butterflies, a more interesting variety of birds, and now a hummingbird that seems to be a regular (I don't do "feeders", only attractive plants).

Don't have a large lot, but do have a koi pond with a bog set under a huge white oak, surrounded with mountain laurel, chelone, tiarella, sassafras and some other things not so native; it was too shady for the cattails. Also have redbud, passiflora, native honeysuckle, great blue lobelia, ninebark, ... oh, my, now that I start thinking about it: sweet bay magnolia, amelanchier, leucothoe, aquilegia, ginger, river birch, carex, clethra alnifolia, fothergilla, dogwood (virginiana), redosier dogwood, swamp-pink, mayapple, inkberry holly, Virginia bluebells, Solomon's seal, sweet white violet, dicentra, ferns, moss ... who am I forgetting?

Of course, it is not just what one has, but how it's put together ... and that's the part I'm working on now. But all have proven to be hardy and trouble-free (except that something has been eating holes in the leaves of the chelone and the swamp-pink requires certain conditions).

Tulip poplar is a beautiful, stately tree; it's a shame we don't see more of them around, but I understand the limbs can be somewhat weak in storms. I've heard that horsetail can become invasive and know that trumpet vines will spread like crazy (as will the passiflora incarnata) if you don't keep after it.

I understand there is (or was) a climbing fern (not far from some cypress like you mentioned) in a marshy, wooded area of a nearby county park. Meant to go searching for it in late winter/early spring, as it is evergreen, so it would have been easy to find it then. That would be a good candidate for such a garden - there's a link below with some photos and information.

How about paw-paw? Yucca? (Though I'm not fond of them - too spiky, and they look like they belong in Arizona.) Orchids! - an ancient and widespread family; there are some native to the eastern temperate regions - nodding lady's tresses (spiranthes cernua) is one I would love to have.

This could be too much fun. I look forward to seeing other recommendations. Thanks for starting this thread! (A dinosaur garden ... wouldn't children love that?)

Herds of lady's slippers. Ancient 2' tall Jack-in-the-pulpits. Venerable Solomon's seals. Dutchman's breeches. Colonies of American ginger. Trilliums!

Turtleheads along the streams. Forests of jewelweed wherever the ground is damp. And ... I'm not fond of skunk cabbage, but it does have that prehistoric wilderness look.

So too Virginia creeper (climbing all the trees ... impenetrable wilderness).

I hope we can all agree we to skip the poison ivy and sumac?

Great ideas! more More!

Oh, I can tell you there's plenty of poison sumac in Connecticut, also in areas of Ohio and Illinois where I've lived. It's here in WNC too -- they warn about it when discussing outdoor safety -- though I haven't seen any yet. I never encountered it in California that I was aware of, though we had poison oak to avoid at camp and one place we vacationed.

Here's the USDA's map for poison sumac; it's in much of the eastern half of the country, but no farther west than easternmost Texas and Minneapolis. However, I've seen two maps that disagreed on which counties in WNC it grows in. So perhaps the USDA's out of date if you've seen it in the West.
http://plants.usda.gov/java/profile?symbol=TOVE

And moss. I'm a sucker for cool moss. :-) (I ask neighbors for cool moss. They think I'm crazy. Are probably right.)

It's kind of fun to look up some evolution, while doing this. It's eye opening.
Aside from ferns and cool mosses etc., most of the plants and animals we know, developed later. Among them were flowers, bugs, trees, mammals, and all the natural interactions of modern life. Anyone have some good sites to link to?

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Mmm, How about a vernal pool by a lush mossy grotto. A few horsetails are hemmed in by rocks, with a visiting skink?

Various tree seeds are still about, say - red gum, sycamore, or beech nuts. They don't get raked up, because this corner of the yard, is a natural area.

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The seed shapes, or spent flowers from 'dirty trees' are often luscious. They have been removed from the current experiences, of the average passing kid. Our sense of the natural world, has become diminished. It's a loss to the senses, and to wonder.