I researched this for an annual event we hold building fairy houses out of natural materials, and came up with plenty of info on the internet by Googling "fairies + plants" or "fairies + plants + favorites". (I'd give you my list, but just now am "locked out" of my computer as I seem to have mis-remembered by password!)

Fairies have a fondness for all things natural, but they do have some favorites. Of course, the usual: hollyhock, forget-me-not, viola, foxglove, thyme, roses, rosemary, columbine, lady's mantle, and so on, but you'll find lots more on different sites, and some even list why the fairies like them ... what "powers" they hold. Don't forget trees! Fairies are particularly fond of oak trees, but also elder, ash, holly, hawthorn, and apple.

Here's a site to get you started:
http://www.gardenfairy.com/fairygarden/fairylore.htm

You and your nieces may also enjoy this site - it has some beautifully drawn coloring pages you may download for free:
http://www.pheemcfaddell.com/index.html

If you haven't already done so, try to find a copy of Tracy Kane's book "Fairy Houses" to read to your nieces. Tracy has now written several books in this series, and they are all lovely and very inspiring. Your nieces will, no doubt, be eager to get outside to build fairy houses of their own! Just remember the fairy building codes: don't pick or otherwise harm any living plants and nothing artificial - although they do like things that shine or sparkle ... a crystal or piece of "sea glass" will do if you don't have a gold nugget handy ;-)

I was just amazed at the delightful structures the children and their parents built at our park, all without glue, wire or any other fasteners. Of course, nature had its way and they all tumbled down in time, but the fairies enjoyed them in the meantime. At the conclusion of the program, I went around with a bowl of "fairy food": birdseed and different colored split peas and lentils, which we put into seed pod bowls.

You may want to consider including plants that have flowers, seeds, pods, cones, stalks, etc. that will make good building materials for your nieces to work with.

As to what I would include, if it were up to me ... I would include the plants I particularly like, native plants, and plants that attract birds, butterflies and beneficial insects, providing them with food, shelter and nesting places - that would mean a lot to the fairies.

Strings of lights?, they make solar LED ones now so no need for an electrical outlet. If you are incorporating an arbor or alle', weave the lights down thru the "tunnel".

I'm all for decorating a garden in order to transform it to the magical realm. For example hang festive lanterns on branches.

Also -a fairy garden isn't complete without a fairy house and toad stools. Make the fairy house out of twigs and thatch, pebbles and moss.

Also - in case this gets into a party scene.. A Maypole,ribbons, and little girls with little crowns of flowers?

And for games --- make a grid of say 4 or 9 squares with bamboo. Hang toys and candies on this grid. Now elevate the bamboo onto a branch with a long rope. The idea is like that of a pinata except that its this giant grid with treasures hanging from it. you can lower it and lift it as children come running to grab their treasures. -- You don't even need a party to have this kind of fun

Moss and stumps are necessary. Carpets of little, tiny flowers. Bleeding hearts.

If you have the space, what about a large size tee pee? Make a tall wide tee pee from say 8ft stakes, using several, then plant morning glories around the base to grow up the vines and fill in. All kids like little private spaces to climb into. Then maybe a miniature fairy type garden around the tee pee.
Tammy

I love the idea of a magical garden. Most of my grands are a little older, but I have younger ones, and the three year old went through my garden fascinated with blooms and wanting to smell everything, so fragrance is important.

I have some little fairy houses that he loves too. You might consider one or more of them.

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I plan to nestle them in sweet alyssum at the foot of the roses.

kay

Four oclocks and moonvine. They bloom late in the evening. You can watch the moonvine flowers open at dusk. Takes about a minute once it starts. That's magical to me.

to me... fairies live in places with lots of moss or really-low-growing ground cover. Like thyme, etc... I'd cover a large area with that... and if possible,... have it growing in big mounds like tiny hills.
... I think plants like bluebells and crocuses are pretty magical, too. Have fun.

Hmmmm....I've never seen a fairy movie or read a fairy book. I guess I didn't live a fariy tale childhood ;) When you said magical I thought of only one plant. Love in a mist.

MeMo

Thank you all for so many wonderful ideas!

Agardenstateofmind- Such a great list and I appreciate the websites :)

Schoolhouse- Little lights would be magical.

Ianna- Great ideas and I would love to do a party with all of those fun details.

Mbravebird- That does sound fairy like :)

Tammy- A teepee would be fun.

Kay- I love your little houses. That's going to be charming.

Token- That would be magical!

Aimeekitty- Very cute and just the right size.

MeMo- Funny that you say that, because I've had this "picture" in my head of a fairy garden that is part woodland garden and part climbing old-fahioned roses twining up an arch or wall. Then the other night, I realized where I'd seen that...Snow White was on TV and I was going through channels....and there were the old-fahioned roses by the well, and five minutes later, there was the woodland part. LOL I haven't seen that in so many years, but I guess it made quite the impression on me when I was young :)

How lovely! Seems to me that any fairy garden should have a GIANT plant, no? Perhaps Allium??

I was thinking along the exact same lines as Token. Moonflower vine for sure. I am actually reading a book called, "The Moonflower Vine" by Jetta Carleton about a family that has a tradition of watching the flowers open in the evening.

Another thought is heliotrope since it moves during the day to orient its flowers toward the sun and then returns to facing east at night to be ready for sunrise.

My 6.5 year old thinks strawberries are magic since the flowers turn into strawberries. Guess that would work with lots of veggies and fruits!

Lisa

I think a fairy garden could use a little story-telling. When I was a child, my parents took me to a "fairy-tale garden" in Ludwigsburg, you had to cross over a "river" on a path of stones, and there was a frog with a golden ball in his mouth, and a candy cottage where the old witch tried to fatten up Hansel and Gretel with sweets.