How good of you to take on this task! Do you have the kids help? (that can be fun too, to run it as an after school activity.) If there are flat rocks in your area, you could collect some (or alternatively keep an eye out on Craigslist for free used bricks) and use them set hozontally along the edge of the paving as deep as seems necessary (sort of widening the paving.) Leave a couple inches of spacing between the rocks and plant between the rocks with plants that can crawl onto them. That way there would be a sort of transition zone of plants that would survive being walked on since the roots would be protected, but also give a bit of warning to the kids that they were off the standard paving. The rocks or bricks will keep the plow from dropping down into the dirt and uprooting the plants and being flat shouldn't pose too much of a problem for the plow (or at least that's my experience since the plow went right over my flat brick edging a few years.) Wooly thyme doesn't seem to flower much in my garden, so might work. Some of the shorter Carex (sedges) may work, especially variegated ones like 'Ice Dance.' Astilbe chinensis 'Pumila' grows low and spreads, but flowers in August and doesn't seem to draw bees. Lady's mantle has such subtle flowers that no one will probably notice them, and has both a larger variety and a smaller one. You could also use some shrubby low groundcovers like Paxistma canbyi (no flowers usually), cranberry (tiny flowers), bearberry (Arctostaphylos) or one of the low growing winter heaths or heathers if your soil is a bit acidic. Many heathers have colorful foliage. Just check the flowering time of your particular cultivar and be sure it is during the summer. The shrubby plants you would have to plant back from the sidewalk far enough that the plow and kids won't mangle the center of growth and so that it won't grow onto the sidewalk. I don't know the salt tolerance of most of these since I don't salt the walk, but I do know that heaths and heathers seem to be pretty salt tolerant. As far as the budget . . . Once you decide on your groundcover, if it is one of the more common ones, you can check with the principal about sending home a request for donations of that type of plant. S/he may be supportive of this.

Thanks again for all of the suggestions!! Bulbs will make my have list, if I can find them cheaply. I am envisioning that most people will love the project and one or two will destroy it - so I'm doing it on the cheap. If the project survives, I'll add some more cash to the deal. I tried to eliminate water loving plants, excessively poisonous ones and sun lovers. Here's my list: If you take the time to read through it, please comment if any are invasive in zone 5. THANKS AGAIN ALL - Agastache Lavender Haze Anthemis tinctoria Golden marguerite Aquilegia Columbine Aquilegia Royal Purple Artemisia vulgaris Oriental Lime Lt Asperula Blue Woodruff Astrantia Masterwort Autumn Fern Brilliant Baptisia Australis Blue False Indigo Begonia Go Go Yellow Bergenia Winter Glow Bergenia red edge leaves Bergenia Redstart Butterfly Flower Angels Wings Calendula Clematis Mongolian Bells Coleus Giant Lime Light Coleus Giant Palisandra - Velvet Black Coleus Wizard Sunset Coreopsis Digitalis Summer King Foxglove Dryopteris Autumn Fern Echinacea Gaillardia Geranium Ripple Mixed Gloriosa superba Glory Lily Heuchera Coral Bells mix Hosta Earth Angel Hosta Frances Williams Inula orientalis Elecampagne Lamium macula Lemon Frost Ligulara Leopard Plant Lobelia Siphiliti Great Blue Lobelia Lychnis Orange Gnome Michauxia tchihatchewii Michauxia Milkweed Pink/Red Mimulus Puniceus Red Monkey Flower Mirabilis jalapa Marvel of Peru Nepeta Blue Infinity Catmint Nicotiana Only the Lonely Nicotiana Fragrant Cloud Nigella Pachysandra Green Sheen Papaver Checkers Penstemon Pikes Peak Purple Platycodon balloon flower Primrose Oxlip Primula Veris Cowslip Ruellia humilis Wild Petunia Salvia Evolution Sedum Autumn Joy Sedum Gold Moss Tagetes African marigolds Tagetes French marigolds Thalictrum Yellow Meadow Rue Thalictrum Columbine Meadow Rue Thalictrum Adiantifolium Torenia Clown Burgundy Tricyrtis toad lily Viola Brush Strokes Viola Labrador Showy Stonecrop Rose Campion Happy Gardening - Deb

Probably the easiest to find milkweed seeds are common (A. syriaca), swamp (A. incarnata), butterflyweed (A. tuberosa), and tropical (A. curassavica). The tropical is not native or hardy up north and grown as an annual, but it is readily available and easy to grow. I'm sure if you posted on the seed exchange that you were looking for a large amount of milkweed seed you would get several offers for postage only or maybe even free since it is for a school project. Gardeners are pretty generous I have found especially if you are teaching kids to get involved with nature. Be sure to educate the kids and any plant recipients about the nature of milkweed and that the "milk" inside is an irritant that can cause eye damage if not handled properly. Some varieties like the common milkweed can exude lots of milk when cut while others like butterfly weed are much less drippy. The common is an excellent food source as it gets tall with quite large leaves and spreads a lot, but it may not be wanted in small gardens due to the aggressive nature. It is better for wilder areas. Swamp milkweed is smaller and less aggressive and likes moister soil obviously. Butterfly weed is even smaller and bushier and tolerates dry soil and has a large taproot to seek out moisture. I have had cats on all these kinds although the butterfly weed is less used when other juicier types are available. The butterfly weed is popular when first planted when the leaves are young and tender. In the pic below you can see I had my very first cats on tiny freshly planted seedlings of butterfly weed that I was shocked they even found. I agree with KC that you could try other butterfly host and nectar plants as well for some variety. Hosts for black swallowtails are readily available too. That butterfly life cycle book is excellent. While it doesn't cover all the butterflies it covers most of the common ones with great pictures that are very kid friendly. Most of the plants are easy to start using the wintersowing method. And easy option would be to sow seeds in extra large plastic drink cups, quart size yogurt tubs, or similar containers. The open tops make them easy to sow in, transport, gift, and plant out from. Below is a link the wintersowing FAQ if you aren't familiar with it. Here is a link that might be useful: Wintersowing FAQ

I'm a school district construction manager, and often am faced with a situation like this (and yes, no money, and it's only going to get worse). Gophers are a big problem, looks like if you could develop a meat gopher you could feed the world. Unless they are controlled they will shred any planting you do (the district might have an IPM guy on staff). The district also doesn't do well with anything except flat grass you can mow with a tractor; planting beds get weedy and shrubs die off or get trampeled. It's too big for any rubbel mural (which also will be window ammunition). You're better off spending that time and energy doing a fundraiser to install irrigation and bermuda grass. Do not plan on volunteers for maintenance, people lose interest and it falls back on the district, so they need to have buy-in.