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

Jean - I hope you meant the 25th (the Wake Forest market is only on Saturdays). Lets aim for Saturday Sept 1st. This next weekend is a big grilling festival at the market and I need to haul as many sellable plants as possible to make up for the lackluster sales these past couple of hot and dry marketdays. I will also go through all my various stashes of plants to find more goodies by Fall Swap. And next spring I should have even more after sowing seeds all winter. I have Rue. But the caterpillars on it are eating it down to the nub so I doubt I will get seeds. I plan on finding some seed somewhere and growing a bunch of it, so at some point I will have some available. I do have some parsley potted up and some Agastache (Hyssop). If you find any of the annual butterfly weed (Asclepias currasavica)(sp?), I have been able to over winter the roots and got bigger plants the next spring. I simply dig them up after first frost and pot them up and store them out of the way. They are easy from seed also. Pentas are a great nectar plant and they are easy from cuttings but they won't overwinter outside. Good luck

Gina and nanduta, Go to this thread (link below) and read some of the Frequently Asked Questions. I'm not trying to be rude. Both of you need to enable messaging so that people can message you directly and that's how we share our addresses and information. We don't want you to put your address out here for the world to see. We hope there aren't any stalkers, but we try to keep information between individuals. Gina, look on the Exchange Thread, Seed Exchange. That will have the Newbie Seed Project and you can click on the name of the thread starter. Then click on "Message" and you can ask about free seeds or seeds for postage. She does a wonderful job. Heidi http://forums2.gardenweb.com/discussions/3371179/attention-newbies-please-read?n=33

Is this just gardening for fun, or is the school making a commitment to the garden as an ongoing project? Does it tie into curriculum, and will there be education or experimentation involved? If this is for high school students, hopefully you can get some help from local agricultural educators, the UC Extension service, and your local Master Gardeners. If seed saving would be an ongoing part of the project, there are sources that will provide both free seed, and educational materials. I have provided a link to one of the better resources, the Community Seed Resource Program. I too donate seed to support civic projects... but because fraud is so rampant on the internet, I will only mail to institutional addresses. You can reach me via PM on my member page.