I am doing something similar with a slightly younger age group, in my own home gardens. We will have a club that meets every other Saturday. Some of the things I'm thinking of including are:

reading rain gauge and compost thermometer
keeping a garden journal for sketches, notes, etc.
giving kids thier own squares in raised bed veggie area
starting plants from seeds and cuttings
having a garden scavenger hunt
collecting and identifying garden insects
cutting flowers for bouquets to take home
"taste-testing" fruits, berries, and veggies
decorating stone markers for plants
bringing compost donations and making compost
gathering and labelling seeds from garden
attending a plant swap or donating plants to comm. gardens

I'd really love more ideas about what kids have really enjoyed doing as garden projects, and how to keep them engaged. I'll look forward to seeing whatever responses you might get to this thread!

A couple ideas to add (CStrass has given you some good ones):
Make flower presses
Have a worm bin
Make dyes from plants

Here is a link that might be useful: Good Site With Lots of Activities

check out the book Kids Garden by Avery Hart and Paul Mantell. It has some neat ideas for projects in it.

Also look at "Sunflower Houses" by Sharon Lovejoy. She describes many imaginative activities for kids to do with flowers. The descrition of how to make a sunflower house is especially fun--but it takes a large chunk of the summer while you wait for the flowers to grow.
Docmom

The issue I see with this is that a 1 or 2-week camp isn't going to allow kids the chance to see things grow in any significant way. I mean, you could sprout seeds and send the kids home with seedlings in pots, but you won't be able to create and maintain and harvest a garden. So I'd focus on one-day activities. Scavenger hunts, wildflower collecting and identification, comparing different types of soil by mucking about with dirt and water (three wheelbarrows full: loamy, sandy and clayish), examining a working compost pile, a wildlife "hunt", making sunprints with a variety of foliage (you can use sunprint paper or setacolor soleil brand fabric paint), making scarecrows, building a trellis.

The one growing project that you could complete in a wee would be growing alfalfa sprouts. On Monday, give each child a teaspoon of seed, an empty jar, and elastic and a piece of fine screen (so-see-um netting or old sheer curtain fabric). Put the seed in the jar with a bit of water, use the elastic to fasten the screen over the mouth. Swill and drain by inverting the jar. Repeat the swill&drain process twice a day. After 5 days, bring a sandwich for lunch and add the alfalfa sprouts you've grown and enjoy. Kids could take their jar home on Monday, tend it morning and evening through the week, and bring it back on Friday for lunch.

Hope that gives you some ideas!

Miranda

I am going to borrow some of these great ideas. I have tried a lot of them already. Some of the most successful I have found (especially when you have the kids for a while) are those that allow hands on work, such as making a flower press or that involve obsrvation.
Another fun activity, if you have a woods or digging area near is to create a living space for a tiny "alien". The child or a couple of kids are given a designated space( one yard square is good) marked off with string. Then using what is in that space they build a shelter and gather all that a tiny person would need to live. I also did this over a several day time in a classroom in planter trays. The imagination and creativity was wonderful. After they were finished it was fun for everyone to share and discuss what was done.
For older children, there is a lot of information in the 4-H curriculum. Most is available through your extension service.

The kids can make their own 2" pots out newspaper to put their cuttings in. (Succulents are good for this, or starting seeds too.) The pots stand up quite well for weeks even during watering and can actually be planted in the ground along with the new plant in it.

There are pot presses you can buy, but if you just use a soup can (or I use a fish food can), the kids can wrap about it a 2-3" wide strip of newspaper(about 12" long), fold the bottom down and tape it, and tape the side. Then you have a pot made of newspaper. If this sounds totally confusing, and you want to know more, e-mail me and I'll try to help better.

The kids enjoy seeing the cut-off tops of carrots sprout in dishes.

You can do leaf rubbings with leaves that have prominent veins, usually on the back. Try crayon or the side of a pencil. Fig and rubber plant are good choices, big with prominent veins.

wow. fantastic suggestions! I, too, am doing a summer camp...calling it "how does your garden grow?" (ok, not very original...)It is only 1week long, mornings only, so these 1 day project ideas are great. I am planning to do a little bit of parts-of-a-plant, parts-of-a-flower,(my montessori training showing) as well as planning or designing a garden (art project) decorating (plant markers, stepping stones) garden wildlife - pests and helpers, some vegetable garden stuff, painting with cut apples, celery bottoms (they make beautiful rose-like print)etc. A really terrific book is by Edna Miller, called "MOUSEKINS LOST WOODLAND" which shows what happens when a new house is built without regard for environment, then it shows a home built with nature in mind. Nice contrast. I'm not a tree-hugger, but this story shows how a little planning will keep everyone happy!
anyway, thanks to all for the great ideas!!!!!!!

No fair, I wanna come!!! Sure, I'm 37, but it sounds like so much fun!!

I've tossed around the idea of a gardening class for our homeschool co-op group, but didn't think there was much we could do. We use a local church's buildings so I couldn't have anything permanent. There is also a Backyard Science class going on and I thought my idea would duplicate in some way.

Neesa in FL

That sounds like so much fun. I encourage you on this. I can remember when I was younger it meant so much to me when I was taught how to garden! Good luck with your class and I am sure it will be a huge success. When you are taught at a young age you learn to appreciate gardening so much more.
Good luck.

Kimberly in AL

~Dry flowers, buy white candles and either with melted wax or modge podge paint the flowers on the outside. Makes a beautiful gift for mom.
~Also, take a clear plate and put dried flowers on the back side. Talk to folks at the craft store and there is a medium you can put over tissue paper to make dried flower plates.
~Take frames and have students glue nature items to the frame. Take their photo and voila.
~Do leaf rubbings of different textures and shapes.
~Have them use items from a nature walk to make scrapbook pages for photos at the end of your program.
I have done all of the above with both boys and girls and it has been successful.