I love chair planters. This chair was given to me by my Mother-In-Law. It's probably 100 years old. Once I cleaned off the dirt, I realized the navy blue paint was in great shape for it's age, so all I did was dry brush some light colored paint over the blue and add a couple coats of polyurethane. It lasted in my garden for about three years before it fell apart.
I used a wire basket with a coconut liner to hold the soil for the plants. You can find these baskets inexpensively at dollar stores or discount chain and big box stores. Just remove the chain hanger, and then staple it to the underside of the chair as shown in these pictures.
I filled it to over flowing with various annuals, and it looked great right up until frost. I also added a frog pot sitter on the top. This planter was featured on ThriftyFun.com and at Birds & Blooms.
To the left is another way to make a chair planter. The opening in this chair was smaller, so all I did was push in a willow basket. I lined the bottom of the basket with newspaper to keep the soil from falling out.
The above chair is metal so I made a cone out of chicken wire and wrapped the edges of the wire around the edge of the chair where the seat once went. Once finished with step 1, I pressed spaghnum moss into all the chicken wire holes so that it would hold the soil. I imagine this chair will last forever and will just need a fresh coat of paint from time to time and new moss as the old decomposes or gets thin from wear.
If you click on any of the pictures, you can see them in a larger form.