Outdoor Ceremony Decorating Tips

I am looking for ideas for around the "alter" area for our wedding. There is not any structures such as gazebos, arbors, etc. In the area we are having our wedding. I have heard that you can rent these things, but I am afraid that it might get quite costly. I am looking for alternative ideas, and also some decorating ideas as far as flowers around the "alter" area too. Our wedding is in June, and I am not sure what flowers are in season at that time of the year. Any web sites that you might suggest would be much appreciated. Thanks!