I use small 4x6 photo albums to save my plant tags. They can be saved by year, color or type. The albums are plastic and can't be hurt by dampness if left outside. They are inexpensive and can be found at Wal-Mart or a dollar store.
I also use larger albums with 4x6 pockets with an area for notes. These albums are not weatherproof, but are helpful for making notes such as where or when the plant was planted.
—Carol Lundquist, North Carolina