if it's going out in the garden, the obvious one to me is
"you made your bed- now PLANT it!"

If it does not need to be about plants, you can quote a line from a favorite book, movie, poem or my favorite the bible.

I did a flower bed and I made some "bricks" you know the kind you pour then stick little letters into? Well its not as easy as it looks but anyhow my bricks say... Sleeping with the Anenome. I planted fall and spring Anenomes in the bed. It didn't turn out that great this spring...the way I thought it would but I am sure next year will be nicer. Here's a picture..thats my cat Wyatt modeling for the photo(-:
{{gwi:143010}} I also like the saying Lifes a Garden...Dig In

Love the saying! And, I must also say "I love Wyatt!" IMO, Cats, dogs, and I even saw someone with a pet bunny ARE the most wonderful garden decor!"
Jeanette from Mississippi

my favorite quotes(not gardening, though...):
"We can judge the heart of a man by his treatment of animals." ~ Immanual Kant
"The purity of a person's heart can be quickly measured by how they regard animals" ~ Anonymous
"Who can believe that there is no soul behind those luminous eyes!" ~ Theophile

Try going to: http://www.gaygardener.com/quotes.phtml
for garden sayings. You can also google "inspirations" and many things will come up.

Here is a great site for all sorts of sayings including gardening: http://www.quotegarden.com/index.html

I had a case of reneculas and anenomes once, but it's cleared up now. LOL I'm going to have fun going through these suggestions. Thanks for the question, as we'll all enjoy the ideas!