If you have a pair of jeans beyond repair you can repurpose them into a gardening (or other activity) apron by cutting away everything not part of the apron.
Culinary weblog Chow.com shares the method for the transformation. Use a heavy-duty pair of scissors to cut through the front side of the pair of jeans along the bottom of the waistband until you reach the side seam. Cut down the side seam and then cut across the seat of the pants to complete the apron.
Now all you need to do is put the apron on and button it shut.