So the material i use is wax canvas tarpaulin. You can buy it on amazon. But please note that the colour may come off on clothing, so if your making a plant sack please do it naked! :)
Roughly measure the pot you want to make a sack for.
Then measure the size you need, so height is double your pot size and width is double plus one. So my pot is 6in X 5in so the size i am measuring is 12in X 11in.
Pin along the edges so they do not move when you start sewing.
Sew along each edge.
Stand the sack upside down and fold over the corners really roughly but about 3 inches long.
Mark out with a chalk pencil on the fold.
Sew along the line you have just marked out.
Then cut the triangle shape off.
Then repeat on the other side.
Turn your plant sack the right way round.
Then roll down the top of your sack to the desired height size.
Add your plant
All done. I put a saucer at the bottom of the sack to collect water. You can make these pot sacks from any material just as long as its stiff enough. Like i mentioned before the colour does come off so make sure you test where you want your plant sack to go.
All images captured by Essex wedding photographer Craig :)