I'm guessing it depends on the quality of the sail you purchase. We installed one for a client this spring that we purchased via the actual ShadeSail website (middle price range, stock item) and it looks and functions great. I'd recommend talking to the tech support folks where you purchase the sail (which probably rules out Amazon) about the tree attachment. Pine's a softwood and with the amount of tension the sails are under, I'd worry about a screw eye popping out spectacularly. If you read the install instructions they specifically say a 6x6 post will not withstand the forces, so you know they're pretty intense.

Thanks for your responses. After posting my question, I found sites with information for DIY installation, and I think maybe we are not ready to do that without a bit more prep and information. We're going to just hang some patio shades for the moment and take more time to think about the options. I think the sails are a very good idea, but I guess before make a permanent installation, I should have a better plan. Thanks everyone. Valerie

Wow! You might get better answers in the deck forum. We have one that we got from ecanopy.com, but summer has not yet descended, so we haven't tried it yet. Ours is a square shape and we intend to use it to block the late West setting sun from our patio. We got this one. They have others. I think there are many manufacturers. It pays to read reviews. I have to admit, I won this one. It might or might not be the best, but we haven't had a chance to try it.

The manufacturer can tell you what size poles/anchors are needed for what size sails. A word of warning though about the triangular shade sails. Go much larger than the shade you need. As the sail is stretched the sides suck in so that you end up trying to make shade out of a string bikini. Unless they are pretty huge, I find them inadequate for providing much shade. On top of that, many of them are made of fabric that is knit or woven with an open structure which allows some light to filter through. Too much light.