I'll put on my Master Gardener hat here. UV rays cause us to sunburn and they can also cause a plant to sunburn but there are other factors. A plant will burn when the leaves give off more water than they take in. This can be caused by strong wind, chemicals, UV rays, extreme heat and so forth. Plants tend to adapt to their environment so when they are moved and come under different conditions, it takes time for them to adjust. If in shade, they grow shade leaves which usually get fried when quickly moved into the sun. Excess heat will also burn plants which is my concern with this lanai during the summer. If you block the UV with this tarp while also reducing heat with the screen cloth and have the bonus of blocking strong winds, you should be in good shape.
Jim
