It should help. We call that a shade structure. Be sure to anchor it in case of wind.

You have an awning. I take it that it is an aluminum awning which is what I have for shade on my patio.

I personally would not recommend it for shade due to your plants will get NO sunlight. Our garden we use the green shade screen available at Lowes/Home Depot. It lets through a certain percentage of sunlight. You can buy different types of screening, some letting through more sunlight than other depending on what you need. You find it in the garden department. We attached ours to stakes in the ground and had a building to attach the other side to, allowing us to walk under it.

Patti

Patti has a good point but I still think it's better than nothing at all. You plants will soon fry, if they have not already.

If it's tall enough to walk under, as the sun moves some sun will get through. If you can replace the cloth with shade cloth, it would be better but that stuff is expensive.

Good luck in any event. Hope your plants make it through the summer.

It isn't aluminum. It is like the tents that they sell now that are very tall (you usually see them in the patio isle). The cloth over the top looks like it is canvas of some sort. It is 15'x15' and about 8 feet tall.

Are the sides open or screened in? If the sides allow light in and are not solid it might be okay. If it gets enough slanted morning sun coming in, and enough slanted afternoon sun it would prob be enough while keeping the direct overhead afternoon sun off. If the sides are solid -could they be rolled up?
I put up a shade structure up using the shade cloth at lowes also. It is just about perfect as far as letting the light in (The leaves don't fry and everything still flowers).
I was gonna use the gazebo tent we got but the kids sort of took it over lol. Perhaps you could try putting a tarp up on a few stakes and just sort of watch were the sun goes before taking all the effort of putting up the gazebo first?
~SJN