All depends upon your light intensity. I have a plastic house covered in standard horticultural UV protected poly. Over the summer months I add a cover of 30% green shade cloth to the roof area, & that is just enough to keep the broms from burning under the summer sun, also helps to keep the heat down a little. 30% green or 50% white seems to be the best shade cloth over summer for our conditions.
Check with local growers to see what % shade cloth they use / recommend.
Cheers, Andrew.

Hi jpt41,

Firstly welcome to our friendly forum, it's great to see another new member joining us for the sharing of information on the growing of these wonderful plants.

Without knowing the available light in your area, it's difficult to accurately answer your question.

To add to what Andrew says I would also mention that when doing an assessment of your available light you also need to take into account other factors such as shade cast from nearby trees or buildings in the adjacent area as well as the reflected light from bright surfaces such as light painted walls or reflection off water from a pool. They all have a bearing on the degree of available light and should be put into the equation when assessing the light.

All the best, Nev.

I live in Illinois. I have a pretty open area, and hope to get sun all day. Leaning towards 40% shade cloth

Hi jpt41, I have a small glasshouse with the roof covered in green 30% (approx) shade cloth, and the broms I have, which are mostly of the more sun-hardy type do very well in there. I would caution that when I moved them into the glasshouse initially some of them got scorched because I underestimated how hot and dry it could get in there really quickly, so I actually ended up having to leave the door, window and roof vents cranked open all the way open plus I took a pane of glass out at the opposite end to the door to create a little blow-through draft. They still need to be watered about twice as often as the outside plants do, particularly those in the smaller size pots, which I find can dry out in a single day sometimes. This is during southern hemisphere summer.

Here we have to remove any cover that doesn't allow hot air to escape. Temps in summer reach 100F frequently. We basically turn the greenhouses to shadehouses. It also allows rain water to reach the plants and there isn't anything that replaces good rain water on a brom. Occasionally we have to put the tops back on if we have an unusual heavy rainy season.

This was covered in a previous posting some time ago ,you have to take in account the reflected light inside your building ,so if its covered with black or green shade cloth the reflected light inside is lower than if its covered in white or other pale colours , even if they are all the same percentage ,so 70% white is about equal to 50 % green or black ,so think about it carefully ,also if you cover 50% with 50% this gives 75 % block out ,not 100% Ok ? trust this helps a bit ,
Jack