Zech,

Use some whitewash on the roof of the greenhouse and get a fan or two inside for air circulation.

Sorry not 150 degrees, 115 degrees. :P lol ... but can they survive 115? (Possibly lower now that that is going to be done)

My cactus survive 115 if they get some shade and it does not stay there long. That was last years heat wave. It was only there a couple of days. Usually 105 - 110... It will be 109 again this weekend. Most my cactus are out in brutal sun but some of them get some shade in the afternoon or morning. My echeverias, aloes, stapeliads, and euphorbias, have more shade. These are outdoor conditions, not greenhouse conditions. Can you rig up a fan in your opening??

I really dont know where i will get a fan, and where will it connect to? My green house is like, really far from the house ... maybe solar panels? Could opening up the door work somewhat?

Is it really that hot in texas? Dang! I thought it was hot in southern california! How do you stand it?

Whitewashing it would definitely be a first step. If it only has a little window and a door, I wouldn't put anything in there unless you can get a fan going. Or, put your least liked plants in there if you must, so if they croak you won't cry too much over their loss.

Which plants do you want to put in the greenhouse?

I have a patio umbrella that I leave open during the time of year when the area where my succulents are gets too much sun for them. In the winter, I just leave it closed. This could be a "portable" option for you. You can get a cement base for the umbrella and just put them anywhere you want. Some umbrellas have a joint in them so you can tilt them at an angle too. Umbrella fabrics can provide different levels of shade as well.

If you are going to be on this property for a while, perhaps you (or your parents) would consider planting a tree, or building a lath structure to provide some shade if that is what you are looking for.

The green house is plexiglass all around, i think i should try with some ugly plants first.i was going to put succulents in there and maybe some tropicals

I have three umbrellas and they are all shading cacti :P maybe i can move the umbrella with the ones shaded by it into the green house! There is a nice silverdollar gum tree right next to it so maybe that will shade it in a few years

The testing shall commense today! I think i will stick a kalanchoe tubiflora in there

They do make shade cloth. I have 40%, which lowers the temps significantly. The disadvantage is that it needs to be on the outside of the greenhouse, and with our frequent thunderstorms tying it down means not allowing it any loose sides. This shade cloth is a mesh of woven black plastic, and the amount of shade varies with the weave. It comes in rolls of various widths.

The heat you mention won't hurt most plants from the desert, but the sun can fade things like Gasterias, Haworthias and even some desert plants. I have a Ferocactus latispinus with a withered side from sunstroke.

One final note, if you don't have a fan, you need to do something to move the air around. When I was starting out, a certain Cactus Cowboy from Wyoming told me that air movement was as important as water to a cactus. All my experiences since then have borne this out.

Dz,

There's a name with pleasant memories - Cactus Cowboy sent me plants a long time ago and generally was very encouraging to a youngish succulentist starting out in San Diego.

Zech,

I will repeat, whitewash and a fan - I would say perhaps your greenhouse needs to be resited if it's too far from the house for power. Alternatively, a 16 ga. extension cord will handle a fan's electrical draw quite well.