What about using trellis on the bottom of the deck using pin hinges to make them removable and use the space for storage if needed. It would really help define the space. I'd put a weed barrier down under the deck too. I don't know much about types of plants that would work well for your climate though. Be careful with trees planted too close to the foundation, the roots could cause damage.

Would you consider adding an arbor/trellis over the deck? If that's not in your budget, then a table set with a shade umbrella. Smaller sized fast growing deciduous trees at the side and in front could also work, such as a pair of Cercis canadensis or Lagerstroemia indica. Some clumping bamboos could also work, but would prefer some irrigation to grow more quickly and lushly. A flowering vine across the front railing such as a climbing rose, star jasmine or passion vine would also make it more inviting.

Nothing cools like a tree, or some other significant mass of foliage overhead. It seems to function not just as shade, but as a reservior of cool air. You seem to have quite an orchard there, but obviously not located quite right for the deck.

You can certainly plant some trees near the deck; maybe some that are fast growing and some that grow slower, so you can cut down the fast growers as the slow growers fill in. Of course tree canopy takes some time to develop, and as such it can be faster to build a pergola over the deck and grow something fast on it, like a kiwi or virginia creeper or something.

But I can't help but notice that the deck doesn't run precisely the length of the house; in fact, from here it seems a bit small for the size of the house. Obviously it's convenient for the door. But from the door, it runs away from the trees, not toward them. I can't quite tell how far away the trees are.

So before you plant trees and invest 5 years waiting for shade, or invest $ and time in building a pergola, I would suggest you step back and ask yourself whether this is the deck of your dreams, or whether the deck could be better situated. Do the trees shade an area where you could build a deck? Is a raised deck the best thing, or would it be better to have a ground level patio reached by stairs from the door? Or a bit of both; a small porch with a patio below, located near the existing trees, if the shade they cast is in the right direction?

You could put a lot of energy into shading this deck, when it might be easier to put a better deck where the shade already is, or at least shading a structure that is really right for the house.

KarinL