Quercus suber, Cork Oak, would be nice. They are fast for Oaks. Quercus ilex. Olives are classic. Aleppo pine. Laurus noblis (Bay). Choose quality over "fast growing". "Fast growing" means often weedy and eventually a pest.

and do understand.. that drought RESISTANT or not... new plantings need a year or two .. at least.. of PROPER WATERING ...

mostly because you disturb the root mass upon planting ..

ken

Thanks, people! Cork oak looks great. I love Laurus n., but it's so slow growing.In the place I'm thinking of , "weedy and eventually a pest" could actually be a plus, since one of the jobs for the trees would be to stand up to the uber-weedy,uber-pesty broom.Fast-growing IS kind of important,because I want to start shading this area ASAP,to make it unhospitable to the beetles and the broom (this latter might still grow in shade but if it doesn't flower that's already a big plus). What's more, a lot of the area I have in mind isn't even seen very much from the main garden! I'll be putting in some cypresses, but don't want a monoculture thing. I'm even thinking of trying a bamboo grove! and I already put in a Leylandii, so you can see I'm pretty unscrupulous...but I certainly DON'T want just those homely Leylandiis. I'll look up Aleppo pine and Q.ilex,but I'm afraid that olives wouldn't grow tall enough,plus they have a kind of airy habit, and I would like deep shade and hopefully the deep green colour...bart

Chestnut is drought tolerant with a nice green color, fast growing and native.

Thanks, huggorm,but I guess I'd like evergreen stuff if possible. During the heat and drought of summer,it looks so squalid and barren in that area; it would be so nice to have some deep green evergreens providing shade and at least the illusion of cool. Ceratonia siliqua seems so appealing because it is deep green in colour,evergreen, and what's more supposedly actually LIKES rocky soil. My only concern with it would be cold-hardiness, since on Internet I read that for the most part it is considered as being only hardy in zones 9 and 10, and usually my area is estimated as being closer to a zone 8...bart

Bamboo is very thirsty.

Something like Prunus laurocerasus, maybe. It's from the eastern Mediterranean. Hopefully not invasive in your area. It is fast and has the dark green you like.

You don't want to replace one invasive (the broom) with another.

This post was edited by hoovb on Wed, Mar 5, 14 at 15:20

Bay is not actually that slow growing once it gets started. Prunus lusitanica is dense, green and pretty hardy. Also Arbutus unedo - although that's not massively fast. The classic is Pinus pinea, stone pine.

Texas Persimmon (Diospyros texana) is extremely drought-tolerant - but slow-growing because it is high-quality hardwood. As logic would dictate, weak softwoods usually grow faster and hardwoods slower...
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Goldenball Leadtree (Leucaena retusa) is a gorgeous little ornamental tree that is also very drought-tolerant and used to rocky soil. It does need some sheltering from the wind though, since its wood is brittle. So, I might speculate that it grows faster...but not sure?
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Crape Myrtles grow fast and are very heat & drought-tolerant.

Twilight Crape Myrtle
The darkest purple on a crape myrtle!
Low maintenance
Highly drought tolerant
http://www.fast-growing-trees.com/Twilight-Crape-Myrtle.htm

Growing Zones: 7-9
Mature Height: 20-25 ft.
Mature Width: 10-20 ft
Growth/Year: 3-5 ft.
Sunlight: Full - Partial
Soil Conditions: Adaptable
Drought Tolerance: Highly drought tolerant
http://www.examiner.com/article/top-5-favorite-crape-myrtles
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Moringa seems too good to be true: a fast-growing, drought-tolerant tree whose leaves, flowers, pods and seeds are not only edible but also highly nutritious. Called malongay by some gardeners, the plant (botanical name Moringa oleifera) has more potassium than bananas, more protein than sardines, more beta carotene than carrots. Seed cake, the residue after oil is extracted, can be used for water purification. Some also believe that moringa may help to control hypertension, keep glucose levels in check, fight bacteria and parasites and reduce inflammation. The seeds can have a Vi@gra-like effect, according to some. More important to gardeners (well, most gardeners), moringa is a nitrogen-fixer in the soil.
http://latimesblogs.latimes.com/home_blog/2011/11/moringa.html

The only catch is that Moringa is not cold-hardy, and so will die off in freezes, but grow back in Spring like an annual crop tree.
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Texas Sage does best in dry heat.

Texas Sage is one of our most popular native plants, a medium sized shrub with several varieties to choose from including compact varieties. Texas Sage has soft silver to gray foliage with a beautiful display of long lasting lavender to purple blooms from summer into fall.
Texas Sage thrives in full sun and well drained alkaline soil.
http://plant-shed.com/beat-the-heat-with-texas-sage/
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Rosemary hedges also seem to do well in dry heat..

Rosemary is a woody-stemmed plant with needle-like leaves that can commonly reach 3 feet in height, eventually stretching to 5 feet in warmer climates unless clipped. In zone 8 and farther south, rosemary makes a good evergreen hedge
http://bonnieplants.com/growing/growing-rosemary/
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Perhaps you could plant a mix of these? Pioneer trees could crowd out some of the weeds now, while allowing time for more mature scrub and climax species to establish themselves in the meantime..

Here is a link that might be useful: Favorite underused trees

This post was edited by blakrab on Thu, Mar 6, 14 at 13:59

Arizona Cypress are drought resistant and somewhat more disease resistant than Italian Cypress. Color is typically a blue-gray-green. It is a fairly fast growing tree. Carolina Sapphire is a cultivar that is often grown for Christmas trees in the US.
Eastern Red Cedar might also fit the bill. (J. virginia). Both will reach 30-50' and are drought/heat resistant. Both of these trees should be suitable for a Zone 8 area with 24-36" of rainfall. Arizona Cypress can survive on less and Eastern Red Cedar can handle more. Not sure how available these would be where you are.
There are also several pines that may be able to live where you are. What is your soil pH and annual rainfall?
Afghan Pine comes to mind also. It has done well here in hot dry areas with under 24" rainfall and good drainage.

I would avoid planting any cedar or juniper. They are invasive, can suck up water from other trees, are prone to forest fires and cause annual CEDAR FEVER (horrible pollen allergies)!!!!
http://baledger.com/n2brokenarrow/cedar-fever-illness-at-record-levels/article_4e9b85c4-6a3c-11e2-a868-0019bb2963f4.html

Here is a link that might be useful: Eastern Red Cedar Menace

I'm so excited, thank you all for all these suggestions! Now I've got to start looking them all up, and see which ones I can find for sale here in Italy.
I was in fact thinking of that idea of mixing some real fast-growing, but possible slightly "junky" trees with slower-growing, higher quality ones. I really do have so much space,and I want a sort of wild, woods-like effect.The soil down in that area is really, really rocky and dry; even after all the rain we've had ! Of course I'll improve it as much as possible in the planting holes, and will try to add organic debris, etc. to the surface, but the bottom line is that whatever I put down there has got to be able to handle some pretty tough conditions. I really may go ahead and try at least one carob ; thanks to a poster from Arizona,I see that their record low temperatures are more or less what ours are here. Defintely Q. ilex!!!probably more than one of them!!! I'm off to start Googling; you people are great! bart

Carob trees sound like a great suggestion, but are listed as hardy in zones 9-11, similar to Mission Olive trees..
http://homeguides.sfgate.com/grow-carob-trees-pods-35719.html

You can also add lots of wood mulch and leaves (like natural forest floor litter) to preserve moisture.
http://www.youtube.com/watch?v=ji9XL4LXosE

You can get free wood chips from many tree service companies.

But if you do, I would be sure to mix the wood with nitrogen sources like coffee grounds or clean urine since it sequesters nitrogen as it decomposes.
http://www.stumpbusters.co.uk/chippings-mulch/4578451634

You can also get free bags of coffee grounds from Starbucks if you call them in the morning to keep them separate for you to pick up later that evening.

Here is a link that might be useful: Olea europaea

Good luck. I spend my life trying to get trees to grow out in the sunny garden. In fact I want to hear what works for you.
It's amazing how slowly unirrigated trees grow in a dry summer climate. We have a good depth of very compact clay, poor in organic material; I don't know how it would compare with your rocky soil. What have done best for us are the Italian cypresses, which are very good, and Italian pines (Pinus pinea). These take hold immediately and begin to grow, especially the cypresses. You could mix in some of the non-columnar Italian cypresses for a greater variety of forms. WARNING: both cypresses and pines need to have snow shaken off them after a heavy snowfall when they're young, or the pines will bow to the ground while the columnar cypresses will lose their shapely outline. I agree that bay laurel grows fast where it's happy and is handsome, however in its early life it appears to like some shade and can be hard to start in full sun. Arizona cypresses grow well but in my opinion are rather ugly trees, though they do look their best if left to grow as nature meant them to, not pruned or limbed up. They're common around here; you shouldn't have trouble finding them. I would look into whether cork oaks are hardy in your area. Holm oak, Q. ilex, will be hardy and is handsome; I don't know whether it's a quick grower: we just started some from acorns collected a year and a half ago. I'll put in a vote for olives too.
I've had surprising luck with yew, Taxus baccata, even in sun, and it will grow, not fast, but perhaps faster than you would expect. If you're interested do look into T. baccata, not the hybrids. Other shrubby evergreens include that sure thing rosemary, box, the native Buxus sempervirens, (which can after a long time get quite large), and Viburnum tinus, which I don't love but is I think native to your parts and looks quite good as part of a mix of evergreens. I have doubts about English laurel, Prunus laurocerasus. It seems to prefer some shade, but quite a few of these plants I've listed do too. Common small-leaved privet is one of the toughest shrubs of all. And there's the native tree-shrub Pistachio lentiscus, a tough plant, I don't know whether of rapid growth.
I think nurse plants came up in this discussion. Trees love to grow with some protection from sun and wind when they're small, and with the organic detritus from an established plant. Your broom might be helpful in getting more satisfactory plants started.
True cedars, of the genus Cedrus (Eastern Red Cedar is actually a juniper) are drought tolerant and as magnificent a tree as can well be asked for. Unfortunately in my experience they're slow growing, and eventually they get huge. But I had to mention them.
Melissa

Well, I went down there the other day and put up some netting to help protect the Leylandii in case animals like to eat it, and to begin to test my idea of screening the beetles out of my rose garden; this will help me to decide where to place the first trees, eventually. The broom may help getting trees started-if I saw it all down and use the branches to start building up some organic matter, that is! A long and hard job...I started looking up some of the plants people have mentioned ; I'm afraid Moringa is out because it's not available here in Italy. Melissa, I didn't realize that there were non-columnar cypresses; have to check that out!BTW 5 of the 6 "Totem" cypresses that I put in in the fall of 2012 seem to be doing very well, and have grown quite a bit; one instead keeps having health problems, so I moved it to a more open,airy spot to see if it will improve. I may well try a couple of those pines; I was under the impression for some reason that they needed more water, but from what I'm reading here, that is not true. In any case, I found a site that offers baby trees in "alveoli forestali" ,so they are very young and inexpensive, and supposedly establish much more quickly and easily than do larger plants,and so paradoxically can wind up actually growing faster in the long run! In any case, the low prices will permit me to do some experimenting. The carob tree is not available in alveolo, but the smaller potted one is only 11 euros, so if it didn't work, it's not like I'd be losing a fortune (they also offer Jacarandas, which also are supposedly hardy "only in zones 9 and 10" but look to be SO beautiful, and experimenting only would cost me 6 euros,so that's happening...) I am definitely going to put in some cedars ; both the Himalayan and the Libani ones are SO magnificent,but they will be going in a spot where they will be highly visible; far too splendid to be used as a mere bug screen!
It really might be a good idea to invest in some other Leylandiis as a nurse crop...and plan on cutting my rose orders down to the bone in the year that I actually get started on this project, so I can use all my harvested water in getting the trees started...lots to think about here...bart

Just a note on Leyland Cypress. From the ones we have planted, they either seem to be growing or dying. They do not have the ability to live thru the hot dry summers of Waco, Tx. unless they have a lot of water. They also seem to lack disease/insect resistance. We have switched to Notabilis Cypress as a replacement. Still waiting to see how they do.

Incidentally to second Melissa's advice, I have one wild Italian Cypress (non-columar) and it is growing well and is a beautiful tree.

I remember seeing common (non-columnar) Italian cypresses interplanted with the columnar kind in Tuscany. They have a taller than wide, broadly columnar form, but without the verticality of the fastigate varieties. As scotjute says, they're beautiful.
I glad to meet another fan of cedars: I adore them! There are also the Atlas cedars: similar to cedars of Lebanon, but somewhat "leaner" in habit--I don't know the right word to describe this extremely handsome tree--these include the blue forms, which are the most usual in commerce.
Leyland cypresses grow well here and if left unpruned turn into handsome trees, but our soil isn't dry. For nurse plants I think you need something deciduous. Evergreen trees and shrubs offer too much competition, whereas deciduous, deep-rooted shrubs, like roses and hazelnuts, always end up with tree seedlings sprouting at their base: doesn't this happen in your garden? That's why I was thinking the broom might be put to use, if it doesn't have a network of roots at the surface--and you could prune it as much as you wanted--to start baby trees under its canopy. But I don't know broom well and don't know whether this is a workable idea.
I buy a lot of liner-sized trees and shrubs, too, and have had good luck with them.
Melissa

Melissa, broom is a pain in the neck. I used to love seeing it by the roadsides driving through the Italian landscape; so bright, so perfumed! But I think that is the only good context for it, in a way. It would be OK where it is on my property, if it didn't attract those effing beetles so wildly; in fact, IMO, the beetles exist precisely to keep the broom from taking over the entire world, since they suck the flowers and render them infertile. But the beetles are engineered to be wildly attracted to the colour yelow; that is, the stamens of ALL flowers,and due to the geography (or morphology???) of my land (sharply sloping down from the rose garden into the broom field and below that, oak woods,with a south-west orientation),having broom down there is like rolling out the red carpet for the beetles (well, the yellow carpet). Broom has strong, fibrous tap roots that can push their way through/ between rocks, etc. I think the only way I can do anything with this area is by hacking up the ground with my pick; I can't see just planting baby trees amongst that thuggish broom and hoping them to survive.Also, I'd have to water the babies in their first year, and I think the broom would just flourish all the more.
Probably I'll try a mix of things and see what works best,but it will be necessary to work the soil before I plant anything. I probably should saw down all the broom in the area I wish to start cultivating, and maybe put black plastic bags over the stumps of the ones that are too deep rooted to dig up; for shade it might be better to rig up something artificial. I don't think your land was as abused as mine was; this area in question has been so badly eroded; I have to hunt out spots where it will be possible to dig down deep enough to start stuff. The rose garden area was similar when I started about 15 years ago,but I am not going to lug all this heavy clay, etc. all the way down there. To plant the first Leylandii I prepared an area,digging out rocks, putting in organic matter and kitty litter, etc. I'll certainly be watering it in it's first year at least! but the thing about Leylandii is that it was cheap; it's as tall as me and cost me all of 13 euros. So, if with some effort I can get it to establish,I might have a nice start.The thing is, even on the subject of drought resistance, people's experiences and opinions vary greatly with ALL plants, as far as I can see. To me,for example, roses are very drought-resistant once established, but many, many people heartily disagree with this opinion. So I will see what this Leylandii does before I make any decisions. Criteria for a nurse crop would have to be : economic ,(not to say, cheap) and fast-growing. But even for that, I will absolutely have to work on that soil ; as it is now, nothing new can start growing there, I think,except baby broom and maybe brambles (if they manage to compete with the broom)...bart