Best plants to improve clay soil in a Mediterranean climate?

Most of my property around my house is clay soil with degenerated granite, with a lot of bare areas. We live in a low USDA zone 9a, although I suspect my micro-climate augments that to create higher lows. The areas that are bare are mostly sloped, facing west and south west. The Summers can get very hot, and of course are dry.

I am wondering, based off of personal experience what are the best plants to grow in this condition to help improve the soil? I need plants that will either do a lot of soil building in the winter, or are perennials that take highs that potentially go up to 110 degrees F. Thank you for your input.

Will there be water access in summer?

No, I'm not planning on irrigating these during the summer.

Perhaps you could go to the nearest nature preserve and look what plants are doing well naturally? Maybe build a hugelkulture, top it with compost, and see what the winds blow in...

Hardy nitrogen fixing trees are great. I had a mimosa tree when I lived in zone 9. Really hot summers in the 115 range. I chopped that tree down tothe ground every few weeks. It made excellent mulch, shade and habitat. We have them here where I live now and we get temps down to 18f.

I would try not to let it seed down there as it could take over a bit. Seedlings are easy to get out, mature trees are not. Given they provide mulch for years on end in the growing season with management and fix nitrogen and build soil.

Some call it invasive so keep in mind.

There is one mimosa tree that the previous owners planted about six inches from our house, it was only two or three years old if I had to guess. I moved it last winter to a different location, it didn't put on much growth this past year. I am hoping it takes off. I do know that where I live they can be invasive, everyone once and a while I notice a young mimosa near the main roadside where no one would purposefully plant one. Thank you for the suggestion.

I'm thinking about growing some mesquite on the barren hillside too.

I too face tight clay soil in a similar climate. But trees seem to do OK once they are established....and the fruits get some irrigation. Beware of things that really need good drainage (based on research, pistachio, peach, and apricot are near the top of this list.....and avocado and citrus if you can grow those) These I'm planting on mounds or in small "raised beds" enclosed by 3 lengths of utility pole, so as to get them started in better drainage. I'm planting a lot of mimosa, too, and I'm trying some acacia and casuarina (don't know yet about these and our winter....it was 12 one morning last winter but there are still eucalyptus around). Mimosa isn't nearly as invasive as it is in the Southeast....the seedlings really need summer moisture to get established, so they simply can't start unless they find a moist nook. For garden crops, I'm building up with sheetmulch, mulch, compost, whatever I can get hold of.

We have Black Locust and Hackberry trees that are about seventy years old. They do great in the Central Valley. The Locust spread very easily, and the hackberry aren't that shy either, but the sprouts are easy to control with a shovel.

sheila reavill wrote:We have Black Locust and Hackberry trees that are about seventy years old. They do great in the Central Valley. The Locust spread very easily, and the hackberry aren't that shy either, but the sprouts are easy to control with a shovel.

Do you know which species of Hackberry you have growing? Also, how big would you say it is?
I am interested in both of the trees you mentioned.

I don't know which kind of Hackberry we have. It's about a hundred years old and very big (about 30 to 50 feet) and too wide around for me to fit my arms around. I heard they grow them in Texas as hedges. Our big Locust is bigger than that and scary 'cause it's old and leaning. There are tiny groves of Locust all around. I love Locust, their big, fat aromarous flowers in the spring, their tendency to cluster in convenient mini forests. The chickens love the shade and jungliness of the young ones, and they eat the leaves too. They are the only things thriving and green in the hot summers and don't mind going without any water. The goats just plain love to eat them. I really don't understand why people don't plant and cherish them all over the place.

sheila reavill wrote:I don't know which kind of Hackberry we have. It's about a hundred years old and very big (about 30 to 50 feet) and too wide around for me to fit my arms around. I heard they grow them in Texas as hedges. Our big Locust is bigger than that and scary 'cause it's old and leaning. There are tiny groves of Locust all around. I love Locust, their big, fat aromarous flowers in the spring, their tendency to cluster in convenient mini forests. The chickens love the shade and jungliness of the young ones, and they eat the leaves too. They are the only things thriving and green in the hot summers and don't mind going without any water. The goats just plain love to eat them. I really don't understand why people don't plant and cherish them all over the place.

I like your suggestions. Thank you.

I think a lot of people don't like Black Locust because it's prickly and therefore a challenge to work with/among. Some find the root sprouts invasive too. But given space and not minding the thorns, it's virtues shine. Not only does it provide forage for poultry and goats, but the flowers are good for bees and the larger trees make both excellent firewood and rot-resistant timber. I wish I had the space for it, but on my small holding I will stick with mimosa to start with.....

Thankfully I have the potential space to plant what I want...

I second the "mimosa" (I assume you mean albrizia julibrissin) which isn't really that invasive in clay, and the mesquite, and add acacia, because I'm jealous you can grow acacia well haha. Eucalyptus. As far as annual veggie type things go, I have had good luck with quinoa and lady peas (a type of southern pea) loosening unamended clay soil. It was strange though, it would loosen the soil but without changing the color really or adding much organic matter. My soil is similarly decomposed granite, although I suspect it is much more rain-leached than yours. Which means you probably have a better trace mineral balance than me, and a higher PH.

Bob Dobbs wrote:I second the "mimosa" (I assume you mean albrizia julibrissin) which isn't really that invasive in clay, and the mesquite, and add acacia, because I'm jealous you can grow acacia well haha. Eucalyptus. As far as annual veggie type things go, I have had good luck with quinoa and lady peas (a type of southern pea) loosening unamended clay soil. It was strange though, it would loosen the soil but without changing the color really or adding much organic matter. My soil is similarly decomposed granite, although I suspect it is much more rain-leached than yours. Which means you probably have a better trace mineral balance than me, and a higher PH.

Thanks for the input.

Any recommendations on specific Acacia and Eucalyptus Species?

One day my place will be awesome. I will have a wide variety of food and medicine growing here.

One critique of Eucalyptus and some Acacia species in Mediterranean climates is their high flammability. One would want to site them away from and downwind of buildings, and place more fire-resistant trees between....

Alder Burns wrote:One critique of Eucalyptus and some Acacia species in Mediterranean climates is their high flammability. One would want to site them away from and downwind of buildings, and place more fire-resistant trees between....

Thanks for bringing that up. I am in an area that is prone to fires, both natural and man caused. So, now the question is, what plants are fire resistant?

Here are some lists of fire resistant plants:

http://www.bewaterwise.com/fire02.html

http://www.landscapingnetwork.com/plants/fire-resistant.html

http://www.theodorepayne.org/plants/fire_resistant.htm

Thank you.

In general anything that is aromatic or resinous is going to be flammable.....conifers, eucalypts, and quite a few other evergreen things. Dry, tall grass is a prime problem. Deciduous trees are better, and the more moist they are kept the better. The native oaks are surprisingly resistant....the foliage must scorch before it can start to burn. Often the entire crown can scorch and brown, but dormant buds often leaf back out the following year. A drive through a burn site will provide some interesting observations.

Alder Burns wrote:In general anything that is aromatic or resinous is going to be flammable.....conifers, eucalypts, and quite a few other evergreen things. Dry, tall grass is a prime problem. Deciduous trees are better, and the more moist they are kept the better. The native oaks are surprisingly resistant....the foliage must scorch before it can start to burn. Often the entire crown can scorch and brown, but dormant buds often leaf back out the following year. A drive through a burn site will provide some interesting observations.

Makes sense.

Steve Flanagan wrote:Most of my property around my house is clay soil with degenerated granite, with a lot of bare areas.
I am wondering, based off of personal experience what are the best plants to grow in this condition to help improve the soil?

Something I read in Gaia's Garden (Toby Hemenway) inspired my current "method" to fixing my similar conditions.

He says basically that nature abhors a vacuum. If you leave a piece of "dead" landscape alone, nature itself will fill the space with whatever fills the
need from the local environment. The nutrient builders, the pioneer plants, the soil breaker-uppers, groundcovers,etc. already exist in the environment, who am I to fight
nature?, it has a lot more experience in this than I do.
Not to say I don't help a little by adding a bit of mulch here and there, spread seeds from the "weeds", cut out pine saplings,etc.

I have let a large part of my property go wild that was previously mowed / tilled for garden.
The "weeds" that have started growing, such as mimosa, rabbit tobacco, tall/short grasses,etc. seem happy as can be growing where previously things
I planted failed. After only a couple of years, there is a lot of organic material building up on top and the soil is looser. I find earthworms where previously there were none.

Next Spring I will try planting some crops into some of these areas.

i had great results with lucerne in sub mediterranean clay soil.

I would add Tree Lucerne, it can handle the heat and dry. It's better to keep them small and bushy, rather then big and straggley. I use them as stock food as well, can be useful for firewood. It fixes nitrogen, but of course you have to release the nitrogen through chop and drop, chipping, or stock food etc.