THE basis of good gardening is at the root of all plants, the soil or growing media. Much of the success of gardening is working with the soil to enrich it. Natural Mediterranean soil is often semi arid with low organic content due to the hot dry summers rapidly breaking down the organic content. To grow healthy plants in the Mediterranean climate you must have healthy soil.
Most plants we like to grow require healthier soil than nature provides. Indigenous plants have adapted to this environment and can thrive here but if you want a vegetable garden, fruit trees or exotic ornamental display, improving the soil expands the range of plants that you can grow.
Adding compost and manures to the soil will greatly improve the structure, texture, water holding capacity and the drainage of excess water in addition to the nutrients they provide. Protecting the soil from excess sun exposure is also equally important. The hot drying effect of the sun heats exposed soil to extreme temperatures literally sterilising the top layers of the soil killing shallow roots, worms and other soil surface ecology.
Many farmers use this sun sterilisation to keep fields and orchards weed free over summer by cultivating the soil at the start of summer. This works well for its purpose to keep areas weed free but has a long-term detrimental effect on the soil health and has the risk of erosion in high winds and heavy rain.
For gardeners it is better to develop strategies to protect the soil. Deciduous trees provide shade in summer over the garden but permit winter sun and the bonus of autumn leaves for mulch. I have a large Hackberry (Celtis australis) on the edge of my vegetable garden that gives midday shade over much of the garden in summer, drops its leaves into the garden in autumn for mulch and allows sufficient sun for the winter crops. The berries are edible and were often used during periods of food shortages as a supplementary addition to rationed food.
Another planting design that gives soil protection is a high planting density. Placing plants closer together gives shade over most of the soil areas of the garden just from the plants you want to grow.
There is a balance to be found with nutrient and water availability to support dense plantings but without good soil cover, evaporation of soil moisture is much higher and water holding, nutrient rich organic matter breaks down faster when exposed to the direct summer sun. Water loss occurs without the benefit of garden plants shading the soil and the plants add organic matter to the soil.