Understanding Italian soil – The key to successful gardening in Italy

Italian soil

Italy is, essentially a very long piece of rock and the types of soil that can be found up and down the length and breadth of this rocky peninsula vary immensely. Soils range from friable acidic sand in the Dolomite mountains in the North, almost unworkable clay loams around Bologna and in Tuscany to poor, dry calcareous crusts along Italy’s coastline.

Therefore, if we to attempt to generalise ‘typical Italian soil’ it would be rather like trying to settle upon the ‘typical’ pasta dish in Italy, as the soil in Italy is as localised and diverse as Italian cuisine is. Clearly, Italy’s plants have evolved for thousands of years to cope with the soil conditions in Italy and one now finds a range of flora from wild azaleas that appreciate an acid soil in the Dolomites to chalk-loving Mediterranean plants like Rosemary, by the sea.

Careful thought must be given to the type of soil on which your green space finds itself before making an Italian-style garden in Italy. A basic test with a pH indicator will establish whether your soil is of an ‘acid’ (low pH) or an ‘alkaline’ (high pH) soil type and an even more simple soil examination can be carried out without any equipment. Simply take a small lump of moist soil and begin rolling it in the palm of your hand, if you manage to form a ‘worm’ shape out of the lump and if it feels silky and not gritty to the touch is likely to be composed of clay .

In Italy most of the clay soils present are generally more likely to be of an alkaline (chalky) nature and can often be even thicker than a standard clay soil. These heavy clay/alkaline soils tend to waterlog easily and, subsequently drain badly, remaining wet and cold during the winter. These cold/damp winter conditions will rot the roots of most Mediterranean plants. Instead, during the summer this kind of clay soil generally becomes set like cement under the hot Italian sun, creating problems for root growth.

Tuscan landscape photo ©iStockphoto.com/Rolphus

Tuscan landscape photo ©iStockphoto.com/Rolphus

However if the ‘worm’ shape that you have moulded in your hand instantly breaks up while rolling it then it is likely to be of a sandy nature, which is always free draining and generally tending towards an acidic pH. This acidic, sandy soil is clearly ideal for acid-loving plants (‘calcicole’), such as camellias, rhododendrons and hydrangeas, etc. The free-draining qualities of sandy soils generally benefit most Mediterranean plants and an alkaline sandy soil could be considered one of the ideal soil types for most Mediterranean plants. However, by far the best soil type for growing the ‘classic’ Italian plants like the olive, lavender and most other Mediterranean plants is a free-draining, poor, rocky alkaline soil, the type which one would generally find near the coast. Mediterranean plants are native to this kind of soil and thus, they have adapted perfectly to growing in the conditions that it provides.

Let it be said that planting a (calcifuge) in an alkaline (lime) soil will almost certainly prove fatal, both for the plant and the wallet, and the same goes for when planting a (Calcicole (lime-loving plant) planted in an acid soil. A plant that is growing in the wrong soil will soon display signs of suffering through stunted growth, yellowing leaves and general poor performance. The key to gardening well in Italy is understanding the important effects that soil type and pH have upon the plants that you plan to plant. Therefore, it is essential, to establish this before embarking on planning the plants for any Italian garden project.

Plants for an alkaline soil (calcicoles) include:

  • Olive
  • Lavendar
  • Tomatoes
  • Artichokes
  • Bearded Iris
  • Rosemary
  • Sage
  • Thyme
  • Caryopteris
  • Gardenia
  • Aloe
  • Vine
  • Agave
  • Feijoa
  • Pittosporum

Plants for an acid soil (calcifuges) include:

  • Rhodendron and azalea
  • Most conifers
  • Hydrangea
  • Camelia
  • Acer
  • Heathers
  • Birch trees
  • Ferns

As you can probably from these lists, the plants that prefer alkaline soils are easily recognised as “Italian plants” or “Mediterranean plants”. Therefore it should go without saying that the choice of Italian soil is almost as important as the choice of Italian house, if one plans to create an Italian style garden space!

It is possible to improve a clay soil over time by adding organic matter and sharp sand to improve drainage and pine leaves can be added to lower the pH (or raise acidity). However for acidic, sandy soils one can scatter basic lime (Calcium carbonate) to raise the pH (or lower the acidity) this is known as ‘liming’. Whatever kind of soil you find yourself with, it’s imperative to know what that soil is and what kind of plants can be established on it before designing an Italian garden.