The Algarve has a Mediterranean climate – long, hot, dry summers with an average range of 20°-30°C, and cool, wet winters with an average minimum range of 4°-10°C. Its westerly location bordering the Atlantic means that the Algarve is generally wetter and windier (especially in the far west) than Mediterranean regions further east. Most plant growth ceases during the summer, with many plants surviving as dormant underground bulbs or corms until new growth is triggered by the first rains in the autumn, for example the native bulb Paperwhite Narcissus.
Winter rains usually begin in late September or early October, with showers continuing to March and April. There can be long dry spells during the winter months but the first rains produce a dramatic greening of the landscape. The first spring flowers appear in late January, and from mid March to late April the flowering period reaches its peak and the region is covered in a glorious blaze of colour.
As is typical of the Mediterranean climate, frosts are infrequent in the Algarve, allowing the extensive cultivation of tender fruits such as citrus and olives. Indeed, the distribution of the frost-intolerant olive (Olea europaea), which roughly tracks the winter 7°C isotherm across Portugal and the rest of the Iberian Peninsula, is a good proxy for the extent of the Mediterranean climate and the associated flora.
Such tender crops are usually grown along the warm southern coastal regions at lower altitude. At higher altitudes in the Serra (over 600m), for example the Monchique region, the climate is much cooler and occasional frosts are possible. More hardy fruits, such as cherries and plums, are grown along with vegetables, olives and citrus being restricted to the most sheltered valley terraces and lower slopes.
Throughout the Serra and lower hills of the Barrocal, cork oak, maritime pine and stone pine are extensively cultivated for bark, timber and seeds (nuts), respectively. Alongside them, ever-increasing quantities of Australian eucalyptus are grown, principally to supply wood pulp for the paper-making industry. The fire risks presented by extensive monocultures of eucalyptus are the subject of national debate.
The interrelated influences of geology and climate allow the definition of three broad geographical regions of the Algarve: Littoral, Barrocal and Serra, each with its own characteristic vegetation and flora.
The Littoral consists of the coastal land running along the southern-most strip of the region and up its western coast above the Cape St. Vincent peninsula. It has a mixed geology of sedimentary rocks, alluvia, and sand of relatively recent origin.
Inland, the Barrocal is an area of rolling hills, composed principally of limestone, that increase in height upon moving north, where they merge with the mountainous Serra.
The Serra is composed of older rocks, particularly shale and syenite, mainly carboniferous in origin. The high (300m) Serra is predominantly shale with occasional igneous intrusions, most notably the large mass of crystalline syenite at Monchique.
Through its influence on soil, particularly soil pH, the geology of these three regions has a significant effect on their respective floras. Thus, the Barrocal is dominated by plants that thrive on alkaline limestone soils, such as some Cistus species and Lavandula luiseri, with lime-intolerant and acid-loving plants being confined mainly to Littoral sandy areas and shale outcrops, such as gorse species (Ulex). By contrast, the acid Serra is dominated by plants that prefer lower pH soils, for instance Ericaceous species such as tree heath (Erica arborea), the strawberry tree (Arbutus unedo) and the iconic Cistus ladanifer.
In common with other Mediterranean climate zones, rainfall is predominantly during winter months. The amount varies between the Atlantic western coast and the drier eastern Algarve. The Algarve receives on average 453mm of rain annually but this can vary locally between 300mm and 600mm.
Irrigation water is available via an agricultural system in some areas, private boreholes and by municipal systems. The latter is very expensive and is not recommended for irrigation as it is drinking water. There are many homes with no access to a borehole or the municipal systems and they have large tanks which can be filled by rainwater harvesting or by the local firemen who deliver water at a cost. Careful plant choice according to your soils can deliver a sustainable and beautiful garden using native plants of the Algarve.
With grateful thanks to Chris Thorogood and Simon Hiscock, authors of the Field Guide to the Wild Flowers of the Algarve, Kew Publishing, 2014 – available from the Mediterranean Gardening Association.
|| Talk: What grows where? by Marilyn Medina Ribeiro
The first event of the new gardening year is an illustrated talk by Marilyn Medina Ribeiro on the important topic of ‘What grows where? Soils and plant communities in the Algarve’. It will be held on Saturday, September 23 at the Loulé municipal library (Sala Polivalente), from 10.30am to 12.30pm.
Learn more about creating a beautiful garden in harmony with your soil and the plants it will support. Discover how this understanding of our soils and plant communities will help you to improve and enrich your garden and save water. The talk will be held in English and there will be a discussion session also in Portuguese.
Marilyn Medina Ribeiro is plant adviser to MGAP. She has worked in nurseries, parks and private gardens and now lives in the Algarve, where she has managed hotel gardens and native plant gardens.
She now runs her own company, designing and building sustainable gardens and landscapes (www.waterwisegardens.com).
Entrance is free and all are welcome.
By Rosie Peddle
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Mediterranean Gardening Association – Portugal