The Mediterranean garden year

Two seasons instead of four

A Mediterranean climate has a precise meaning. In the Köppen-Geiger classification it is a temperate climate with a dry summer, abbreviated Cs: the driest summer month receives less than 40 millimetres of rain and less than a third of what falls in the wettest winter month. If the warmest month averages 22 degrees or more, the type is Csa, with hot summers; if it stays below that but at least four months average 10 degrees or more, it is Csb, with warm summers. Besides the Mediterranean Basin, this climate occurs in four other regions of the world: California, central Chile, the Cape region of South Africa and the south and southwest of Australia.

For the garden, the decisive feature is that warmth and water arrive at different times. When the soil is warm enough for strong growth, it is dry; when it is moist, the days are short and cool. The wild plants of this climate have adapted: many grow in autumn, winter and spring and pause in summer. A garden that wants to manage with little irrigation adopts the same rhythm. The wet season is for planting, sowing and building soil, the dry season for protecting what has grown.

Autumn: the spring of the south

The first good rain after the summer, usually in September or October, opens the year. The soil, dry and hard for months, softens, the seeds of annual plants germinate and the hills turn green again. For the gardener this is what spring is further north.

The main reason is the roots. A tree or shrub planted in autumn has the whole wet season to grow into moist soil before its first summer. Reforestation research in Spain links the survival of young plants in Mediterranean plantations above all to how well they grow during the wet season, while summer drought is the main cause of losses. Gardeners in California, which shares the climate, give the same advice: plants set out in autumn root with the winter rains and need only a few supplementary waterings in their first summer or two. Planted in late spring, the same plant meets the heat with a root ball that has hardly reached the surrounding soil.

Autumn is also the time to sow. Green manure and cover crops go in with the first rain, grow through the mild winter and protect the ground when heavy rain falls on soil that has just come out of the summer. The fava bean, one of the oldest crops of the region, is sown in October or November and ripens before the drought. Cool-season vegetables such as cabbages, lettuce, onions, garlic and peas belong to this half of the year as well.

Winter: planting, pruning, catching water

In lower, frost-free locations the Mediterranean winter is a growing season, not a pause. Planting continues as long as the soil is moist and workable, and deciduous fruit trees can go in bare-rooted while they are dormant. Every tree that is in the ground before the end of winter gains time for its roots.

Winter is also the season for pruning. Support plants are cut when rainfall exceeds evaporation, and the cuttings stay on the ground as mulch: this is chop and drop. The cut lets light down to young trees, and the material decomposes on moist soil instead of drying out. Green manures keep growing and build up mass.

The third task is water. Rain that runs off in winter is missing in summer. Rainwater harvesting in its many forms aims to keep it: a roof water cistern stores it for the dry months, a swale along the contour lets it soak into the slope, and covered soil takes in more of every shower than bare soil. Winter storms also show where water runs, collects or carries soil away. Walking the land in heavy rain teaches more about it than any map.

Spring: mulch before the soil dries

Spring is the hinge of the year. Growth is at its height, but the soil begins to lose water faster than rain can refill it. The most important task now is to cover the ground while it is still moist. Mulch laid on dry soil keeps the dryness in; laid in March or April on soil still wet from winter, it keeps the moisture for weeks longer.

Green manures and covers are cut now, as a rule at the beginning of flowering and in any case before the soil dries out, because a stand that keeps growing draws on the same water the trees need. The cut material stays on the surface as mulch. Support plants and vigorous species are cut before their seed ripens, so that the mulch does not sow the next generation. When that moment comes is decided by the year: after a dry winter it comes earlier.

Spring is also the time for summer crops. Tomatoes, peppers, aubergines, beans, squash and melons are warm-season plants that do not tolerate frost. According to the Royal Horticultural Society, tomato seed needs about 18 degrees to germinate, and young plants go outside once temperatures stay reliably above 16 degrees. Around the Mediterranean that point comes earlier than in northern Europe, but these crops then grow into the dry season and depend on water. Mulch, some shade at midday and deep, infrequent watering make the difference.

Summer: protect, water deeply, observe

From about May to September the garden lives on what was prepared in the wet season. The guiding idea is protection, not production.

Shade stays. Support plants are not cut in summer, because standing shade protects soil and young trees better than any layer of mulch. Watering is sparing and deep: the Royal Horticultural Society advises watering less often but more thoroughly and letting the surface dry in between, for young trees and shrubs to a depth of 20 to 30 centimetres, where the roots grow, and preferably early in the morning. Buried clay pots, ollas, release water right at the roots with little loss. The aim over the years is a planting that lives on the winter rain stored in the soil.

Fire belongs to the Mediterranean summer. A wet season that grows plant mass, followed by months of heat and drought, leaves vegetation dry and flammable, and fire has shaped these landscapes for a very long time. In the garden this calls for general care: no dry cuttings or mulch heaped near buildings or along paths, green and moist zones around the house, and attention to local warnings.

Summer is also the season for observing and for seed. Many plants of the wet season ripen their seed in early summer, and the dry air makes drying easy. Seed saving from the plants that coped best adapts the varieties to the place, harvest by harvest. Which plants wilt first, where the soil stays moist longest, where the ground cracks: summer shows the weak points that the autumn planting can address. This is the practical sense of the principle observe and interact.

Limits: climate is local

No calendar replaces the place. The months named here are a frame for lower, largely frost-free Mediterranean locations, and even within one region conditions differ widely. Higher up, winters are colder and frost is regular, so tender plants wait for spring and the season shifts. Coasts are milder than inland valleys, south-facing slopes dry out earlier than north-facing ones, and on calm nights cold air flows downhill and gathers in hollows and valley floors. The microclimate of a single slope can matter more than the average of the nearest weather station.

The years differ too. The first autumn rain may come in September or only in November, and a dry winter brings the spring cut forward. The rule behind the calendar therefore matters more than its dates: plant and sow when the soil is moist, cover it before it dries, protect in summer. Whoever follows that rule and watches the actual year can respond to change instead of to a date.

How Terra Humana understands the garden year

For Terra Humana the Mediterranean garden year is above all a matter of water. In a climate where rain falls in one half of the year and growth is needed in the other, the gardener's work is to carry water from winter into summer: in the soil, in roots, in mulch and in stores. We plant with the rain, prune when rainfall exceeds evaporation and keep the shade in summer. The calendar is our starting point; what the land shows in a given year corrects it.