As Christmas approaches, the cold sets in at the Garden. In the Balearic Islands, as in the rest of the Mediterranean basin, winter is mild. Extreme low temperatures are uncommon in our latitude. Nevertheless, plants get ready to survive the cold and humid months ahead by adapting their metabolism accordingly.

Plants have no built in temperature control system as mammals and other animals do. Thus, the cold of the winter months limits a plant’s metabolic activity, and can even cause important damage when temperatures get below certain limits and freeze its tissues.

It might be expected that, in response to this situation, Mediterranean trees would loose their leaves, as do the deciduous trees in colder climes, in order to avoid ice crystals growing in their tissue, and the resulting death by freezing and cell rupture.

If this might seem a logical strategy, why are Mediterranean trees and bushes, such as the olive, the carob or the myrtle, perennial? What is the role of sclerophyllous leaves? Would it not be easier if they had adapted and shed their leaves in winter?

How does Mediterranean vegetation reacts to cold weather and occasional frosts?

A self-guided tour of the Soller Botanical Garden will help reveal the secret of this, and help to understand the rules by which our plants spent the winter, and the strategies which they adopt to survive the adverse season.

ITINERARY JANUARY/FEBRUARY/MARCH. BALEARIC FLORA

This corresponds to areas M1-M2-M3-M4-M5 as shown on the plan.

This self guided tour through the Soller Botanical Garden follows a path where one can find the scientific names on labels identifying each plant on the different areas as indicated on the plan provided by de Soller Botanical Garden.

Introduction

The low temperatures at night and the high humidity common throughout the Mediterranean basin slow down the metabolic activity required for the growth and development of plants.

Indeed, plants will develop no new leaves, and there is hardly any growth, if temperature is below 10ºC.

Shedding leaves is not a good energy saving strategy for Mediterranean shrubs or trees. Winter is so short that in a few months spring arrives and plants would have to generate a whole new foliage. This would require, in energy terms, great expenditure in nutrients. Instead their strategy consists of retaining their leaves and maintaining them at a slower metabolic rate. Most perennial Mediterranean plants also have sclerophyllous leaves, an advantage which allows plants to survive the adverse climatic conditions of both the winter and the summer.

In general, leaves go through the cold spell without producing new tender tissues that might, otherwise, get frost damage. Sclerophyllous leaves have, in addition, hard protective covering made of woody and cellulose material, as well as stomata, which are protected by a dense hairy growth that efficiently controls water loss. In this manner these leaves can survive temperatures below freezing without the tissue being compromised.

The deciduous plants, such as the lime tree or the ginkgos in the Botanical Garden, do loose their leaves in autumn, since they would not survive the cold winter temperatures. This a good strategy in really cold climates, however, the native flora of the Balearic islands include few deciduous plants since the winters are short and mild. If the cold spell is long, the production of new leaves every new season has an acceptable energy cost, since sclerophyllous leaves require more energy to build and maintain.

M1: Ruscus aculeatus

The Butcher’s Broom is a dense green shrub with rigid, spiny, false leaves or cladodes, on which, at Christmas time, globular red berries develop. In January, when fully ripe, the berries fall off, and are promptly replaced in February by the small new flowers. This peculiar plant bears its flowers in the middle of these false leaves, and with the flower is a second, very small, real leave. The false leaves are really modified flattened stalks.

M2: Medicago citrina

This shrub is endemic to the island of Cabrera, one of the smaller Balearic Islands, to small islets near Ibiza, and to the Columbretes, another set of small islands, which lie between the Balearic Islands and the mainland Spain. The plant is protected under de Endangered Species National Catalogue. Its buds appear during February, and soon become lemon yellow butterfly like flowers. The plant’s odd distribution may be due to over-grazing by herbivores on the larger islands.

The Soller Botanical Garden is currently engaged in a Conservation Plan for this rare plant in the Island of Cabrera.

M3: Querqus ilex

The Holm Oak is one of the most common evergreen trees found throughout the Mediterranean basin. Thanks to its leathery leaves can easily cope with the coldest winter. The leaves can survive frosts of –12ºC and the trunk of up to –20ºC. The tender new shoots only survive 0ºC.

M4: Helleborus lividus

Toward the end of January or the beginning of February this variety of Hellebore, or Christmas rose, begins its flowering season. Its bluish green leathery leaves sport purple undersides and contrasting pale white veins. The flowers, which do not have true petals, are pale green with tinges of purple, and have a high number of stamens with yellow anthers. This Hellebore is endemic of Mallorca and Cabrera. It can be found in shady, well protected, corners. There are other varieties of this Hellebore in the neighbouring islands of Corsica and Sardinia, as is Helleborus lividus subsp. Corsicus.

M4: Rhamnus alaternus

This bush is another common evergreen in the Mediterranean basin. It survives cold winters with frosts of up to –11ºC. It’s shiny green leaves are a delicacy for goats and sheep. Carefully inspection will show that leaf margins are completely transparent. Blackbirds and thrushes love their small black berries.

M4: Taxus baccata

The yew is a perennial tree with needle-like leaves, and very resistant to cold winters. In the Balearics it is found only in the high mountains of Mallorca where the air is cooler. Most of the yews found in Mallorca are young trees, planted only sixteen years ago. However, they can live for over a thousand years and grow fifteen to twenty metres high. There is a very old specimen in La Granja, in Esporlas, which is estimated to be more that two thousand years old.

The yew is a dioecious tree, that is, one that has single-sex plants. The male plant bears no fruit; the female plant bears small red berries, which are edible but not pleasant.

The remainder of the tree contains taxine, a poisonous alkaloid that can produce diarrhoea, vomiting, shortness of breath and even heart failure.

The wood, nevertheless, is much sought by cabinet-makers for is hardness and delicate patterns formed by its growth rings.

M5: Tilia plathyphylos

The linden or lime tree in de Soller Botanical Garden is well over one hundred years old. It was planted by the first owners of the building, then a farm-house, and survives splendidly among the wild Balearic plants in the collection. The tree looses its leaves in winter, since this species belongs to the deciduous forests of south west of Europe and occurs also on some of northern mountains chains of the Iberian Peninsula. Even without leaves, this is a majestic tree, and we like to think of it as Guardian if the Garden. In summer it produces flowers used locally to make an herbal tea as a remedy for those with a nervous disposition, or those who suffer insomnia. In winter it is enough to look up in silence at its immense size to peacefully enjoy its generous serenity.

M5: Hippocrepis balearica

This plant is locally known as "crag violet". It flowers in early winter and the common local name is due to the intense perfume given off by its little yellow flowers, especially at midday.

The aroma resembles the perfume of true violets and it attracts many pollinating insects. However, this beautiful plant is not related to true violets

A particularity of the genus Hippocrepis in the Balearic Islands is the variety within the species. The species of Hippocrepis found in each of the islands of Mallorca, Menorca and Ibiza are taxonomically different but had been regarded, until quite recently, as the same species. In this corner of Area 5, the more bushy Hippocrepis grossii from Ibiza can be compared with the Hippocrepis Balearica, growing on the upper part of the wall. This has a mat-like habit and will never become a bush.

M5: Micromeria inodora

From October onwards you can see this plant in bloom. During this period of cold weather it might be the only touch of colour on the rockery where the different varieties of Balearic thyme grow. The Micromeria inodora, or Thymus inodorus, belongs to the Thyme family and grows as a compact cushion producing small purple labiatae flowers. It is very common in Ibiza and Formentera, but in Mallorca it is only found in one locality near the slopes of the Xorrigo.

Mediterranean plants can easily survive winter increasing their defences until spring arrives, then new magnificent growth and new flowers will adorn the Soller Botanical Garden. Come and visit us again next spring when the Balearic flora will be at it’s best, full of colour and wonderful scen.