Alpine flowers are unique, hardy species that appear brilliantly yet fleetingly during summer at high altitude. The challenges these tiny plants have to overcome are enormous: extreme temperatures, fierce winds, shortage or excess of moisture, thin soil, threat from livestock and humans and competition for reproduction. They need to do their utmost both to survive and to reproduce, and they have developed remarkably ingenious mechanisms to adapt to the range of stressful factors in their habitats. To say that alpine flowers have perfected survival techniques is an understatement!
Survival Techniques
The formidable mountainous barrier of the Alps begins close to sea level and soars to over 4000m, experiencing dramatic extremes of temperature. Cold is a crucial issue – for every 100m rise in altitude the thermometer drops by about 0.6°C. Moreover, there can be a 20–30°C difference in air temperature between day and night – and that’s only at 2000m.
Challenges notwithstanding, a good 52 alpine flowers are known to survive up to 3500m above sea level, while an amazing 12 species make it to the 4000m mark. The record holder for altitude is the Glacier Crowfoot; an exemplar was reported on the 4274m Finsteraarhorn in the Swiss Bernese Alps. The leaf cells of the highest growing flowering plant in Europe contain a high concentration of sugar which acts as an anti-freeze, lowering the freezing point of its tissues and thus enabling it to live amid snow and ice in sub-zero temperatures. Incredibly, the plant is able to photosynthesise even at -6°C.
Strange as it may seem at first, snow cover is essential to many alpine plants. It acts as a source of moisture and nutrients, but also provides protection from winds and extreme temperatures during the harsh winter months; however, it may mean they are under cover for eight months of the year. The air temperature drops dramatically, especially at night time, and when, for instance, the thermometer plunges to -33°C outside, snug under the snow it may be a comfortable -0.6°C, allowing the plant to function, albeit in a sort of hibernation. The Alpenrose seeks out north-facing slopes where snow accumulates to be sure of long-lasting blanket cover. Such plants can usually survive at temperatures as low as -25°C, which would seem amazing if it were not for the -70°C limit of plants that deliberately grow on windy crests! By contrast, dwellers in nooks and crannies on vertical rock faces, such as Devil’s Claw and Moretti’s Bellflower, cannot count on snow protection, but they are out of the range of chilling winds.
In spring as the white stuff starts to melt, light begins to filter downwards and triggers photosynthesis as the plant wakes up. Here the Alpine Snowbell comes into its own. One of the first blooms to appear in springtime, it can often be seen pushing its way up through the snow; in fact, the heat it releases as it breaks down carbohydrates can actually melt the snow.
The Alpine Snowbell pushes its way up through snow
Unstable terrain, such as the mobile scree slopes or talus found across the Alps, proves another challenge. Fragments of rock falling from higher rock faces and cliffs are constantly adding to the slopes, accumulating on the surface and provoking a downhill slide. A well-anchored root system is essential for any plant to be able to call such terrain its home. Alpine Toadflax and Rhaetian Poppies are experts in this regard.
Survival techniques involving moisture are two-fold: retention and removal. Cactus-like succulents are experts at reducing moisture loss, with their thickly cuticled leaves, and they also have the ability to store water in their stems for times of need. The Cobweb Houseleek is true to its name and has a thick layer of soft netting on its rosettes, which additionally slows moisture loss from the plant’s surface.
Small leaf size can effectively minimise evaporation, and a good example is Moss Campion. The technique used by the Edelweiss is to cover itself with white woolly hairs, which not only reduce moisture loss but also protect the plant from the strong solar radiation encountered at high altitudes. These hairs can also create a micro-climate around the plant where the temperature is slightly higher than that of the surrounding air.
In contrast, Lady’s Mantle practises guttation, a process occurring under conditions of high humidity, particularly at night, whereby the plant exudes surplus water to the rim of its leaves. The drops of water are often mistaken for dew; these drops were treasured by ancient alchemists who claimed they could transform metals into gold – hence the genus name Alchemilla.
In a similar way, Saxifrage plants on limestone rock may find themselves overwhelmed by calcium salts. While the plant uses some for its physiological requirements, it banishes the excess to the edges of its leaves, and the resulting encrustations have the bonus effect of reinforcing the leaf itself.
Calcium salt encrustations on Saxifrage leaves
Keeping a low profile as a protection from the elements is a successfully tried and tested technique used by the likes of Alpine Rock Jasmine, which barely attains a height of 3cm. However, below the ground it develops a root system that serves as an anchor, penetrating all available cracks in the rock. Saxifrages are also renowned specialists in this. With a genus name that means ‘stone-breaker’, the roots do just that, fracturing the rock into particles and delving down, providing stability for the plant while also on a quest for moisture. A number of prostrate woody shrubs such as Retuse-leaved Willow have networks of slender roots and branches that creep over rock surfaces, acting as anchors.
Moss Campion produces a cushion where small creatures can live
Moss Campion grows painstakingly slowly over its 20–30-year lifespan, producing a woolly cushion rich in humus where small creatures can live. Another plant that takes its time is Alpenrose, which needs 8–10 years for its seeds to mature into flowering plants. Then there’s Net-leaved Willow: it has been calculated that a trunk as slender as 7mm could be 40 years old. Nature outclasses the bonsai masters!
Many alpine plants practise solar tracking, which is also known by the rather forbidding term of heliotropism. In addition to placing their leaves perpendicular to the sun’s rays to maximise exposure and encourage photosynthesis, they make constant alterations to the angle of their flower heads so as to receive the full blast of the sun’s warming rays all day long. Buttercups with their yellow saucers are experts in this field; they are able to store heat and the temperature inside the petals can be 8°C hotter than the surrounding air: a great lure for insects that need warm conditions as well as a boost for the plant itself as seed development accelerates. Should the heat become overwhelming, the plant can rotate its ‘satellite dish’ parallel to the incoming rays to reduce exposure; this also minimises moisture loss, essential in dry habitats.
The Carline Thistle, on the other hand, has the advantage of hygrometric (moisture measuring) equipment in the scales that envelop its flowers. This is triggered in adverse weather and the flower closes up in self-defence; it will then open when conditions improve. This behaviour has earned the plant the reputation of being a reliable weather forecaster.
Reproduction
In their very short annual growth period, concentrated into 100 days at most, survival is not the sole life purpose of alpine flowers; reproduction is also crucial. Generally speaking, a plant’s growth period and opportunity to reproduce is shortened by a week for every 100m of altitude. A mind-boggling array of techniques has been invented by flowering plants in order to encourage pollination and spread their seeds, and competition can be fierce.
A Painted Lady butterfly with Round-leaved Pennycress
Attracting insects
Colour is a key factor in attracting insects which, while feeding, inadvertently gather pollen and spread it, thus improving the plant’s chances of reproduction. Many alpine flowers only bloom for the two midsummer months of July and August, and the plants make the most of it with a brilliant display of livery.