Going native

Our land is now free of christmas trees. Time to plant some natives. At the side of the small hay meadow I planted an Elm (here in the foreground) and a Silver Birch (Betula pendula). 

Elms are a much rarer sight than they used to be. In 1910 they began to die. By the end of the century France had lost 97% of its trees. My elm tree is a symbol of 'girl power' in science. I have planted it on the centenary of the discovery of the cause of the disease that was killing the elms - a fungus called Ophiostoma - by an all female team in the Netherlands (thus 'Dutch Elm Disease`): Johanna Westerdijk (the first woman to become a professor in the Netherlands - in 1917, two years before she was allowed to vote), and her two PhD students Bea Schwarz and Christine Buisman. (I was once interviewed for a job at Glasgow University - the successful candidate was a woman working on the molecular taxonomy of elms, and I now wonder if she knew about the female Dutch pioneers).

The Dutch made an Ophiostoma resistance programme from 1928 to 1992, resulting in three highly efficacious cultivars - one of which is 'Nanguen', raised in Wageningen (the Agricultural University where I worked for two years). It is the cultivar most closely resembling native European elms. It was screened in France, where it is now sold under the name Lutèce ('Nanguen' is a contraction of Nancy & Wageningen). I have planted a 'Nanguen'. This cultivar is now being planted for butterfly conservation, namely of the White-lettered Hairstreak (Satyrium w-album) which only lays its eggs on elms. I'm not sure a single tree will attract them, but who knows.

Nearby I have planted a Rowan (Sorbus aucuparia). It should delight with its white flowers in summer, providing food for insects, and in Autumn its red berries will provide food for birds (aucuparia comes from the latin words avis for bird and capere for catching). 

Marianne wanted a Walnut tree. We do have a small one trapped in a hedge in the shade behind the house, but it will never realise its potential - given enough space and light a walnut tree can reach a height of over 30 metres with a trunk over 2 metres in diameter. I have planted a Juglans regia, the so-called Persian Walnut, a native from Europe to China, in the most open space of the front garden, in front of the large hay meadow. We are not alone - in France walnuts are the second orchard crop by area, grown on around 20,000 hectares, and we live in the most important region. I doubt we will be a major supplier of nuts, but we may sit on a bench under the shade of a magnificent crown.

I've also planted some fig trees (Ficus carica), each a different variety - the flavour and smell of the Mediterranean and Middle East. Figs like it sunny and dry. I've planted one by a south facing wall, next to the large hay meadow.

Another two figs are at the side of the potager meadow. I don't know if its the best site, but I live in hope.

Delicious fruit is not a reason to grow figs - because the part you eat is not the fruit, it's a fleshy pod inside which little male and female flowers bloom and form little true fruits when pollinated. The wonder of figs is their need to be pollinated by a fig wasp, Blastophaga psenes.

At the base of the flower pod is a hole. A female fig wasp will fly into the hole, carrying pollen from another fig, and lay her eggs in some of the flowers - whilst at the same time pollinating other female flowers. The wingless males will then hatch first and mate with females before they have hatched. The males will then dig holes in the pod for the females to escape, and then die. Male fig wasps never see the world outside a fig pod. The females fly out, having collected pollen on their way - and the cycle continues. You couldn't make it up!

Postscript:

Back in Basel for Chistmas, I take walks in my local wood - an ancient wetland, now canalized. There, lining a stream, are a number of large elms. One of them has recently been labelled. It says the tree is a White Elm (Ulmus laevis) that is between 200 and 250 years old. This is a species of north-eastern Europe, that reaches its western limit in Switzerland. It is one one of the few elms that can tolerate watterlogged conditions (as this area would have been when these trees were saplings) and it even relies on flooding to transport its seeds. 

A characteristic of the species is that the leaf veins beyond the lobe are undivided.

I can hear you shouting at your computer screen "but Dutch Elm Disease killed all the big elm trees!". Well, many White Elms did not suffer from the disease - not because they are resistant to Ophiostoma, but because their bark contains a chemical called Alnulin which is distasteful to the Elm Bark Beetles (Scolytus species) which carry the disease. The beetles would rather feast on Field Elms and Wych Elms.

The answer to the question 'when is the best time to plant a tree' is 'twenty years ago'. But really, it's never too late to plant a tree - as long as it's a native.