Posted by Lou Astbury on


And flowers for the cautious.

 The Spring air is full of pollen. It’s not something people think about much, unless you suffer from hay fever or park your car under a tree and notice the dust. 

But pollen is totally extraordinary. And trees send out enormous amounts this time of year.

Pollen is the ingenious solution to the challenge of reproduction between two beings who can’t move to find each other.

But what’s probably most extraordinary about it is the scale. While huge amounts of pollen are released, the individual grains of pollen are tiny. Microscopic. Yet, each grain contains all the male genetic material needed for new life - the life of the biggest organisms on the planet. A pollen grain has a hard outer shell to protect the precious genetic material inside during the journey from one tree to another. And under a microscope they reveal incredible forms and shapes. Google ‘Scanning Electron Microscope pollen’ and you’ll be blown away by the imagery.

When the pollen reaches the female flower the biological marvel of fertilisation happens, the result is the growth of fruits and seeds (nuts) and the potential new life of the next generation. Plus a bounty to fuel up the food chain.

For tree species in higher latitude and elevation - most common in our temperate deciduous and boreal forests - wind is the most common strategy of dispersal. By contrast, it is an extremely uncommon method in tropical rain forests. There, animal-aided pollination – especially by insects – is the norm.

Wind pollination is most effective in open habitats and in early successional ecosystems (think birch and scot’s pine), where wind is likely to be an advantage. And among forest trees that reach canopy height and whose flowers or cones are exposed to winds. Wind pollenated trees all share a common male flower form: they tend to occur in elongate, drooping catkins well-positioned for wind dissemination.

But this method is still pretty risky, so trees hedge their bets by producing enormous amounts of pollen. Just one cluster of birch catkins can release ten million grains. Billions of pollen grains from a single tree. 

By contrast, the more cautious and seductive approach comes from trees that rely on pollination by animals (mostly insects, but also birds, bats and other mammals) - they tend to produce far less pollen in a flowering period, because pollination is more direct and efficient. Apple trees, cherries, horse chestnut, hawthorn, willow etc. They tend to have fragrant, large, or showy amounts of flowers. They offer the promise of food in the form of carbohydrate-rich nectar and protein-rich pollen. 

There has been a revival of interest in scientific studies into pollen recently. The other evening I got lost in academic papers looking at the potential effect of pollen on weather patterns - recognising that forest pollen is a heavy contributor to atmospheric bioaerosols during spring months. This is important because bioaerosols make up 25% of the atmospheric aerosols shaping cloud formation, precipitation and ultimately climate. And how pollen contributes to lake health - feeding water with nutrients and minerals for aquatic life to thrive.

Pollen is also nutritious for us. Pine pollen is an ancient superfood, there are written accounts of humans ingesting pine pollen for health benefits from 200AD. 

Nothing within natural systems is without reason and deep purpose. All interrelated. The Spring release of pollen is probably far more profound than we realise. 

Thank you for following the pollen.

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