Monday, 29 June 2020

Wildflower of the Month: June: Bee orchid

Bee orchid at Monk's Wood, Cambs.
Image: Kevin Walker
In recent months Dr Kevin Walker, BSBI Head of Science, has been focusing on a different wild flower each month. In March it was purple saxifrage, in April it was snake's-head fritillary, May's Wildflower of the Month was meadow saxifrage, and now Kevin focuses on a plant we usually think of as blooming in June on calcareous grasslands in the south. Except that's no longer the whole story... 

Read on to find out what Kevin has discovered about one of our most popular and iconic orchids! 

"Orchids are our most glamorous wildflowers. They are an entry point for generations of botanists and even pique the attention of birders when the flow of spring migrants dwindles to a slow trickle in late May. Their exquisite beauty, complex sex lives and often extreme rarity gives them an allure that is hard to resist and can lead to life-long obsessions. As BSBI member Leif Bersweden captures so beautifully in The Orchid Hunter, it was the discovery of a Bee Orchid as a boy that got him hooked. Leif is in good company. Charles Darwin devoted much of his later life to the “various contrivances by which British and foreign orchids are fertilised by insects” – a book with superb descriptions and line drawings of the fascinating sex lives of many British species.

What's the collective noun for bee orchids:
a swarm?
Image: Rebecca Wheeler
"June is the premier month for orchid hunting. Many of our c50 species flower in quick succession and, if you are lucky enough to know where to look, there are well trodden paths to all but the very rarest species. Wisely, the hallowed locations of the likes of Lady’s-slipper, Red Helleborine and the ethereal Ghost Orchid remain under wraps. The most talked about orchid of them all is the Bee Orchid Ophrys apifera. This colourful mimic, with its bee-like flowers, is one of our most widespread orchids and increasingly the one you are most likely to find closest to home.

"Historically its beautiful blooms were to be searched for in chalk downland, coastal dunes and damp meadows and pastures. But today it is as likely to be encountered on urban road verges and waste ground, or as a colonist of quarries and gravel pits in the early years of succession to more stable grassland and scrub. If you live in England and have never seen one then ask around. Most botanists will know where to find one.

Bee orchids in a sward
Image: Richard Bate
"The fortunes of the Bee Orchid are worthy of a book in itself. It appears to be on the move both ecologically and geographically and these changes are providing tantalising insights into how our environment is changing; if these early indications are correct, it may well be the ‘canary in the cage’ when it comes to climate change and plant conservation.

Close to home…
"One of the wildlife highlights of these long lockdown months has been the abundance of wildflowers in urban areas where councils have relaxed their mowing regimes. This, combined with Plantlife’s #NoMowMay campaign, has led to a surge in records of Bee Orchid. Since it was first reported in flower on the 15th of May by Dr Richard Bate, Twitter has been alive with records, many from garden lawns: participants in the BSBI’s Garden Wildflower Hunt have been sending us records of bee orchid sightings in their gardens and telling us how delighted they were to welcome these visitors!

"My nearest colony is about fifty metres from my front door. I’ve been keeping a close eye on this little colony and these observations have been very revealing. The first thing to note is that it is flourishing on a very ordinary roadside verge which can only be described as a billiard table. Most of the plants rarely, if ever, get a chance to flower; those that do have to endure football games and mowers and this year a severe frost in late April followed by a month-long drought in May. Many blackened off and died back. A few have flowered probably a week earlier than normal. Flowers first appeared on “my” bee orchids on the 2nd of June. In normal years (whatever that now means!), they are usually at their peak between 9th to 24th June. Anecdotally botanists tell me that it was never worth looking for their flowers before mid-June.

A meadow full of bee orchids and other
native wildflowers
Image: Rebecca Wheeler
"What’s also revealing about “my” colony is its location. It’s not particularly special – just some grass strips in a modern housing estate built on a former MoD site in the 1990s. The grassland, which is not totally devoid of interest (Knotted Clover Trifolium striatum grows with the bee orchids), could have survived the construction work or was possibly seeded afresh, creating ideal conditions for Bee Orchid – which likes bare ground - to colonise.

"So it is not surprising that we are getting lots of reports of Bee Orchids in garden lawns. This reminds me of another orchid that made a spectacular appearance in gardens after the scorching summer of 1957. Severe drought meant that many lawns were left uncut and this led to flurry of reports of Autumn Ladies-tresses Spiranthes spiralis from gardens, so much so that it was reported in The Times. This mass seeding event lead to a dramatic increase in populations in subsequent decades, so perhaps an unintended consequence of this lockdown will be a similar increase in Bee Orchid colonies in years to come?

Spreading north…
Graph showing northward spread of
bee orchid over time
Graph by Kevin Walker
"Scientists have shown, unequivocally, that some butterflies, dragonflies and birds are expanding their ranges northwards as climate change opens up new areas of habitat to them. Evidence for plants is much harder to come by: maybe that’s not that surprising. Wildflowers are by nature sedentary; they don’t move much and if they do, their dispersal is measured in metres rather than kilometres. The main exceptions are orchids. Each flower produces thousands of dust-like seeds and these can be dispersed over large distances by air currents. It has even been suggested that the North American orchid known as Irish Lady’s-tresses Spiranthes romanzoffiana, a rare plant of the western seaboard of Britain and Ireland, might have been blown across the Atlantic during gales. The attractive Mediterranean tongue orchid Serapias lingua appeared in Essex a few years ago and again wind dispersal has been mooted as the means by which it arrived on our shores. In both cases there are other theories but the most parsimonious would seem to be wind. 

Bee orchid
Image: Richard Bate
"Of all the British orchids, Bee Orchid has shown the most spectacular increase in recent decades. Back in the 1960s, it was largely confined to grassland in southern and south-eastern England with odd records stretching as far north as County Durham. Since then it has been gradually extending its range northwards (see the graph above) especially in northeast England where it has spread along the coast. It was first recorded in Scotland in 2003 and now occurs as far north as Glasgow and Edinburgh, and I’m sure it will spread further, probably in sandy grassland along eastern and western coastlines, in the not too distant future.

"As intimated above it also appears to be broadening its ecology. In the first edition of Clapham, Tutin and Warburg’s Flora of the British Isles, published in 1952, its habitats were described as “pastures, field-borders, banks and copses on chalk or limestone, especially on recently disturbed soils; also on base-rich clays and calcareous dunes.” Today you are as likely to see it off calcareous soils as on them, on roadside verges, spoil heaps, urban waste ground, disturbed soils in old quarries and gravel pits and abandoned farmland.

Seeds of its success…
Bee orchid close-up
Image: Richard Bate
"So what is the secret of the Bee Orchid’s success when so many other wildflowers have declined? Despite its bee-like appearance, self-fertilisation appears to be the norm rather than deception to entice cross-pollination by bees (as in other Ophrys species). Unlike some other orchids, individuals can continue to flower for a number of years. As a consequence, populations are likely to grow very quickly. This coupled with its ability to spread its seed far and wide means that it can quickly colonise new habitats as they come within reach.

"Like most plants, orchids face a trade-off when it comes to seed size. Dust-like seeds are great for getting around but do not have enough food to support the growing embryo once they land. Many orchids strike a deal with soil mycorrhizae gaining nutrients from the fungus as they grow. But this is the Achilles heel of many orchids species and the reason they are so rare; highly specialised relationships severely restrict where they can grow. We can only assume that the Bee Orchid has chosen a range of very widespread and common fungi with which to share its food.

Bee orchid rosette with 20p coin
standing in for a scale bar
Image: Kevin Walker
"But possibly at the root of its success has been its ability to adapt to rising temperatures in recent decades. Bee Orchids are wintergreen; in fact, winter is the easiest time to spot their distinctive rosettes. Many participants in BSBI’s New Year Plant Hunt spot the rosettes while they are out looking for wild plants blooming in midwinter. Mike Waller’s Beginner’s Vegetative Guide to Orchids of the British Isles is very helpful for anyone who isn’t sure what to look for. As our winters have become less severe, Bee Orchids have clearly benefited especially in urban and coastal areas, where severe frosts are less common.

"We humans have accentuated these trends by creating the disturbed, early successional conditions that they seem to love. Since the 1950s we have transformed our lowland landscapes through a massive expansion in road and rail networks, industrial land, waste ground, restored colliery and landfill, and abandoned quarries and gravel pits. Bee Orchids have benefited from these transformations.

"So the Bee Orchid is probably the nearest wildflower we have to a ‘canary in the cage’; its fortunes tell us much about how our climate and landscapes are changing. But more than that, this adaptable little orchid continues to enthrall and excite us; as the celebrated and much-loved illustrator Cicely Mary Barker observed in her ‘Song of the bee orchis fairy’, a day when you discover a Bee Orchid is always 'your luckiest day'!” 

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