War!

Primula Wars

David Beeson

Primroses are as much part of spring as bumblebees and the first butterflies. A wander through Harewood, or any similar habitat, will delight your senses. The primrose yellow (What other colour could I call it?) of their blossoms enliven the green of the fast-growing ground vegetation. Nearby you’ll spot blue and white violets, wind flowers (wood anemonies) and possibly wood sorrel with its delicate white flowers. The dog’s mercury flowers, they’ve separate male and female plants, are waning yet their leaves stay put all year despite the shade of the hazel and oak trees.

Look as closely as you might, but it is unlikely you’ll spy the primrose’s close relative – the cowslip, on the woodland edge.  Both primulas, but evolution has sent them down different paths.

My own garden abuts Harewood forest. The forest throwing a delicate shade over the end four or five metres of our garden. Of course, the degree of shade varies with the elevation of the sun and so the light levels change. Nearest the boundary the light levels are lowest and they rise as one moves away, until near 100% light falls.  This is how the light changes on any woodland or glade edge.

Within Harewood, beyond our boundary, there are 100% primroses. Just into the garden it is the same. With 100% light we have 100% cowslips and where the light levels change with the time of the year we have a mixture. The mixed boundary is thin – only a metre .

Presumably the primroses cannot cope with the temperature associated with 100% light levels and cowslips gain too little light energy under a woodland edge’s canopy.

There could be other reasons for this ecological separation. The soil within the woodland will have potentially more humus and the forest’s herbivores could more readily eat the cowslips. With differing flower designs the two species will have different pollinators and the dispersal mechanisms may cause the other habitat to be unsuitable. It sounds like a PhD project here!

Elsewhere in the garden we have long had some colourful polyanthus. These plants are a ragbag of mixes of many different primula (Primulaceae) species (of which there are perhaps 100+). The insects have been spreading the pollen of these colourful polyanthus plants around and some has been donated to our wild primula population. This has resulted in pink primroses, deep red cowslips and cowslip x primrose hybrids. This latter looks like an oxlip, but technically is not. That is a separate species found naturally only in East Anglia.

Just as there is war between the primroses and cowslips at Forest Edge, so the same occurs in East Anglia between oxlips and primroses.

It seems that primroses produce seeds containing a small food store, which attracts ants. The woodland edge ants carry off the seeds and so aid their local dispersal. The oxlips seeds have no such help and these plants occur deep inside the wood where those ants do not reach.

In the early days in developing our wildlife-friendly garden I bought in wild bluebell seeds. They were, in fact, Spanish bluebell seeds but we only found that out years later when they flowered. Native bluebells naturally occurred in the garden and the two have crossed. We now have 100% pure native types, 100% Spanish and every combination in between. This is not good as there are genuinely wild English bluebells nearby. I have most probably contaminated them. It is impossible to correct this damage.

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