For many people who favour traditional seaside holidays, there’s something slightly disappointing about a shingle beach. No sandcastles, no burying your toes in the soft, sun-warmed grains. Just hard pebbles underfoot, clattering as the waves wash in and out.
But shingle does have some advantages beyond a grit-free picnic. At Hayling Island, long stretches of sand are exposed at low tide; above the high-tide mark, however, it is now maintained through the placement of shingle via beach recycling to absorb wave energy and provide natural protection against coastal erosion. More than this, the well-drained, nutrient-poor pebble substrate provides a perfect habitat for plants adapted to thrive in harsh conditions.
Between the candy-striped beach huts, a few late-flowering yellow horned poppies (Glaucium flavum) bloom among pink clouds of thrift (Armeria maritima) and vibrant blue tufts of viper’s bugloss (Echium vulgare). But it’s the broad clumps of sea kale (Crambe maritima) that have drawn the attention of a trio of small white butterflies (Pieris rapae). A female is nectaring on the clusters of tiny, honey-scented white flowers, while two males compete for her attention, fluttering, hovering, then spiralling upwards as they attempt to outmanoeuvre each other.
It’s easy to distinguish between the sexes, as the males have a single black spot on each forewing, while the female has two merging dab marks below the centre of each forewing in addition to the single spot. The wing tips and leading edges look as though they’ve been dusted with soot, suggesting that these individuals have recently emerged. Adults of the summer brood generally have darker markings than those of the spring brood. As my shadow falls across the female, she claps her wings shut, exposing the clotted-cream-coloured undersides.
Once mating occurs, the female will lay her conical eggs singly on the underside of the lobed, wavy-edged, glaucous sea kale leaves. This long-lived perennial is a primary larval food plant for the velvety green caterpillars, whose powerful jaws make short work of the thick, waxy cuticle. The blanched stems, florets, and seed pods are considered a culinary delicacy, although, as a border terrier scampers over and cocks its leg against the plant, I decide it’s best left for the butterflies.