Pearlworts, Ruptureworts and Allies
What are they?
This may at first seem a variable bunch of plants, but all are members of the campion family (Caryophyllaceae) and all are small, ground-hugging species. Many of them are easily overlooked as either their flowers or their leaves (or sometimes both!) are inconspicuous and don't immediately draw the eye; indeed, they may often be mistaken for mosses at times.
Where are they found?
Many species are annuals of open, disturbed ground, sandy tracksides or weeds of urban environments, including walls.
Identification
Habitat and then leaf shape will help to narrow your search, followed by details of the leaf and stems including presence or absence of hairs and whether they are simple or glandular. Note: the pearlworts included on here are the smaller species that tend to have petalless flower or flowers with only four petals. Larger pearlworts with five petals can look similar in their leaves to these species and can be checked by clicking here.
Procumbent Pearlwort Sagina procumbens
Native. Very common throughout the region, especially so in urban environments where it is abundant as a pavement weed. Flowers May to September. A mat-forming, almost moss-like, perennial plant whose stems trail and root at the nodes. Flowers appear at the ends of these trailing stems. Flowers petalless or with tiny white petals that are smaller than the the four green sepals. Leaf tips drawn out to a point which is less than 0.2mm long.
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Slender Pearlwort Sagina filicaulis
Native. Very common throughout the region, especially so in urban environments where it is abundant as a weed of walls and paving. Flowers May to August. Flowers petalless, the four green sepals with rather blunt tips, spreading conspicuously and becoming red-tinted in fruit. A tiny, slender, easily-overlooked annual that begins with a basal rosette of leaves which soon withers, leaving the flowers borne on slender, upright, non-rooting stems. There has been much confusion between this species and Annual Pearlwort with the two long regarded as subspecies of a single species (the present form then being Sagina apetala ssp. erecta). This has resulted in poor recording of the two taxa, but this appears to be the species most often found in urban environments, with Annual Pearlwort mostly confined to areas of open, sandy ground on heaths and similar places.
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Sea Pearlwort Sagina maritima
Native. Rare in East Anglia, being more a plant of rocky coastlines, but the small colonies that do exist around the coast are long-lasting and persistent. Typically on rocky substitutes such as concrete walkways close to the beach or on harder sand or shingle substrates. Flowers May to August. Flowers petalless, the four green sepals with rather blunt tips, more or less upright in fruit. Leaves thick and succulent with rounded tips and tiny points less than 0.1mm long.
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Annual Knawel Scleranthus annuus
Native. Once far more common and widespread but now much reduced due to soil enrichment and most likely to ber found in the sandy soils of Breckland or the Suffolk Sandlings. Flowers June to August. Flowers petalless, the four green sepals opening conspicuously and bearing a whitish edge, the white being only half as wide as the green part on the back. An annual species with no woody base and no non-flowering stems at flowering time.
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Perennial Knawel Scleranthus perennis
Native; endangered, with the subspecies prostratus being endemic to East Anglia. Once known from the Norfolk coast as well as Breckland, by the 1960s, this species had been lost to Norfolk and by the 1980s was confined to just three sites in Suffolk. Recent recovery programmes have increased the number of plants and it now occurs at a handful of Breckland locations. Flowers June to August. Flowers petalless, the four green sepals opening conspicuously and bearing a whitish edge, the white being nearly as wide as the green part on the back. A perennial species with obvious woody base and some non-flowering stems at flowering time.
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Four-leaved Allseed Polycarpon tetraphyllum
Native in extreme south-west England, this species is a very rare, non-persistent introduction as a weed of dry, sandy or gravelly places, or cracks in paving. Flowers June to August. Flowers greenish appearing petalless but actually with very short petals. Flowers similar to those of knawels but leaves distinctive, being broad and often in whorls of four. A low, creeping species that is small and easily overlooked but may increase in the region and should be looked for.
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Smooth Rupturewort Herniaria glabra
Very rare nationally and as a native now confined to just a few sites in the Norfolk and Suffolk Brecks and in Lincolnshire. A plant of bare, sandy or gravelly ground which, despite its rarity, can be very locally common if conditions are right. Flowers July to August. Flowers greenish appearing petalless but actually with very small, greenish petals. Flowers tiny and inconspicuous, but tight heads of developing fruits can catch the eye on yellowish stems trailing close to the ground.
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Hairy Rupturewort Herniaria hirsuta
Recorded in Norfolk as a casual introduction in 1917 and 1945 but not since. Flowers July to August. A prostrate annual of disturbed, sandy or gravelly ground; very similar to Smooth Rupturewort but the entire plant is covered in obvious hairs and it has a generally more greyish-green look to it.
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