Plants on the tidal Thames
The Thames is home to many different varieties of plants.
Phragmites australis is a common plant in wetlands across the UK, they form extensive reedbeds that provide an important home for many species, including bird species such as the reed warbler (Acrocephalus scirpaceus), the bearded tit (Panurus biarmicus), the marsh harrier (Circus aeruginosus) and the rare Bittern (Botaurus stellaris). Common Reed grows from rhizomes (underground stems) and flowers from August to October.
Typha latifoli is the archetypal “bulrush”, it has tall stems, sausage-like, brown flower heads and green, flat leaves. It occurs at the water's edge in wetlands, ponds, lakes, ditches and rivers. It flowers from June to August, but persists through the winter, often dying back to a brownish colour from its usual green.
Coastal saltmarsh is an important habitat for juvenile fish and as a feeding and roosting habitat for overwintering and migratory bird species. There are a number of important plant species that make up saltmarsh habitats.
Crithmum maritimum is found on southern and western coasts of Britain. It is a fleshy perennial plant found in crevices and ledges on sea-cliffs, coastal rocks and on stabilised shingle. It is also found in maritime grassland and saltmarsh and artificial habitats like harbour walls and sea defences.
Salicornia sp. is an annual plant and part of estuarine and coastal saltmarsh. It is found in western Europe and the Mediterranean. It is commonly seen in Thames saltmarsh. Sometimes called Marsh samphire, it grows on saltmarshes and beaches, sometimes forming big, green, fleshy carpets.
Atriplex portulacoides is a low shrub found in muddy or sandy saltmarshes, commonly fringing intertidal pools and creeks, and often forming extensive stands on ungrazed saltings.
Purple Sea Aster
Aster tripolium is a perennial herb that occurs at low elevations in ungrazed or lightly grazed saltmarshes, especially along creeksides, and on muddy sea-banks, tidal riverbanks and in brackish ditches. It also occurs very locally in inland saltmarshes and recently it has been recorded beside salt-treated roads.
Common Sea Lavender
Limonium vulgare can be found around our coasts on mudflats, creek banks and saltmarshes. Despite its name, it is not a lavender at all, so doesn’t smell like one. Common sea-lavender grows in muddy, salty pools or saltmarshes along the coast. Its flowers range in colour from blue through to lilac and pink and can often be seen densely carpeting the ground from July to October. Garden varieties of this plant are popular with flower arrangers as the flowers can be dried and keep their shape and colour.
Seagrasses are the only flowering plants able to live completely within seawater and pollinate underwater. Seagrass plants form beds, like underwater meadows, and are found in sheltered are, such as estuaries, bays and inlets, where the water level is shallow enough to allow photosynthesis. These beds provide nursery habitats for small fish, cuttlefish, shellfish and rays, shelter for juvenile fish and seahorses and their root systems provide habitat for small invertebrates. Seagrasses are also an important food source for many overwintering birds, such as geese.
Their root systems stabilise sediments, providing a form of natural defence in bad weather. Seagrass beds have an important role in mitigating climate change, they are responsible for approximately 15% of the ocean’s carbon sequestration. There are two seagrass species that are important in the Thames Estuary.
Zostera marina is a flowering perennial plant that grows in the subtidal zone, on substrates of gravel, sand or sandy mud in areas, where it is protected from exposure to the full force of wave and tide action. It lives on the very low shore to 10m deep and can form dense seagrass meadows. It gets its name from its long, eel-like leaves. The plants also have a rhizome, a type of underground root system that allows new plants to grow vegetatively.
Zostera (Zosterella) noltei is found on the mid and upper shore in wave and tide sheltered fine sediments. It is often found in small lagoons and pools, remaining permanently submerged, and on sediment shores where the muddiness of the sediment retains water and stops the roots from drying out. Beds of dwarf eelgrass provide important habitats for invertebrates, including the armoured bristleworm (Scoloplos armiger), the bristleworm Pygospio elegans and th blow lug (Arenicola marina).