Rock samphire, C. maritum is a monotypic species, with fleshy leaves, from woody stems and greenish-yellow flowers. It's in the family Apiaceae and is edible. As is golden samphire, Limbarda crithmoides (in the Asteraceae family), however the more popular samphire is Salicornia spp, in Amaranthaceae. All are found around the coastline of the UK.
As with all umbellifers, the heads of numerous tiny flowers provide a huge resource of nectar and pollen for a wide range of insects from tiny pollen-beetles to large hoverflies. The leaves and stems of Crithmum are tough with a greyish waxy coating making this supremely well-adapted to living in very dry conditions - an excellent addition to any gravel garden.