In calcareous or other mineral-flushed sites, you may find Few-flowered Spike-rush ⇒Eleocharis quinqueflora looking like a small deergrass.
The deergrasses have a short blade to the upper leaf-sheath, completely lacking in spike-rushes.
Deergrasses usually have far more stems, and far more densely tufted tussocks.
leaf-blade on upper leaf-sheath of deergrass
newly-emerged Eleocharis quinqueflora; note lack of leaf-blades
Dioecious Sedge Carex dioica (below, right) can also look similar, but the stem-leaves have obvious long leaf-blades.
(five stems on left) Eleocharis quinqueflora;
(four stems on right) male and female Carex dioica
Any other look-alikes I should mention?
Links to other pages