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?

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