Virginia Tech Weed Identification Guide

Common or Asiatic Dayflower: Commelina communis

Weed Description:  An erect or more often creeping annual monocot often mistaken for a broadleaf weed due to it's attractive blue flowers. Usually only found in shady and/or damp areas and most often a weed of landscapes and nursersies.
Leaves:  Leaf blades are lanceolate in outline with parallel leaf veins and often have hairs on both the upper and lower surfaces.  Leaves are 2-4 inches long, 2/3-1.5 inches wide, and lack petioles and ligules. Leaves clasp the stem at the base and hairs are often present in this area.

Stems:  Thick, reaching 2 1/2 feet in length, swollen at the nodes, and often rooting when nodes come into contact with soil.

Roots:  Fibrous root system and plants often root at the nodes when in contact with the soil.

Flowers: Occur on long flower stalks arising from the region between the stem and leaf (leaf axils).  Flowers consist of 2 blue petals and 1 white petal.  Each flower will appear for only one day.

Fruit: A two-celled capsule. 

Identifying Characteristics:   Prior to flowering, this weed is often misidentified as a common grass weed of landscapes or nurseries.  For example, Deer-tongue Grass (Panicum clandestinum) is very similar to common dayflower in both appearance and growth habit.  However, the lack of ligules and attractive blue and white flowers help to distinguish this weed from most grasses.