In the language of flowers, Dahlias represent dignity and stability, as well as meaning my gratitude exceeds your care.
Beautiful red dahlia
Photograph by 
Dahlia facts
Dahlias are annual blooming plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. As a member of the Asteraceae the flower head is actually a composite with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturists.
Dahlia is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
Info source
@gratefulvibes