Safflower (Carthamus tinctorius) is a highly branched, herbaceous, thistle-like annual plant in the family Asteraceae. It is commercially cultivated for vegetable oil extracted from the seeds and was used by the early Spanish colonies along the Rio Grande as a substitute for saffron. Plants are tall with globular flower heads having yellow, orange, or red flowers. Each branch will usually have from one to five flower heads containing 15 to 20 seeds per head. Safflower is native to arid environments having seasonal rain. It grows a deep taproot which enables it to thrive in such environments. Biology Plant morphology Safflower is a fast growing, erect, winter/spring-growing annual herb, that resembles a thistle. Originating from a leaf rosette emerges a branched central stem (also referred to as terminal stem), when day length and temperature increase. The main shoot reaches heights of . The plant also develops a strong taproot, growing as deep as . First lateral branches develop, once the main stem is about high. These lateral branches can then branch again to produce secondary and tertiary branches. The chosen variety as well as growing conditions influence the extent of branching. The elongated and serrated leaves reach lengths of and widths of and run down the stem. The upper leaves that form the bracts are usually short, stiff and ovate, terminating in a spine. Buds are borne on the ends of branches, and each composite flower head (capitulum) contains 20–180 individual florets. Depending on variety, crop management and growing conditions, each plant can develop 3–50 or more flower heads of diameter. Flowering commences with terminal flower heads (central stem), followed sequentially by primary, secondary and sometimes tertiary branch flower heads. Individual florets usually flower for 3–4 days. Commercial varieties are largely self-pollinated. Flowers are commonly yellow, orange and red, but white and cream coloured forms exist. The dicarpelled, epigynous ovary forms the ovule. The safflower plant then produces achenes. Each flower head commonly contains 15–50 seeds; however, the number can exceed 100. The shell content of the seeds varies between 30-60%, the oil content of the seeds varies between 20-40%. Plant development Safflower usually emerges 1–3 weeks after sowing and grows slower under low temperatures. Germination of safflower is epigeal. The first true leaves emerging form a rosette. This stage occurs in winter with short daylength and cold temperature, as the safflower can tolerate frosts up to during the rosette stage.