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 and 60%, while the oil content of the seeds varies between 20 and 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. When temperature and daylength start to increase, the central stem begins to elongate and branch, growing more rapidly. Early sowing allows more time for developing a large rosette and more extensive branching, which results in a higher yield. Flowering is mainly influenced by daylength. The period from the end of flowering to maturity is usually 4 weeks. The total period from sowing to harvest maturity varies with variety, location, sowing time and growing conditions; for June or July sowings, it may be about 26–31 weeks. Both wild and cultivated forms have a diploid set of 2n = 24 chromosomes. Crossings with
Carthamus palaestinus,
Carthamus oxyacanthus and
Carthamus persicus can produce fertile offspring. ==History==