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Description of the Plant

Safflower is one of a larger genus of thistle-like plants originating in the Mediterranean and Middle Eastern regions of the world. In California it grows to a height of 1.5 to 6 feet (0.4 to 2.0 m), depending primarily on the planting date and plant spacing. Late planting and lower populations reduce plant height. The plant can produce many branches, each with a terminal flower head. Each head is a dense capitulum with 20 to 180 flowers. Surrounding the flowers are bracts, which are modified leaves. The flowers are tubular and are attached to a flattened receptacle. There are bristles or hairs interspersed among the flowers. Each flower can produce a seed if conditions are favorable.

Branching depends on plant population and sowing date (figure 4) and environmental factors like moisture supply. Depending on its location on the plant, and on crop management and environmental conditions, individual flower heads produce from 20 to 100 seeds. Weight per bushel varies from 39 to 46 pounds, depending upon crop growth conditions and variety. Safflower varieties grown in California vary in oil content but most are greater than 40% oil and 15% or more protein. The remainder of the seed consists of fibrous constituents, carbohydrates, and ash. Hulls make up about 35% to 38% of seed dry matter.

The flower color varies with variety, from red through orange and yellow to white. Commercial varieties grown in California are yellow. On drying, these turn yellow to red. The seeds (achenes) of present California varieties have white to cream or sometimes light brown hulls, which can appear striped and are shaped like small sunflower seeds. Varieties grown for birdseed, primarily in the Midwest and Canada, are white even though color has no effect on birdseed quality or bird preferences. Commercial varieties of safflower have spines on the leaves and the modified leaves associated with flower heads (the involucre). The spines develop late, as the plants form flower heads. A less thorny variety (UC28) is sometimes grown for dried flowers and is white seeded.

Plant development

Safflower requires a minimum of about 120 days to produce a crop, but 140 to 170 days is more common for March planted crops, and allows for sufficient time for seed moisture to reach 8%, the level required for harvest. The development stages of safflower are depicted in figure 3.

Days since emergence	0	30	50	62	75	100	150
Stage	Emerg- ence	Rosette	Stem elongation	Initial branching	Full branching	Flowering	Maturity
Yield Component			Bud & floret formation	Flower petal formation	Stamen, pistil & pollen formation	Fertilization	Seed maturation
Root development
Rust
Phytophthora root rot
Thrips & lygus bugs
Figure 3. Development stages of safflower and corresponding susceptibility to selected pests and diseases. Susceptibility is indicated by the thickness of the bar and is meant to be illustrative rather than quantitative.

Safflower emerges at soil temperatures above 40° F (4.4° C) but emergence is much more rapid at temperatures of 60° F (15.5° C) or greater. Emergence at minimum temperatures is slow, requiring up to three weeks. During late spring, germination occurs rapidly and seedlings appear three to four days after planting at normal depth. After emerging, seedlings develop a number of leaves but remain low growing, forming a modified rosette. Stem development and elongation is influenced by increasing day length and increasing average temperatures. In a test under greenhouse conditions at approximately constant temperatures, increasing day length from 10 to 14 hours shortened the average length of the rosette stage from 39 to 23 days for a group of six different safflower genotypes. If sown in late fall in California, (October or November), the plants will remain in the rosette stage for two or three months, but when sown in late spring (late April or early May) this stage may last less than four weeks. Fall sowing is not recommended in California.

At Davis in the southern Sacramento Valley (38.5° N latitude), stem growth starts the latter part of March in safflower sown during late winter or early spring, and about the end of April when sown during the first part of March. In the San Joaquin Valley and southern California, stem growth begins in early March if the crop is planted in December or January. Once it begins, stem growth is rapid.

Branching begins from the central stem when the plant is 8 to 15 inches (0.2 m to 0.4 m) tall. Each primary stem branches to form one to five (or more) flower heads. Wide plant spacing and early planting dates increase branching and bud formation (figure 4). For example, a plant sown in November may reach six feet tall (1.9 m) and have over 50 viable flower heads, while the same variety planted in April may only reach 18 inches (0.45 m) and have three to five flowers. Depending on date of planting, safflower reaches its full height varying from 18 inches to 5 feet or more (0.46 m to 1.5 m) at the time it flowers. Buds open into blossoms within four to five weeks after they appear.

Figure 4. Plant density and branching patterns. Primary, secondary, and tertiary buds are indicated. Source: Adapted from Weiss 1971.

Flowering dates are remarkably consistent. At Davis when safflower is planted at intervals from November to March, all plantings will mature over a range of about 10 days in early August. Maturation in the southern San Joaquin Valley occurs one or two weeks earlier. Individual seeds are physiologically mature in about 25 days after flowering. Within a head, however, the flowering and maturing of individual florets and seeds occurs over a period of up to 7 days. Because of the variation among florets, all the seed in a flower head is physiologically mature from 35 to 40 days after the peak of flowering. Safflower should be harvested at moisture content of 8% or less. Even though seeds may be physiologically mature sooner, in California, 50 to 60 days from peak flowering commonly are required to reach this moisture content.

Despite being an annual, safflower is among the deepest-rooted of all crops. Safflower roots have been found to a depth of 12 feet (3.7 m) at Davis on a deep, well-drained Yolo loam soil. Other research trials have documented substantial water depletion by safflower roots at 10 feet (3 m) in a permeable soil. The depth of root penetration influences the amount of water available to the crop. Soils vary in permeability and depth and this variation will influence the depth of root penetration. When safflower is sown late in the season, it will not develop as deep a taproot by the time it flowers as it does when planted earlier, effectively reducing the available water supply.

Safflower Contents | Climate Requirements [4]

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Modified: 28 May 1999 Comments to webmaster@agric.ucdavis.edu