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Climate Requirements

Atmospheric humidity. In early growth stages, safflower is tolerant of high atmospheric humidity, but after flower buds form, prolonged rain or fog will cause Botrytis head rot to appear on the buds or flowers. There are no resistant cultivars and the disease cannot be controlled economically. This disease inhibits the production of commercial varieties in coastal areas of California. Another disease caused by rain late in the development of the crop, Alternaria, is rare in California but seriously limits safflower production east of the Rocky Mountains and in other locations worldwide. High relative humidity in early spring encourages the development of rust. Because of these and other disease limitations, safflower production is limited to locations having a rain- and fog-free climate during most of the growing season, particularly in the late summer and early fall.

Temperature. The frost resistance of safflower depends upon the variety, stage of development, and plant density. In the seedling stage most varieties will tolerate temperatures as low as 20° F (-7° C), and some experimental lines have been reported to withstand a temperature of 10° F (-12° C). Seedlings spaced 3 to 4 inches (7.5 cm to 10 cm) apart are reported to survive low temperatures better than those spaced more closely, though it is not clear why this should be so. Once stems have begun to develop, safflower becomes more sensitive to frost damage, and temperatures of 25° F (-4° C) will damage the varieties used in California. In the bud stage or after flowering begins, any temperature below 32° F (0° C) will cause damage to the developing flowers or seeds.

If soil moisture is adequate, safflower tolerates the high summer temperatures (100° to 115° F; 38° to 43° C) of the Sacramento and San Joaquin Valleys. Because it is difficult for plants to recover enough water from the soil when they are exposed suddenly to high temperatures, even when soils are moist, yields generally are highest in years when daytime temperatures at flowering and immediately thereafter are moderate (75° to 90° F; 24° to 32° C).

Wind. Safflower does not lodge or shatter under the normal range of wind velocities occurring in the Central Valley and inland coastal foothills where it is grown in California. If plants have become very tall due to early planting and long periods of vegetative growth, some lodging may occur. Seedling rust may cause affected plants to lodge later in the season.

Safflower Contents | Water Use [5]

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Modified: 7 Jun 1999 Comments to webmaster@agric.ucdavis.edu