Cilantro, a widely used herb, requires specific temperature conditions for successful growth and optimal flavor development. Understanding these preferences is important for gardeners. The plant’s sensitivity to temperature directly influences its growth cycle and the quality of its aromatic leaves.
Ideal Temperature Range for Cilantro
Cilantro thrives in cool environments, preferring air temperatures between 50 and 85 degrees Fahrenheit (10 to 29 degrees Celsius) for robust leaf production. Temperatures within this range allow the plant to grow steadily, producing lush foliage. Soil temperature is also a factor, with seeds germinating best when the soil is between 55 and 68 degrees Fahrenheit (13 to 20 degrees Celsius). This cool preference classifies cilantro as a cool-season crop, performing well in spring and fall.
Cilantro and Heat Stress
High temperatures significantly impact cilantro, often leading to a process known as bolting. Bolting refers to the plant prematurely producing a flower stalk and setting seeds, rather than continuing to grow leafy foliage. This response is triggered by rising temperatures, typically when air temperatures exceed 70 to 75 degrees Fahrenheit (21 to 24 degrees Celsius). As the plant focuses its energy on reproduction, its leaves become smaller, more lacy, and develop a bitter or less desirable flavor. Heat stress also causes stunted growth and a decline in plant vigor, and once bolting begins, the quality and quantity of edible leaves diminish significantly.
Cilantro and Cold Tolerance
Cilantro exhibits cold tolerance, but is sensitive to extreme cold and frost. It can withstand light frosts and temperatures down to the low 40s Fahrenheit (around 4-5 degrees Celsius). Some varieties may tolerate temperatures as low as 10 to 25 degrees Fahrenheit (-12 to -4 degrees Celsius) if protected. However, extended periods of freezing temperatures, especially below 28 degrees Fahrenheit (-2 degrees Celsius), can cause damage or kill the plants. While cold can slow growth and potentially lead to leaf discoloration, light frost can sometimes make cilantro leaves sweeter by encouraging the conversion of starches to sugars.
Strategies for Temperature Management
Effective temperature management ensures a sustained cilantro harvest. To mitigate heat stress, plant cilantro in early spring or late summer to grow during cooler periods, avoiding intense mid-summer heat, and provide afternoon shade to delay bolting. Regular watering is also beneficial, as moisture stress can accelerate bolting. Choosing “slow-bolt” or “long-standing” cilantro varieties can extend the harvest window. Additionally, succession planting, where new seeds are sown every few weeks, ensures a continuous supply of cilantro leaves as older plants bolt.
Protecting cilantro from cold involves measures such as using row covers or cold frames, which shield plants from frost. Mulching around the base of the plants helps insulate the soil, moderating soil temperature and protecting roots from cold. In regions with mild winters, cilantro planted in the fall can often overwinter and provide a spring harvest. For short-term cold snaps, covering plants with blankets or tarps overnight can offer protection.