Sunflower seeds will germinate at temperatures as low as 39 degrees Fahrenheit.
Sunflower seeds will germinate at temperatures as low as 39 degrees Fahrenheit. The optimum temperature for sunflowers is between 70 and 78 degrees Fahrenheit.  Temperature. Sunflowers germinate best at a soil temperature of 70 to 85 degrees Fahrenheit. Outdoor planting time is typically several weeks after the last spring frost when the soil has warmed thoroughly. Sunflower seeds are planted one-half inch deep. Because sunflowers are an oil-rich seed, they require slightly more water for germination than many other seeds. This requires watering the ground thoroughly outdoors after planting and not allowing the soil to dry out completely until germination occurs. Check the outdoor temperatures. While sunflowers can be started indoors, they work best if they're moved outdoors within a week. They grow best at temperatures between 64 and 91ºF (18–33ºC), but you can give it at lower temperatures, once the last frost has passed. Sunflowers are annual plants that produce large or small yellow flowers in the summer. Sunflowers are very popular because of their beauty, and because they are easy to grow. Planting sunflower seeds in the spring can be a fun activity for adults and children. 1 Temperature influence on growth – Seeds of cool season crops germinate at 40°F to 80°F. Warm season crop seeds germinate at 50°F to 90°F. 2  In the spring, cool soil temperatures are a limiting factor for plant growth. 3  In mid-summer, hot soil temperatures may prohibit seed germination.  Temperature. Sunflower seeds only germinate in warm soil. Soil temperature must be over 50 degrees Fahrenheit for seeds to germinate and for plants to grow. Soil sometimes warms more slowly than air temperatures, so when in doubt wait an additional week to plant or use a soil thermometer to verify the soil temperature. Sowing Tips. Seeds usually germinate within seven to 10 days after planting if the proper weather conditions are met. Sunflowers germinate and grow best when sown directly in the flower bed, although it is possible to start them in pots indoors in areas with a short optimum growing season. Overview. Sunflowers are tall, beautiful flowers that perk up any garden or lawn, and their seeds make a heart-healthy snack. Sunflower seeds need a temperature of approximately 70 degrees Fahrenheit to begin germination and sprouting. Maintaining the soil temperature at 70 degrees can be difficult, especially if you live in an extremely warm or cold climate. However, sunflower seeds can be germinated without soil in your own home.  Comments. Submit. Sunflowers are tolerant of both hot and cold temperatures, but do better in cooler weather. According to Purdue Extension, sunflower seeds will germinate at temperatures as low as 39 degrees Fahrenheit, but the ideal temperature would be at least 46 to 50 degrees Fahrenheit. The best temperature for growing plants, however, is between 70 to 78 degrees Fahrenheit Indoors, a heating mat under the pots can raise the soil temperature to at least 70 F. The seeds will sprout in 10 to 14 days outdoors. Indoors, where the growing environment can be more closely controlled, germination often takes place in six to 10 days. Sunflower seeds do not require light for germination. Sunflower seeds are planted one-half inch deep. Because sunflowers are an oil-rich seed, they require slightly more water for germination than many other seeds. This requires watering the ground thoroughly outdoors after planting and not allowing the soil to dry out completely until germination occurs. If the soil temperature is not right, your seeds may fail to germinate. Both the seedlings that do sprout, and your garden transplants, can become stunted, or even die. For the absolutely best start to your garden season, plant your vegetables, both seeds and seedlings, when the soil temperatures are optimum to do so. 
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best temperature for sunflower to germinate