60 to 65 degrees F.
That is the fundamental relationship between germination and temperature. For every species of seed, there is an optimal soil temperature for germination, and at that temperature, the maximum number of seeds will germinate and in less time than at any other temperature. As a general rule, seeds will germinate indoors where the soil temperature is held constant. In nature, the soil temperature is usually lower at night. Therefore, an indoor drop in temperature at night of less than 10ºF will not significantly delay seedling emergence. For most crops, there is a temperature range just above the minimum germination temperature where the rate of germination is reduced. Spring seeding should not begin until soil temperature at seeding depth reaches or exceeds the required minimum. Shallow depths warm up first.  (Taken from Primroses Quarterly, Spring 2007 Vol. 65 No. 2, pages 8-10). Growing primulas from seed is rewarding for several reasons: seed packets are an economical way to produce a large number of plants; seeds are often the only way to acquire some primula species; and finally, seed growing can be quite dramatic. Yes, dramatic! They are liberal self-sowers, spreading their own flower seed, so after they are done blooming. How To Grow Evening Primrose From Seed: To sow Evening Primrose seeds outdoors, prepare weed-free soil and loosen the top 1 - 2 inches. Spread the flower seed and rake them into the soil only lightly covering. Sow Oenothera Primrose seeds in early spring or late fall.  Temperature is key when it comes to getting seeds to germinate. Pepper seeds require the right combination of heat and dampness to get the growing process started. Cold temperatures slow germination and, when too cold, will prevent germination from happening at all. At the optimum temperature, pepper seeds germinate and sprout within eight days. The best way to control soil temperature when planting pepper seeds is to use a seed starting flat and a heating pad. Sow primrose seeds between late summer and early spring. Primula, or primrose, is a perennial herb plant hardy in U.S. Department of Agriculture zones 5 through 9. The plants do well in cool temperatures with rich soil and can be grown in gardens, woodland areas, flower beds and greenhouses. Cultivation of primrose is typically done through root division and transplant or germination from seeds. Seeds can be harvested from existing plants or obtained from nurseries. The seeds are very small and a time investment is needed to complete the germination process 1 Some seeds germinate when the soil is cool 28-40 F (-2 - 4 C), and some when the soil is warm 76-90 F (24-32 C). 2  Some seeds require exposure to cold temperatures (vernalization) to break dormancy. 3  Some seeds in a dormant state will not germinate even if conditions are favorable.  Germination Temperature for Peppers. Pepper seeds require a temperature range between 65 and 95 degrees Fahrenheit. The optimum temperature for germination is 85 degrees Fahrenheit. At the optimum temperature, pepper seeds germinate and sprout within eight days. The best way to control soil temperature when planting pepper seeds is to use a seed starting flat and a heating pad. Step 2. Place 2 to 3 primrose seeds onto the surface of the soil, press them into the soil to a depth of approximately ¼ inch. Avoid covering the primrose seeds with any soil. Light is necessary for primrose seeds to germinate. Ideal temperature is 60 to 65 degrees F. Germination is between 10 and 30 days. Once seedlings emerge, remove the plastic wrap. As soon as they reach 1 inch in height, remove all but one seedling per pot, or cell. Step 5. Check on the primrose seeds daily. Add water when needed; enough to keep the soil in the planting receptacles moist. Ideal temperature is 60 to 65 degrees F. Germination is between 10 and 30 days. Once seedlings emerge, remove the plastic wrap. As soon as they reach 1 inch in height, remove all but one seedling per pot, or cell.
http://tomclothier.hort.net/page11.html http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex1203 http://www.americanprimrosesociety.org/increase/growing-primula-from-seed https://www.outsidepride.com/seed/flower-seed/primrose/primrose-evening.html http://homeguides.sfgate.com/temperature-peppers-germinate-46236.html http://homeguides.sfgate.com/grow-primulas-seed-45829.html https://en.wikipedia.org/wiki/Germination http://homeguides.sfgate.com/temperature-peppers-germinate-46236.html http://www.gardenguides.com/83753-grow-primroses-seed.html http://www.gardenguides.com/83753-grow-primroses-seed.html
What temperature is required to germinate primrose seeds