Immature chile peppers are green chiles, and, when left on the plant, they ripen and become red chiles.
The spicy, hot taste of a chile depends on how much capsaicin is produced. The variety of chile plant influences this, but so does air temperature and Gardening practices like fertilizing and watering. Capsaicin is concentrated in the yellow ridges along the inner walls of a chile pepper. The seeds really aren’t hot until capsaicin pustules burst onto them. Hot, dry weather promotes production of capsaicin.
Choose chiles on the basis of pungency. A very mild chile variety is NuMex. NuMex Big Jim or 6-4 are chile varieties with a medium bite. For hot chiles, consider Sandia or Espanola Improved. For the brave, some very hot varieties are Jalapeno and Cayenne.
Plant chile transplants about the last day of May, or when night temperatures consistently remain above 50 degrees Fahrenheit. It’s best not to plant chile peppers where close plant relatives were grown in the last year. These include tomatoes, eggplant, potatoes and tomatillos. The same diseases that affect these plants will affect chile plants and may carry over from year to year.
Space transplants about 24 inches apart and fertilize them with a weak water-soluble fertilizer. Fertilize the chiles again in four weeks. Water chiles regularly through the growing season. Excessive water can cause root disease, especially in heavy clay soils.
Harvest green chiles when the peppers are firm and a glossy green, usually in August. Green peppers left on the plants will turn entirely red and be ready for harvest by late September.
For more information, see the following Colorado State Extension fact sheet(s). http://www.ext.colostate.edu/ptlk/1803.html