You can plant jalapeno pepper (Capsicum annuum “Jalapeno”) seeds gathered directly from a pepper, but it needs to be ripe, and you need to dry the seeds correctly to allow them to germinate. A immature, green jalapeno pepper bought at a grocery store won’t get any riper. The plant yielded by jalapeno seeds gathered from a pepper depends upon the parentage of the seed.
The Pollen Issue
To produce viable seed, jalapeno flowers should receive pollen. A single jalapeno plant can pollinate itself. If bees or other insects transfer pollen from cayenne (Capsicum annuum “Cayenne”) or alternative Capsicum annuum cultivar into your jalapeno plant, then it will produce a vigorous hybrid. Jalapeno will even cross readily with habanero (Capsicum chinense “Habanero”) or alternative Capsicum chinense cultivars. It will cross-pollinate sporadically with cultivars of Capsicum frutescens and Capsicum baccatum like Tabasco (Capsicum frutescens “Tabasco”) and Aji Amarillo (Capsicum baccatum “Aji Amarillo). It will not cross-pollinate at all with Manzano (Capsicum pubescens “Manzano”) or alternative infrequently cultivated Capsicum pubescens cultivars. Pepper plants should be planted at least 400 feet apart to prevent cross pollination. The practical meaning of the pollen issue is that in case you collect seeds from a jalapeno hybrid, the result will not likely resemble the pepper it came out of.
Capsicum annuum cultivars will grow as perennials at U.S. Department of Agriculture plant hardiness zones 9 through 11. Capsicum chinense cultivars will grow in USDA zones 10 through 12. Cultivars of Capsicum frutescens, Capsicum pubescens and Capsicum baccatum will develop in USDA zones 8 through 11. Peppers are grown as annuals in colder climates. Jalapenos require a growing period of 80 days to adult. Their growing season should ideally possess night-time temperatures of 70 to 80 degrees Fahrenheit and day-time temperatures of 80 to 90 F with at least 6 full hours of sun.
Jalapenos turn from green to purple to red as they mature. Viable seeds have to come from a fully ripe, red pepper which has started to wrinkle. Since jalapenos will not ripen further once they are eliminated from a vine, it’s not likely that you will locate one in a grocery store. If frost strikes your plant prior to your peppers are fully ripe, hang the plant upside down in a cool, dry place until the peppers are ready for seed collection. If you don’t dry seeds before you plant them, then they’ll decay or gradually deteriorate and die. To dry them, then place them on a paper-covered tray and place them at room temperature out of direct sunlight, and stir them every few days to expose them to air. If you’re able to bend the seeds after a week, then they are not ready. They should be so brittle that they won’t score should you bite them. Store the dried seeds at zip-top plastic bags in a plastic container in the base of the fridge until you are ready to plant them; a temperature between 35 and 50 F is best.
Plant your seeds inside five to six weeks prior to the last expected spring frost. Get a soilless seed germination mix by adding 1 tablespoon of dolomite lime and 2 tablespoons of 5-10-5 or 5-10-10 fertilizer into 1 quart peat moss and 1 quart vermiculite. Plant the seeds 1/4 inch deep in the mix and keep it evenly moist in a temperature between 75 and 85 degrees Fahrenheit. When the seedlings emerge, lower the temperature to 70 degrees F. When the seedlings develop two true leaves, thin them two inches apart. In six to eight weeks, they need to be 5 to 6 inches tall, ready to transplant outdoors in a sunny area when there’s no danger of frost.