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The jalapeño pepper (Capsicum annuum “Jalapeño”) is a cultivar of the species Capsicum annum, the most common and extensively cultivated of the five domesticated capsicum or chili pepper species.
The five domesticated capsicum or chili pepper species are:
- Capsicum annum, which includes the jalapeño, bell, cayenne, paprika, ancho, and serrano peppers.
- Capsicum baccatum, which includes South American varieties such as the ají amarillo and lemon drop peppers.
- Capsicum chinense, which includes the habañero, Bhut Jolokia, and Carolina Reaper (the hottest pepper in the world).
- Capsicum frutescens, which includes the Tabasco pepper.
- Capsicum pubescens, which includes the Manzano pepper.
All peppers belong to the nightshade family (Solanaceae), which includes familiar relatives such as tomatoes, eggplants, and potatoes.
Jalapeños originated from wild chilies grown in Central and Southern America. Archeological evidence from Mexico shows that humans have used wild chilies as food as early as ~8,000 B.C. 
Chilies have been used to spike drinking chocolate, added to maize gruel, and were offered to dead elites in Mesoamerica for thousands of years before being introduced to Europeans and the rest of the world by Christopher Columbus in 1493.
Jalapeños were first cultivated in the city of Xalapa, the capital of the Mexican state of Veracruz. The name jalapeños in Spanish means “from Xalapa.”
According to genetic analysis, Jalapeños were bred from serrano peppers, whose gene pools are closely related to the ancestral form of Capsicum annum. 
How Hot are Jalapeños?
The Scoville scale measures how much the capsaicin oil found in chili peppers must be diluted before its spiciness is undetectable by a panel of tasters. The higher the Scoville Heat Unit (SHU), the spicier the pepper.
Jalapeños have a SHU value of between 3,000 – 8,000 SHU.
For comparison, bell peppers have a SHU of 0, serrano 10,000-25,000 SHU, cayenne 30,000 SHU, Thai chilies 50,000-100,000 SHU, habaneros 150,000-350,000 SHU, and the hottest Carolina Reaper at 1,400,000 – 2,200,000 SHU. 
Jalapeño Plant Care
Jalapeño peppers are generally easy to care for plants, but they are heat-loving and require lots of sunshine, water, and nutrition to thrive. Plants can be grown from seedling transplants or seeded directly.
There are many types of jalapeño peppers, with some types having less spiciness than others. Jalapeños are often harvested and eaten when green but will ripen to a red, orange, or yellow color.
Below, we’ll go over everything you need to know about growing delicious jalapeño peppers.
Like most hot peppers, jalapeños grow best in well-draining, slightly acidic pH 6.0-6.8, sandy, loam soil. Mulch around the plant to conserve moisture and reduce weeds.
Consider growing in a raised garden bed if soils do not drain well. Select a site protected from wind, as peppers have shallow roots and brittle branches.
Water deeply and infrequently with ~1-2 inches per week. Use drip irrigation or soaker hose irrigation if possible. Water in the morning to avoid wet leaves in the evening.
In humid climates, a little moisture stress 25-30 days after planting promotes root growth.
Overwatering may cause flowers to drop or blossom-end rot, which causes dark leather brown spots to develop on the fruits.
Jalapeños require full sun (6-8 hours) to blossom and set fruit. Consider some partial shading if temperatures are consistently above 95°F (35°C).
Humidity & Temperature
Jalapeños are warm climate crops, with ideal daytime temperatures between 70-85°F (21-29°C) and nighttime temperatures 50-60°F (10-15°C).
Temperatures below 50°F (10°C) may cause chill damage to crops, and temperatures above 95°F (35°C) may inhibit germination and cause blossom drop and heat stress. 
The ideal relative humidity is between 50-70%.
Most potting mixes will contain about two weeks of fertilizer. If not, prepare the soil with NPK 5-10-10 or 8-16-16 ratio (half as much nitrogen) fertilizers before planting.
Fertilize every two weeks after that and switch to a high potassium 9-15-30 fertilizer once flowering begins.
Although peppers are hungry plants, check for signs of fertilizer burn due to overfeeding, and reduce fertilization accordingly.
Organic farmers can use a combination of fish emulsion, green sand, kelp meal, and bone meal to get similar results.
Diseases & Pests
Jalapeños are susceptible to several diseases, including anthracnose, bacterial spot, phytophthora blight, wet rot, Cercospora leaf spot, southern blight, blossom-end rot, pepper mild mottle virus, tomato spotted wilt virus, among others.
Bacterial spots are the most common, causing fruits to rot as they mature. Apply a copper-based fungicide or bactericide spray every 7-10 days when fruits develop to prevent bacterial rots.
Avoid planting jalapeños and other peppers immediately after planting other susceptible hosts such as tomatoes, beets, beans, and spinach.
Insecticidal soap or horticultural oils such as neem oil will help control pests.
Days to Maturity
Directly seeded crops will be ready to harvest 110-120 days after planting. For transplanted crops, it will take 75-85 days.
Jalapeños planted in the spring will be ready for harvest in June. Fall-planted crops will be ready by October and last until the last frost.
According to the California Poison Control System, jalapeño tree leaves and pepper pods contain capsaicin, solanine, and scopoletin. These chemicals can irritate pets’ stomachs, causing vomiting, diarrhea, and skin irritations. 
Jalapeño Plant Stages
Jalapeño plants can grow to a height of about 2-2.5 ft. (0.6-0.7 m) and a width between 1-1.5 feet (0.3-0.45 m).
Jalapeño peppers have six general stages:
- Germination (0-10 days) – Seeds germinate at ideally 84°F (29°C) and will start to sprout and develop the first true set of leaves. Keep soils moist and provide plenty of bright light if growing indoors.
- Adolescent (10-30 days) – Several sets of true leaves will develop. At this stage, transfer plants out of seed trays and into larger pots or standard potting mix. Plants should now be able to handle more potent fertilizers.
- Growth (30-80 days) – This rapid growth stage requires constant watering and feeding. Prune flower buds at this stage to encourage more leafy growth.
- Flowering (90-100 days) – White or yellow fruit blossoms should be forming. Stop feeding nitrogen-rich fertilizers, and switch to high-phosphorus fertilizers to encourage fruiting.
- Fruiting (100-120+ days) – Successfully fertilized flowers will drop petals and turn into peppers. Fruit will ripen from light to dark green to almost black and finally red. Other varieties will ripen into different colors as well. Keep soils evenly moist, and avoid overwatering.
How to Grow Jalapeño Peppers from Seed
Jalapeños can be grown from seeds from fresh peppers or seed packets.
If growing from fresh peppers, scrape seeds out and let dry for a couple of weeks before planting.
Sow seeds 6-8 weeks before the last frost date in your area if growing indoors. Sow seeds ¼ inch (0.6 cm) into the seed-starting mix or other growing media.
Seeds can be started in germination trays or small containers with holes at the bottom before transplanting to containers or the outdoors.
Place seedling trays or containers on top of a heat mat or refrigerator to encourage germination. Water after seeding, and keep soils moist. Consider using a grow light.
Once several true sets of leaves have formed, seedlings can be transplanted into containers or outdoors. Do not transplant unless soil temperatures are at least 65°F (18°C) degrees.
Growing Jalapeños in Pots
Jalapeños grow well in containers, especially if space is limited.
Use a large pot at least 12 inches (30 cm) in diameter and 14 inches (35 cm) deep. A 5-gallon (18 liters) soil container should help maximize yields.
Use a terracotta pot for better drainage and a quality potting mix that drains well. Water after transplanting from seed trays or smaller pots.
Place containers near a south-, west-, or east-facing window for maximum light exposure.
Harvesting Jalapeño Peppers
Fully mature jalapeños will have firm, glossy green skin with pods about 2-3 inches (5-8 cm long). Harvest when jalapeños turn dark green, but they can also be harvested red for a spicier punch.
For maximum yields, wait until 5-10% of the fruits have turned red before harvesting.
Pulling on jalapeños from the stems may damage fruit or branches. Use garden shears, scissors, or hand pruners to harvest jalapeños.
Jalapeños are sensitive to cold injury, so they should be stored in temperatures above 45°F (7°C).
Ideal storage temperatures are between 50-55°F (10-13°C) in 80% relative humidity, perfect inside your fridge’s crisper. Jalapeños stored in these conditions should last 2-3 weeks.
Slice and freeze jalapeños if storing for longer. Pickling, fermenting, dehydrating, and making a sauce out of jalapeños will keep them longer.
Jalapeño Pepper Varieties
There are many types of jalapeño varieties. A few common jalapeño varieties are:
- Senorita (5,000 SHU) – Peppers grow from green to purple to red. A more mild-tasting version of the standard jalapeño. When smoked, these are called chipotles.
- Fresno Chile (300-400 SHU) – A very mild jalapeño that takes less time to mature. They also do well in warm to hot weather and dry climates with long summers. They were also bred for cold and disease resistance.
- Sierra Fuego (5,000 SHU) – Highly productive hybrid with lots of fruits.
- Mucho Nacho (4,500 – 6,000 SHU) – Fast maturing hybrid that can reach maturity in 68 days. Peppers grow longer, up to 4 inches (10 cm). Flavorful without excessive heat.
- Purple jalapeño (2,500 – 8,000 SHU) – These have a little more sweetness than the typical green jalapeño and mature from green to purple to red. These also produce ornamental purple flowers.
- Yellow jalapeño (Jaloro) (5,000 SHU) – Created by the Texas Agriculture Extension Service in 1992, these high-yielding yellow jalapeños turn orange before red.
- Early jalapeño (2,500-8000 SHU) – These mature two weeks earlier than most varieties at 60-65 days.
- Orange Spice (2,500-8000 SHU) – Created by the New Mexico State University’s Chile Pepper Institute, this pepper is also known as NuMex. A cross between a bell pepper and early jalapeño, this orange jalapeño has a twist of citrus and fruity flavors mixed with traditional jalapeño flavors.
Frequently Asked Questions
No, jalapeños do not grow on trees but rather on the stems of the jalapeño plant. Jalapeño plants can grow to a height of about 2-2.5 ft. (0.6-0.7 m) and a width between 1-1.5 feet (0.3-0.45 m).
Depending on the cultivar, a single jalapeño plant can grow on average between 25-50 pods per plant. However, this also depends on harvest timing and the growing conditions. A single jalapeño plant can produce over 100 pods per season if picked green and considerably less if picked red, as red pods require more time to mature.
Red jalapeños are more mature and, thus, are slightly spicier than green jalapeños. Ripe red jalapeños will produce more capsaicin, the ingredient which gives chili peppers their spiciness. However, the spiciness of red jalapeños will only be slightly spicier than green pods, and it will not be too far outside the plant’s typical spiciness range.
Directly seeded jalapeños will be ready to harvest 110-120 days after planting. For transplanted crops, it takes 75-85 days. Of course, some varieties will take longer, and others will take shorter amounts of time. In general, jalapeños planted in the spring will be ready for harvest in June. For fall planting, the crop will be ready by October and last until the first frost.
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 Pereira-Dias, L., Vilanova, S., Fita, A., Prohens, J., & Rodríguez-Burruezo, A. (2019). Genetic diversity, population structure, and relationships in a collection of pepper (Capsicum spp.) landraces from the Spanish center of diversity revealed by genotyping-by-sequencing (GBS). Horticulture Research, 6(1). https://doi.org/10.1038/s41438-019-0132-8
 Reiners, S. (2021, June 2). Pepper Secrets. Cornell College of Agriculture and Life Sciences. https://cals.cornell.edu/school-integrative-plant-science/school-sections/horticulture-section/outreach-and-extension/pandemic-vegetable-gardening/pandemic-vegetable-gardening-2021-archive/pepper-secrets.
 Carter, A. K., & Vavrina, C. S. (2001). High Temperature Inhibits Germination of Jalapeño and Cayenne Pepper.HortScience, 36(4), 724–725. https://doi.org/10.21273/hortsci.36.4.724
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