Greenhouse Growing Guide: Peppers

Native to Mexico and genetically adapted to dry, warm conditions, pepper plants like it hot and sunny. Growing peppers outdoors is difficult because they require a long growing season. Even if your overall summer temperatures are warm enough, your peppers may not have sufficient time to ripen. Starting peppers in a greenhouse 12 weeks before the last frost estimated date provides a headstart, and they can also be grown exclusively in greenhouses. 

Starting Your Pepper Seeds

Getting pepper seeds to break dormancy requires warm soils as well as patience. Even under optimal conditions, some varieties of peppers may take as long as three weeks to germinate, and home gardeners sometimes give up on them before they sprout. Sweet peppers don't take as long as hot peppers, but no matter what type you decide to grow, give your seeds plenty of time. Peppers that are going to be grown in a greenhouse environment should be transplanted into their permanent containers shortly after the first true leaves show in order to promote strong, deep roots. 

Heat and Water

After transplanting your peppers into their permanent containers in the greenhouse, keep daytime temperatures at 73 degrees Fahrenheit and nighttime temperatures at 70 degrees for 10 days. After this amount of time has passed, raise daytime temperatures to 75 degrees and reduce nighttime temperatures to 64 degrees for the duration of the season. 

Overwatering is one of the biggest problems for those growing peppers in a home greenhouse. Too much water stunts the growth of pepper plants and makes soil conditions right for the spread of fungal pathogens. Water when your soil is dry but try to avoid going so long without watering that the plants wilt. However, you'll be able to bring them back if you water deeply. 


Too much fertilizer causes peppers to produce an abundance of green leaves but not many blossoms, which will result in lower yields. Peppers respond best to light feedings with a balanced, water-soluble solution. Once the plants begin to flower, switch to a high-potassium fertilizer to encourage optimal production. Most fertilizers formulated for tomatoes will be adequate for this purpose. 

Pests and Diseases

Aphids are a risk for pepper plants. Even though they won't be quite the problem that they are when the plants are grown outdoors, releasing ladybugs into your greenhouse environment will keep a potential aphid population in check. 

Peppers are fairly resistant to most pathogens, but you may encounter some bacterial spotting as the fruit begins to mature. Regular applications of a fungicide designed for use on peppers should be enough to keep it under control. 


As with tomatoes, peppers have a long flowering season, so the individual fruits mature at different times. Depending on the variety, your hot pepper plants should begin to ripen around 150 days after being planted, while sweet peppers have a shorter time frame of between 60 and 90 days. Visual indications of ripeness vary, but all pepper varieties are ripe when they're easily pulled from the stem. Give it a few more days if you are met with resistance when pulling. 

Overripe peppers should never be allowed to remain on the plant because they take too much energy away from the fruit that's still developing. Certain types of peppers also start flowering again once you start harvesting them, so it's possible to get a small second crop. 

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Using a two-color technology, ArmorClear is formulated for your greenhouse to maximize your plant growth.

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