Growing Poblano Peppers in a Greenhouse [Solving 3 Common Problems]

Greenhouses have really changed the game for growers all over the world. But are poblano peppers a good plant to grow?

Poblano peppers are perfect for growing in a greenhouse. Keep temperatures 70-85°F during the day and above 60°F at night. Since they’re an indeterminate species, under the right conditions greenhouse gardening allows you to grow poblano peppers for years to come. Use a heated greenhouse in cold temperature climates to enjoy some winter poblanos!

Read on for the best how-to guide on the web about growing poblano peppers in a greenhouse!

Do poblano peppers grow well in a greenhouse?

Poblano peppers are warm-weather plants that require temperate heat and full sunlight. Are they a good choice for growing in greenhouses?

Poblano peppers grow well in a greenhouse. Peppers enjoy moderate heat and lots of sun, which greenhouses are great at! Greenhouses allow you to grow poblano peppers all year round. Since poblano peppers are indeterminate under the right conditions, you can get yields for years.

If you want to learn how to grow your own epic poblanos in a greenhouse, keep reading!

How to grow poblano peppers in a greenhouse

Poblano peppers are relatively easy to grow under the right conditions; however, there are slightly different concerns when growing in a greenhouse.

Here are some things to consider when growing poblano peppers in a greenhouse:

  • Greenhouse structure
  • Germination
  • Prune and train
  • Pollinate

Let’s take a look at each of these considerations.

Greenhouse structure

Your choice of greenhouse structure depends heavily on your growing zone, your budget, and whether or not you want to grow year-round. 

Some options include:

  • High-roof passive ventilation greenhouses
  • Deep winter greenhouses
  • Heated greenhouses

Let’s discuss three common types of greenhouse structures!

High-roof passive ventilation greenhouses

These greenhouses are great for tropical and subtropical climates due to their inventive ventilation systems.

High-roof passive ventilation greenhouses are good for tropical and subtropical environments. They can be up to 80% cheaper per square foot than traditional greenhouses. They utilize polyethylene, insect screens, and passive ventilation.

There are currently trends in Florida towards high-roof greenhouses with passive ventilation. These are covered with polyethylene which gets replaced every couple of years. It absorbs UV and avoids water condensation.

Insect screens cover the vents and side walls. These greenhouses are cheaper and are great for tropical and subtropical environments. In fact, passively ventilated greenhouses can be up to 80% cheaper per square foot!

Deep winter greenhouses

Deep winter greenhouses are one of the coolest kinds of greenhouses out there!

Deep winter greenhouses are optimized to be as environmentally friendly as possible. They use solar power to heat the greenhouse. The hot internal air is blown underground to be stored in rocks, creating a store of thermal energy to be employed at night.

Up north, deep winter greenhouses (DWG) are designed to limit fossil fuel usage during the freezing winter months. They use solar power to heat the unit.

DWGs are situated east to west, with a wall of solar panels facing south. This wall is specifically calibrated to get the most solar energy possible, even when temperatures are freeze-your-sweat low.

DWGs are quite the invention. The sun heats the internal air. The air gets blown underground and – get this – stored in rocks! These heated rocks create thermal energy that can be used at night.

While DWGs are best for plants that don’t need much light, the addition of artificial lights makes them perfectly suitable for poblano peppers.

Heated greenhouses

You’re likely familiar with heated greenhouses, but let’s go into some more detail.

Heated greenhouses can use electricity, wood, LP gas, or natural gas for heat sources. You need to consider how much heat you’re losing due to conduction, convection, and radiation in order to calculate the amount of heat to supply your greenhouse. States as far south as Georgia rely on heated greenhouses in order to grow plants year-round.

Some heat sources used for greenhouses include electricity, wood, LP gas, and natural gas. 

Conduction, convection, and radiation cause heat loss. You can figure out how much heat your greenhouse needs by using a heat loss equation with these three factors.

Heated greenhouses are necessary for lots of places to grow crops all year round – even as far south as Georgia!


Now that you know about a few different kinds of greenhouses, let’s talk about how to germinate your poblanos. After all, you won’t have any plants unless you get this step right!

Poblano peppers germinate in temperatures between 70 and 80°F. You can germinate any time you please if you’re growing in a heated greenhouse. However, in subtropical or tropical environments, you should follow standard planting procedures to avoid flower drop during the hot summers.

When you choose to germinate your poblano peppers depends heavily on where you live and what kind of greenhouse you’re using. For example, you can germinate your peppers in the dead of winter in northern Maine so long as you have a well-heated greenhouse!

Poblanos need temperatures between 70 and 80°F during the germination process. So long as you have those conditions, you’re free to germinate.

If you’re growing in a subtropical or tropical environment, keep in mind that poblanos will start to drop their flowers when temperatures reach above 90°F. This means you’ll want to follow the guidelines of a typical growing season and germinate in the fall.

Prune and train

Pruning and training your poblanos will keep your greenhouse in order while simultaneously encouraging more fruit production! Sounds like a win-win to me.

Two common ways to prune and train poblano peppers in greenhouses are to use the Spanish system or the Dutch V system. The V system creates poblano plants that have two main stems. On the other hand, you don’t prune at all with the Spanish system.

Because greenhouse peppers are often indeterminate, it’s vital to support them vertically. Two common ways to support poblano peppers are with the Spanish system or the Dutch V system.

The V system is the process of pruning a plant so that it has two main stems. These stems are held up with twine. It’s a common system among Canadian and Dutch growers.

Meanwhile, the Spanish trellis isn’t pruned. Rather, the poblanos are supported by poles that have horizontal twine between them. This reduces labor by a minimum of 75%!

Yield numbers are comparable no matter which system you choose to use. That being said, the Spanish system encourages larger peppers and tends to have less blossom-end rot.


You won’t have any peppers without pollination!

While poblano peppers are self-pollinating, it’s worth getting bees to increase the likelihood of high-quality fruit production. This is extra noteworthy during the colder months when pollen viability drops.

Poblano peppers self-pollinate, but utilizing bees in your greenhouse will increase the chances of high-quality peppers. This is specifically important when it’s colder out because pollen viability will be lower.

Bumblebees subsist off of pollen and nectar and naturally know when it’s time to fertilize the peppers. Having a hive reduces the need to pollinate by hand.

Colonies can be expected to live for 2-3 months.

Pro tip: Keep them in the shade during the summer and in the sun during the winter!

How to solve common greenhouse poblano pepper plant problems

You’re bound to run into some problems when gardening no matter how prepared you are. Despite the controlled conditions, this is also true for greenhouse gardening.

Common greenhouse poblano pepper plant problems include:

  • Excessive humidity
  • Brown spots
  • Pests

Let’s talk about how to remedy each of these problems!

Excessive humidity

A little humidity is good, but excessive humidity is a no-go for your poblanos.

Excessive humidity can lead to fungi, mold, and mildew on your poblano peppers. Provide proper ventilation by opening up a panel and/or getting a fan.

Too much humidity can encourage fungi, mold, and mildew on your poblano peppers. 

Likewise, the same problems can arise if your leaves stay wet throughout the day. Drip irrigation is a good solution if you find that your watering system is causing your leaves to never dry off.

The best way to combat humidity is to provide proper ventilation. You can start by just opening up a panel, but if you’re still having trouble, consider getting a fan!

Brown spots

Brown spots are never a joy to discover.

Different kinds of brown spots on poblano peppers include:

  • Bacterial leaf spot
  • Blossom end rot
  • Anthracnose fruit rot
  • Cucumber mosaic virus (CMV)
  • Sunscald

Each type of brown spot has a different cause. 

For example, sunscald can be caused by excessive pruning and subsequent overexposure to the sun. Meanwhile, calcium deficiencies can lead to blossom end rot.

Even worse, some brown spots can lead to further problems. Bacterial leaf spots can leave fruits susceptible to pathogens, causing even worse damage.

To learn how to treat bacterial leaf spots, check out our guide about all-things brown spots!


Pests can ruin everything!

Pests are drawn to humidity and warmth. Unfortunately, greenhouses are often overly warm and humid if not well managed! Follow safety guidelines when using pesticides in an enclosed area such as a greenhouse. You can also utilize biological control agents, which are part of an exciting field of research.

Warmth and humidity are two things that pests love. Unfortunately, this can spell disaster if you’re not managing your greenhouse well!

Pests problems will usually persist indefinitely unless you take care of them. Early detection is vital, so constant monitoring is highly recommended.

While you can use pesticides, it’s important to follow the guidelines of PAT-4 Greenhouse Pesticides and Pesticide Safety. Using chemicals in an enclosed area can be very dangerous if you don’t know what you’re doing or decide to slack on safety precautions!

When can I put poblano peppers in an unheated greenhouse?

If you have an unheated greenhouse, you may be concerned about whether or not your poblano peppers will grow in it.

You can germinate poblano peppers in an unheated greenhouse when ambient temperatures reach between 70-80°F. If you want to germinate indoors, use a heat mat and begin the process 2-3 months before the last average frost date. Transplant when nighttime lows reach above 50°F.

Poblano peppers germinate best with temperatures between 70-80°F. If you’re planning on using your greenhouse to germinate, wait until ambient temperatures reach that point to begin the germination process.

If you’re germinating indoors, use a heat mat and start germinating 2-3 months before the last average frost date. Then transplant to your greenhouse when nighttime lows reach above 50°F.

What temperature should a greenhouse be for poblano peppers?

Poblano peppers need relatively warm temperatures. What does that translate to when growing in a greenhouse?

Poblano peppers grow best with:

  • Daytime – 70-85°F
  • Nighttime – 60-70°F

The peppers will not grow well in lower temperatures and are likely to scorch in consistently higher temperatures.

How long do poblano pepper plants live in a greenhouse?

Poblano peppers grow to be quite large and can take up a fairly significant amount of space. How long can they live in a greenhouse where the temperature can be controlled?

Poblano pepper plants can live and produce for multiple years in a greenhouse since they’re an indeterminate species under the right conditions.

Indeterminate plants continue to grow and produce throughout their lifetimes, supplying you with a slow and steady yield.

Can you keep poblano pepper plants in a greenhouse over winter?

You can keep poblano pepper plants in a greenhouse over winter so long as you live in a warm climate or the greenhouse is heated.