7 Causes Of Jalapenos Turning Black – Explained

Jalapenos are traditionally harvested while deep green to capture their famous moderate heat yet however they do go through a spectrum of colours during the ripening process. So, a black jalapeno may not be cause for concern…

But be warned, there are also a variety of more ominous reasons why your jalapenos might be turning black so I will try and help you to identify these so you can spot the difference between a healthy, ripening black jalapeno and anything more sinister!

Reasons For Jalapenos Turning Black

If you picture a jalapeno you likely have an image of a glossy green pepper topping off a delicious Mexican feast. Or maybe you prefer your jalapenos at the end stage of ripening when they are red and smoky?  

Bowl of jalapeños
Credit: Geo Lightspeed CC by SA 4.0

But between these two stages, jalapenos go through a gamut of colours which sometimes includes a patchy black just before they ripen to red. So, if your plant looks otherwise healthy, black jalapenos are likely nothing to worry about and if left another week will reward you with beautiful red fruit.  

Yet although they are reasonably easy to cultivate, jalapenos can suffer greatly from improper watering, adverse weather and pests and diseases, all causing much bigger issues that will often result in black marks appearing. Here are a few more common problems I have come across.

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Jalapeno Plant Diseases

Jalapenos can be struck by a variety of diseases, some more common than others but all resulting in the fruit appearing to turn black.

1. Blossom End Rot

One common reason for jalapenos to have black spots is blossom end rot. It can be common in all pepper varieties and is caused by a calcium uptake issue that is linked to over-watering. It often strikes early in the season when the first few peppers start to appear on the vines. The affected peppers will have large, black or brown spots at their tip.  

Luckily it is possible to prevent blossom end rot by watering consistently and ensuring the pepper plant avoids long periods of drought than heavy watering. If you live in an area of sporadic rainfall this could be the cause, so make sure you have well-draining soil.

Mercifully, blossom end rot does not spell the end for your jalapenos and you can just cut around the black spots and still utilise them.

2. Mosaic Virus

Mosaic is a viral disease that is spread by aphids, so once infection occurs, there is no real cure as the disease is transmitted quickly and plants are already infected by the time you notice and can apply an insecticide.  

The telltale signs are stunted plants with leathery leaves that have a mosaic-like appearance consisting of dark and light spots or streaks. This pattern will often appear on the actual jalapeno too.  

Prevention is key and tackling any sign of aphids in your garden early in the season with insecticidal soap spray or like is key. If you know you have an ongoing aphid issue you could try planting trap crops nearby, like dill or nasturtiums to draw them away or repellent crops like onion or garlic to fend them off.

3. Black Rot

Black rot affects fully ripened jalapenos so if the pepper was red but then has turned black (in contrast to the normal ripening cycle of green to black to red) then there is an issue! It can be distinguished from blossom end rot as it will cover a much larger part of the pepper. Black rot rears its ugly head from excessive watering or a period of heavy rain causing too much moisture around the plant.  

The simplest solution to prevent black rot is to pick your peppers at the green stage or as soon as they start to turn red.  I also advise watering directly into the soil at the base of the plant once the peppers start to ripen.

4. Anthracnose Infection

Anthracnose infection is a fungus that causes watery bruises that can appear on the leaves, stem and the peppers themselves. The bruises will go on to become black spots. You can distinguish this issue from blossom end rot as the infected areas tend to present on the side of the pepper.  The bad news is there is no real way to correct an anthracnose infection as it is often embedded in the seed. Always ensure you buy seeds from a reputable source and discard any plants immediately that you suspect may be suffering.

5. Phytophthora Blight

Also known as pepper plant blight, phytophthora can manifest in many different ways. Seedlings infected with phytophthora will just die shortly after emergence, but if it appears in older plants they will continue to grow but they will develop dark brown lesions near the soil line and it will cause sudden wilting.

If the plant does survive to the point of bearing fruit then you will notice the jalapeno turn black and shrivel.
This blight is common in wet areas with warm soil temperatures creating an ideal breeding ground for the fungus. Once a plant has phytophthora there is no real cure so again, prevention is key.

Pest Infestations on Jalapenos

Several varieties of beetle can attack jalapeno pepper plants, including the flea beetle which at first glance can leave you wondering why your jalapeno has turned black! 

Closer inspection will help you identify hundreds of tiny beetles feeding from the plant although it is rare for it to get to this stage as beetles tend to impact when jalapeno plants are just seedlings. Using row covers or mulch to protect seedlings will offer some prevention and sticky traps can eliminate beetles too.

Pest varieties of worms can wreak havoc on jalapeno pepper plants. Wireworms are particularly troublesome during the seedling stage as they feed on roots whereas tomato fruitworms and beet armyworms appear much later when the plant is maturing – leaving black markings on the pepper.  

All of these worms can be controlled by picking them off plants by hand and by attracting beneficial insects to the garden that eat these worms, like lacewing.

Other Reasons Jalapeno Peppers Turn Black

It is not always caused by panic if your jalapeno is turning black and often just indicates the ripening process has started. Some jalapenos are just naturally dark in colour due to high levels of anthocyanins in the plant’s tissue making them turn a very dark purple shade. Many pepper connoisseurs prefer to source seeds that will produce this purple, almost black jalapeno for its distinct flavouring.

6. Natural Ripening Process

Not all jalapenos will go through a black stage before turning to red or you may miss that stage entirely if you don’t check on your plant for a day or two. If you harvest a jalapeno while it is in the patchy black stage then hopefully it will continue to ripen off the vine to read.

7. Sunburn

Most large pepper varieties will hang down below the plant’s leaves as they grow, and the foliage provides shade. When the skin of the pepper is exposed to direct sunlight, it may develop sunburn which can appear as black scorch marks. Exposed peppers can become seriously burned, softening the skin and inviting mould to grow so try to keep the peppers shaded by leaves whenever possible.  

Verdict: Jalapenos Turning Black

Most of the time a black jalapeno is perfectly natural and if your plant looks otherwise healthy, then fingers crossed, it is just a stage in the ripening process. But if you notice insects, random patches of discolouration or other marks on the leaves or stalk you should act quickly and revisit this guide to identify the issue in an attempt to protect your crop.