Green onions are a great herb to use for lots of savory dishes. I love using them not only because of their distinct flavor but also their crispness and rich green color. But yellowing scallions don’t deliver the same—they’re bland, papery, and unsightly! But why exactly do green onions turn yellow?
Leaves of green onion plants turn yellow because of 1) natural aging, 2) improper watering, 3) low temperatures, 4) insufficient light, 5) high humidity, 6) nutrient deficiency, 7) pest infestation, and 8) plant diseases. Only aging is considered a normal reason for yellowing scallions. All other causes are a sign of a problem.
Welsh onions, bunching onions, spring onions, green onions, scallions—whatever you want to call them—are pretty easy to grow from store-bought bunches with intact roots. But this doesn’t mean you’ll never face an issue while growing them at home. So let’s explore the possible solutions to yellowing green onions!
1. Natural Aging
As green onions age, their older leaves will start to turn yellow after 3–4 months This normal process allows live plants to redirect energy into producing new healthy leaves.
The discoloration will normally start from their tips until the leaves are yellow to the very base. Aside from that, it will also become really dry and soft—almost like crepe paper in terms of texture.
But I do get why yellowing can be off-putting, especially in bunching onions (Allium fistulosum) that don’t grow bulbs.
For the most part, though, yellowing green onions simply indicate that it’s time to thin them out. Doing so will even give you more yield!
It could also mean that your spring onion’s about to set flowers.
Here you don’t have to do anything to your green onion plant. But if you really don’t like the look of its yellowing leaves, just cut them off and add them to your compost pile.
Otherwise, the old dying leave will eventually take on a brownish-gray hue and continue shriveling up until they fall off completely from the plant.
2. Improper Watering
Over and underwatering can cause green onion leaves to become yellow. With too much water, the soil becomes compacted and saturated. Conversely, insufficient water causes stunted foliage growth and discoloration.
Too much of anything rarely ever results in a good ending. Even for green onions, this is true, especially when it comes to water. Admittedly, I made this mistake quite a few times in the beginning as well.
You see when spring onion is kept in waterlogged soil it can also get suffocated and drown as the soil has no “space” for the oxygen to pass and be absorbed by the roots (yes, roots as well absorb lots of oxygen).
Overwatering can also lead to the development of plant diseases—which I’ll be discussing later on.
Lack of moisture, on the other hand, can also cause green onion leaves to start yellowing and wilting. Just like humans, when they get super thirsty, scallions end up turning pale and dry.
But once you give your dried-up green onion enough water, it’ll start growing new luscious, and delicious leave again.
Only give your live green onion plants 1 inch of water every week. If they are kept outdoors and they also receive regular rainfall, you’d need to give them even less water.
The same applies if you have them in a smaller and shallower container, but you’ll need to water them more frequently to keep their soil evenly and consistently moist enough.
3. Low Temperatures
Low winter temperatures that cool the soil green onions are growing in cause their leaves to start turning yellow. When left outdoors with no protection, they can die due to frost as well.
Even if you grow your spring onions in pots, as long as you leave them outside once the cold starts to set in your area, it’s likely going to start becoming yellow all over soon.
Now, you’ve probably thought about this as well since it’s seen in most other plants except evergreens. But I think it’s best that I still discuss this anyway.
Once winter starts—sometimes even before that—plants in temperate areas like the northern US and England go through a period of dormancy. This happens as their environment (mainly temperature) becomes too low for them to thrive.
Similarly, green onions don’t do very well with cold soil. In effect, they lose their deep green color and start going pale, from yellow to ash brown. They fare even worse in damp cold soil when they receive very little light—but I’ll talk more about that in the next section.
After scallions are cut for harvest, they can also lose their rich greenness rapidly. This is true for both sides of the extreme. Regardless if it’s too cold or too hot, cut green onion leaves will become yellow and start decaying in more or less a week.
Bring potted onions from your garden indoors before the first frost date in your area. If you have enough space, keep them in a grow tent when possible. In doing so, you can continue growing and harvesting them for all the scrumptious dishes and soups you make at home!
Discover easy recipes for scallions in our article on the best herbs for soups!
Alternatively, you can opt to shield them from frost and snow outdoors using protective covers like this breathable but water-resistant plant blanket from Amazon.
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4. Insufficient Light
Green onion leaves can start turning yellow from the tips when they don’t receive enough light exposure. This commonly happens during winter or when indoor potted scallions are placed in an area that receives very little sunlight.
For most of spring until mid-autumn, green onion plants mostly stay a vibrant green. At such times, they generally get enough sunlight to create food for themselves through photosynthesis.
But what newbie home gardeners may fail to understand is that their leaf color is closely tied to the amount of light exposure they get.
If green onions are getting the ideal number of time under direct sunlight, they can make a lot of chlorophyll. This is the pigment that’s responsible for the lively green color of most plant foliage. Other than helping with plant color, it also aids with food production in plants.
So when they don’t receive enough light, the color of your green onions will become dull. Because they don’t receive much light, they can’t make their food and chlorophyll properly.
As a result, other color pigments such as carotenoids and anthocyanins become more visible in leaves. For green onion leaves, in particular, the carotenoid can cause them to turn yellow or pale orange with insufficient light.
Learn more about anthocyanins in our article on cacti turning red!
Make sure to place your green onions in an area that receives more or less 6 hours of direct sun exposure. When kept inside the house, you can place them near windows facing south or southwest.
If it gets too dark in your area during the colder months of the year, you can give them supplemental lighting as well. Place them 6–12 inches under a 15–20 W full-spectrum grow light (here on Amazon) for at least 12 hours.
5. High Humidity
High humidity can result in yellowing green onions as their leaves don’t tolerate damp conditions very well. Leaving scallions wet with very little airflow for over 6 hours also increases the likelihood of plant diseases.
Even though they are called bunching onions, live scallion plants shouldn’t be left to grow right on top of each other until they get overly crowded.
Having too many green onions growing in a very small space—even if they’re in raised beds or are grown directly in the ground. When they’re kept too close to one another, they won’t get enough air between them all.
At times, the lower portions of green onions may not even receive any ventilation at all—with all the leaves covering them up along with weeds that may be growing.
Low airflow coupled with high humidity within green onions will likely result in the development of various diseases. The chances of this happening increase substantially when their leaves are left wet for more than 6 hours at a time.
Regularly thin out your green onion plants to ensure that they don’t become overcrowded in their growing space. It’s best to plant them at least 6 inches from each other. Avoid growing them in areas that are shaded and where airflow is blocked.
When you give them enough growing space between each other, their leaves are less likely to become damp due to humidity. This way, you’ll also be able to control the spread of weeds which can choke them.
6. Nutrient Deficiency
Yellowing green onions leaves can result from a nutrient deficiency in their growing medium. The lack or absence of nitrogen and iron in soil often causes chlorosis.
Excessive soil moisture can also cause nutrients, mainly nitrogen, to start leaching. If you’ve only fertilized your green onion, then all of it would end up wasted.
Nitrogen is a key element for vegetative growth in plants. It also promotes green coloration in leaves. Deep green leaves indicate high nitrogen content in the soil, whereas pale green leaves indicate low nitrogen.
It also doesn’t help that plants in the Allium family, including scallions, are highly sensitive to nitrogen compared to other plants.
So when you notice that the leaves of the green onion you’re growing have started to turn yellow, it could be a sign that they can no longer find any nitrogen in their soil.
Besides nitrogen, not having enough iron and many other micronutrients such as zinc and manganese contribute to green onion leaf yellowing.
Pro Tip: Iron and sulfur deficiencies cause green onion leaves to turn yellow starting from young ones before spreading to older foliage. By contrast, most other nutrient deficiencies affect older leaves first.
Keep your green onion’s growing medium fertile with regular application of nutrient feeds. Whenever possible, get your soil tested first so you can correctly address nutrient deficiencies.
Check out our guide on the 13 methods for soil analysis!
If you can’t get your growing medium tested, then apply a mild balanced fertilizer to your green onions. Potted ones require less fertilizer, less often.
7. Pest Infestation
Irregular patterns of yellowing in green onions could be due to pest infestation. Harmful bugs eat, take shelter in, and lay their eggs in the plant causing stunted growth.
Most of the time, it’s pretty easy to tell when you have unwanted guests hiding in and feasting on green onions.
Common pests that affect green onions and cause yellowing leaves include:
- Bulb mites (Rhizoglyphus spp.)
- Leaf miners (Lyriomyza spp.)
- Leek moths (Acrolepiopsis assectella)
- Nematodes (Ditylenchus dipsaci, Meloidogyne hapla)
- Onion maggots and flies (Delia antiqua)
- Onion weevil (Ceutorhynchus suturalis)
- Thrips (Thrips tabaci, Frankliniella occidentalis)
Unlike yellowing due to undesirable growing conditions, yellowing leaf tissue in green onions that are caused by bugs appears uneven.
Oftentimes, these abnormal discolorations also appear with other unusual scarring and distorted leaves. Some nematodes, for instance, can also cause bloating.
It’s also important to note that these pesky insects not only damage the leaves of green onions. They can also wreak havoc on roots and bulbs. Pests can also carry diseases with them which could eventually kill the plant completely.
Always make time to check your green onion plants to see if unwanted bugs are living within the leaves. When you see any pests on them, spray them away using a high-pressure hose nozzle like the one below from Amazon. Then let the leaves dry properly.
Don’t wait until pests do serious damage before taking action. Otherwise, you may be left with no other choice but to uproot all your green onions and start again from scratch after treating your soil.
8. Plant Diseases
Unaddressed issues with growing conditions can result in green onions developing various diseases like fusarium basal rot that could lead to yellowing and plant death.
Though plants in the onion family are generally resistant to various infections, it isn’t completely invisible.
In damp cold environments with little to no airflow, they’re especially prone to developing a wide variety of fungal infections. Some of these, like downy mildew, can’t be easily resolved as there are no fungicides available to deal with them.
Here are some of the typical plant diseases that yellowing green onions may suffer from:
- Scallion rust
- Pink root disease
- Downy mildew
- Fusarium basal rot
- White rot
- Purple blotch
- Botrytis leaf blight
- Center rot
- Iris yellow spot virus
- Onion yellow dwarf virus
- Garlic mosaic
Now, if you’re wondering why a disease specifically named after garlic is included in the list, it’s because they come from the same family. Hence, they face similar issues and diseases.
Because plant diseases easily spread through unsanitized tools and contaminated soil and water. In other words, it’s best to practice proper hygiene as much as possible—as ridiculous and impossible as it sounds.
Seriously infected green onions are rarely salvageable. In such cases, they can only be discarded to prevent the further spread of plant diseases. After the area they were planted in has been treated, look for another place to keep them.
Better yet, grow your green onions in planters for easier control and better management. If they do get infected, the problem will stay contained in a small area.
Can you eat a yellowing green onion?
You can still eat yellowing green onions if they only started getting discolored in storage days after harvest. However, they have little to no flavor compared to crisp green freshly-cut spring onions. If the yellowing is due to pests, diseases, or any other reason you’re unsure of, don’t eat discolored spring onions.
Is it possible to make yellow spring onions green again?
Parts of green onion leaves that have turned yellow will no longer regain their original vibrant color, regardless of the reason behind the discoloration. Further yellowing of spring onions, however, can be prevented by correcting undesirable growing conditions like providing sufficient water and sunlight.
Summary of Why Green Onions Turn Yellow
Even healthy green onions can develop old yellowing leaves as a natural consequence of aging. For bulbing species, this is commonly a sign that it’s time for harvesting. But for bunching onions, this can signal that flowers will form and bloom soon.
All other causes of yellowing green onions generally involve improper watering, low temperatures, insufficient light, high humidity, nutrient deficiencies, pest infestation, and plant diseases. Such problems must be resolved as soon as possible to save scallions and prevent irreversible plant death.
- “Bulb onion production in Hawaii” by the e College of Tropical Agriculture and Human Resources in University of Hawai’i at Manoa
- “Home Vegetable Gardening in New Mexico” by Stephanie Walker in New Mexico State University
- “Yellow Leaves Can Indicate Plant Problems” by Erin Knowles in Illinois Extension
- “Why do leaves change color in the fall season?” by Richard K. Simpson in Arizona State University
- “Identifying Pests of Onion and Garlic and Their Damage” by n/a in University of California Agriculture and Natural Resources