Garden geraniums (Pelargonium spp.) are well-known for their bright colours and easy-to-grow nature. While most people associate these flowers with annual beds and outdoor containers, many types of geranium also flourish as houseplants too.
An indoor geranium can bloom almost year-round with adequate light. With that said, geranium foliage is nearly as interesting as the plants’ flowers. In this article, I’ll cover the most common reasons for geranium leaves turning yellow and the best steps you can take to fix it.
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Why Do Geranium Leaves Turn Yellow
The name ‘geranium’ can refer to several different plants. Species that make great houseplants (and that I’ll be focusing on in this article) include the:
- Zonal or common geranium (Pelargonium x hortorum)
- Ivy-leafed geranium (Pelargonium peltatum)
- Martha Washington geranium (Pelargonium x domesticum)
In the majority of climates, these geraniums will only survive for a single season outdoors. As houseplants, however, they can live for several years with proper care. I’ve personally encountered a potted geranium that was over 40 years old!
Yellow leaves can be an inevitable part of the ageing process for geraniums that are a year or older. Geraniums develop woody stalks and drop their lower leaves as they grow. In this specific circumstance, yellowing foliage is nothing to worry about.
More often than not, yellowing leaves on a potted geranium are a clear sign that something is wrong with the plant’s health or surrounding environment.
Plant foliage appears yellow because it lacks sufficient chlorophyll — a condition called chlorosis. Nutrient deficiencies and disease are often to blame for this symptom. But chlorosis in geraniums can also be caused by cultural factors like improper watering, cool temperatures, or too little sun exposure.
Over or Under Watering
Overwatering is by far the most common cause of yellow leaves on just about any common houseplant. Signs of overwatered geraniums include yellow leaves often accompanied by drooping flower stalks. Underwatered geraniums typically present with yellow leaf margins that have a dry texture. These are just general guidelines, however, and the only guaranteed way to tell the difference is to examine the soil’s moisture level.
Potted geraniums are very easy to overwater. Unfortunately, the yellowing caused by overwatering is often mistaken for too little water. This, of course, only exacerbates the issue.
Geraniums are drought-tolerant flowers that prefer to have their soil dry out between waterings. Depending on the size of your geranium pot, you can let the soil dry out up to 6 inches deep before watering.
Potted geraniums should only be planted in containers with plenty of drainage holes. They also require well-draining soil. Avoid placing your indoor geraniums in saucers that can collect standing water.
If you believe your geranium is suffering from too much moisture, place the plant in a bright, warm location where it can dry out as quickly as possible. Withhold additional water until the geranium shows signs of recovery. I also recommend double-checking that your geranium container is draining properly.
If your geranium is showing symptoms of dehydration, I suggest re-evaluating your watering schedule as well as your household humidity. Add some organic material to the potting soil to improve moisture retention without interfering with good drainage.
Low Temperatures
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Geraniums prefer daytime temperatures between 65 and 70°F and nighttime temperatures above 55°F.
Potted geraniums kept somewhere like an unheated covered porch may develop yellow leaves, among other symptoms. Similar issues can arise if you place your geranium too close to a drafty window or even near a household AC vent.
If you typically keep your geraniums outdoors during the summer, you’ll want to relocate them indoors in early fall at the latest. In the spring, do not move potted geraniums outdoors until nighttime temperatures are consistently above 50°F.
Insufficient Sunlight
The one thing about geraniums that can be a problem when growing them as houseplants is their need for direct sunlight. Indoor geraniums need 6 to 8 hours of bright sunlight per day to remain healthy and produce near-constant flowers.
Too little sunlight can turn geranium leaves pale green or yellow. This happens because the plant senses the lack of light and stops producing high amounts of chlorophyll to conserve energy.
For the best results, place potted geraniums near a bright window that receives direct sunlight throughout the entire day. If you live in the Northern Hemisphere, an east- or south-facing window is ideal (vice-versa for those of you living in the Southern Hemisphere).
Providing our houseplants with several hours of daily light isn’t always possible. In such cases, you can set up a grow light above your geraniums to make ends meet. Since grow lights are considerably weaker than the natural sun, I recommend scheduling the light to stay on for up to 14 hours per day.
Nutrient Deficiencies
Geraniums rarely display nutrient deficiencies when grown as annuals. (To put it bluntly, annual flowers typically die off before any deficiencies have a chance to cause visible symptoms.) But this isn’t necessarily true of those kept as houseplants.
The nutrient neglect most likely to cause chlorosis in potted geraniums is nitrogen and potassium. Nitrogen and potassium are primary macronutrients, meaning that plants consume them in very large quantities in comparison to other nutrients. Lesser nutrients may cause yellow leaves to include iron, zinc, manganese, and sulfur.
When nutritional imbalances are to blame, yellowing may appear on the margins of geranium leaves first. A nitrogen deficiency can also present as purple discolouration along leaf veins.
A balanced feeding regimen is the best way to stave off nutritional deficiencies in geraniums. I recommend using a slow-release fertilizer designed for houseplants or a comparable liquid formula diluted to half its normal strength.
Depending on your chosen fertilizer, geraniums tend to perform best when fed once or twice per month during the growing season. Cut back on or withhold fertilizer during the winter as growth naturally slows.
Pests and Disease
While there aren’t any unique pests that target indoor geraniums, you need to keep an eye out for all of the usual offenders when growing these flowers as houseplants. As far as yellow foliage is concerned, aphids and spider mites are usually to blame.
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Pests like aphids and spider mites feed by piercing and sucking liquid out of plant leaves. One of the clearest signs that one of these pests is at work is the appearance of countless yellow spots on your geranium leaves. These spots are where the pests have sucked chlorophyll out of the leaf tissue.
You can control both of these pests with horticultural oil or insecticidal soap. Mild infestations can also be removed by spraying your geranium’s foliage with clean water. I recommend quarantining infested plants to prevent the spread of aphids or spider mites to other pots.
Disease
Geraniums are susceptible to a few diseases that can cause yellow leaves:
Bacterial Blight
Blight (Xanthomonas campestris pv. pelargonii) is a common problem and sadly geraniums are particularly susceptible to it. Identifiable by way of the small watermarked indentation of up to 1/4 inch and spread to kill the leaf. The disease is carried in soil and on surfaces making it important to dispose of infected plants.
Verticillium Wilt
According to Utah State University, verticillium wilt (Verticillium albo-atrum) causes leaf yellowing and drying starting from the base of the plant. Most cases of verticillium wilt — particularly in houseplants — result from using infected soil.
Southern Bacterial Wilt
Southern bacterial wilt (Ralstonia solanacearum) causes geraniums’ lowest leaves to wilt, turn yellow, and prematurely drop. This bacteria is frequently transmitted when in-ground plants are relocated indoors.
Your geranium may have been exposed to these diseases in its original greenhouse or plant nursery. It’s also possible to introduce diseases via contaminated soil or new houseplants.
FAQ Yellow Leaves on Geraniums
Final Thoughts on Geranium Leaves Turning Yellow
The sheer number of reasons your geranium might be turning yellow can be overwhelming. However, it’s important to keep in mind that most potential causes ultimately come down to proper care.
I recommend re-evaluating the current maintenance routine any time a houseplant develops yellow leaves. Something as simple as a too-dark location or overzealous watering could be to blame for your geranium’s discolouration.
If nothing in the environment seems to be responsible, you can then move on to potential issues like poor nutrition or an infectious disease.
Remember: No matter the root cause of your geranium’s yellow foliage, prompt diagnosis and treatment are the biggest contributors to a successful recovery.
Citation
Utah State University – Verticillium Wilt
Penn State Extension – Bacterial Blight of Geranium
Source: https://t-tees.com
Category: WHY
