Geraniums are small, beautiful, perennial flowers that are low maintenance, quick spreading, and come in a variety of bright colors. Many geranium varieties are drought tolerant, hardy, and will last for years in the right locations.
But when they start to show signs of trouble, they head downhill fast. There are several symptoms that every geranium gardener should look out for, including the yellowing of leaves.
This article describes the plaguing issues surrounding geraniums, including why the leaves on your geranium are turning yellow and what to do about it.
Why Do My Geraniums Have Yellow Leaves?
The yellowing of leaves is called chlorosis. This term describes the phenomenon that occurs when environmental factors cause the leaves of plants to produce insufficient amounts of chlorophyll. This leads to otherwise lush, green foliage losing its vibrancy.
The most common environmental factors that can cause geranium leaves to turn yellow include inadequate watering, lack of sunlight, low temperatures, nutrient deficiencies, pests, and diseases.
While sometimes subtle, chlorosis is usually a first indication that there is a problem with your plants, so it should be looked for when monitoring the overall health of your garden.
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Over or Under Watering Geraniums
Geranium plants will often have a hard time recovering from constant under or over-watering, so keeping a consistent eye on the moisture level of the soil is pivotal in maintaining a healthy geranium plant for years to come.
While they will most likely need weekly waterings, geraniums are best left off a strict watering schedule. By this, I mean check the soil instead.
If the first 2 inches of the soil is dry, then the plant needs water. If there is moisture just below the surface of the soil, then the geranium plants can be left a few days before another watering.
I find this technique is especially helpful when working with gardens exposed to the elements.
Overwatering can quickly cause the soil to become saturated, depleting the plant of vital oxygen. Geraniums are very susceptible to those flooded conditions and will quickly wilt and turn yellow.
If the saturated conditions are left to continue, then the plant will die.
In addition, overwatering increases the chance of fungal development later in the season and leaches the nutrients in the soil.
Geraniums are hardy and relatively drought-tolerant. But if they don’t receive any water they will begin to wilt and experience severe leaf chlorosis.
To fix this, I suggest consistently adding a small amount of water to your geraniums until they stand upright again. This ensures you don’t drown the roots or leach the nutrients from the soil.
Lack of Sunlight
It is crucial that geraniums receive at least 6 hours of direct sunlight a day or they will begin to show signs of discolored – yellow – foliage, as well as stunted growth, and a lack of flower production.
This can be fixed by transplanting the geraniums to a more suitable location or placing them in a south-facing sunny window when growing indoors.
Low temperatures can also cause your geranium plant leaves to turn yellow. This is usually a result of a lack of sunlight or low air temperatures.
The low air temperatures in the fall will trigger the plants to ‘senesce’, in which the yellowing of leaves is the beginning process. Any amount of frost will cause your geraniums to die back, but these perennial plants should return the next spring.
Like all plants, geraniums need several different macro- and micronutrients that are naturally found in the soil. When these nutrients are in short supply or are unavailable due to issues like soil pH imbalances, then nutrient deficiencies can occur.
A lack of nutrients such as nitrogen, potassium, magnesium, and iron will inhibit your geraniums from completing their metabolic activities related to growth and reproduction. This causes major issues such as stunted growth, poor flower production, severe chlorosis of foliage, and death.
Signs of nitrogen deficiencies in geranium plants include the rapid yellowing of leaves starting in older leaves and advancing to younger leaves as the deficiency increases.
A lack of nitrogen is often caused by the absence of organic matter in the soil, insufficient fertilizing, and nutrient leaching from heavy watering.
These deficiencies can easily be prevented by starting with a rich sandy loam soil mixture.
Nitrogen is in greatest demand during the reproduction phase of a geranium’s growth cycle, so add a nitrogen-rich bloom fertilizer when flowering begins.
Potassium deficiencies will begin as yellowing leaf edges and veins and lead to the curling and greying of the entire leaf.
Symptoms will start in the older leaves and quickly progress to younger leaves as it worsens.
Chlorosis from potassium deficiencies will typically present by mid-summer. This particular nutrient becomes less bioavailable during times of drought so signs of potassium deficiencies are likely to occur after geraniums have been severely under-watered.
Magnesium is involved with the production of enzymes, cell membranes, and leaf tissue, so when deficiencies occur signs of foliage discoloration, overall stunted growth, and poor leaf production are quickly evident.
Magnesium deficiencies will begin as yellow interveinal striping in the newest leaves and progress to develop yellowish-brown spots and reddish-purple tips on its leaves and stems.
Iron deficiency symptoms are distinct and cause the entire leaf to yellow while the veins remain green.
While iron is often present in the soil, it can be unavailable to the plant due to environmental conditions such as over-oxygenation of the soil, pH imbalances, or chemical binding to other materials.
As an essential nutrient, an iron deficiency will cause the geranium plant to stop growing, and will quickly progress to leaf chlorosis, and eventually death.
Sulfur deficiencies in geraniums will present symptoms of interveinal yellowing with overall chlorosis starting out more pronounced in the younger leaves of the plant and spreading as the deficiency worsens.
Calcium deficiency symptoms begin as slight chlorosis and progress to noticeably stunted growth.
In times of drought or underwatering, calcium becomes less bioavailable. I recommend adding an organic calcium source such as crushed eggshells to the topsoil of your geraniums during those times.
The nutrient zinc is one of the most common deficiencies found in flowering plants. Zinc is necessary for the production of chloroplasts which is why the lack of zinc will cause interveinal yellowing leaves.
As a zinc deficiency is allowed to progress and worsen in geranium plants, the entire leaf color gets lighter and lighter, progressing from green, then yellow and eventually bleaches and becomes predominantly white.
If nutrient concentrations are at high levels in the soil, then nutrient toxicity can occur and chlorosis is the most common indicator of this.
Over-fertilization and misuse of products are the most common causes, while soil pH issues can also be a culprit. For this reason, I recommend that you always fertilize the soil, never the foliage. Unfortunately, if fertilizer burn encompasses the entire plant, then it’s not likely to survive.
Salt toxicity symptoms can present as a lack of potassium, but when severe yellowing of leaves occurs, this is most likely a result of excessive amounts of sodium in the soil typically caused by over-fertilization.
The good news is that geraniums are more tolerant than most plants of salt and can easily survive normal amounts of excess salt by flushing the soil with fresh water.
Common geranium varieties are cultivated from native species that don’t require fertilizer to survive, which is why geraniums can be sensitive to the effects of over-fertilization.
So, assuming the base soil is rich in organic matter, most cultivated geranium varieties will benefit from holding out on fertilizing during the growing season.
Waiting to fertilize until the geranium flower buds have developed will ensure your geraniums are given nitrogen when needed while limiting the chances of over-fertilizing.
Following bud production, use an evenly balanced, diluted liquid fertilizer – applied directly to the soil – on a weekly basis to maintain growth throughout the rest of the growing season. It’s worth noting here that applying liquid fertilizer to the leaves can cause fertilizer burn, which can lead to permanent chlorosis.
Alternatives to fertilizer
An alternative option to liquid fertilizers is to plant your geraniums in fortified soil. This will provide your geraniums with the necessary nutrients it needs to survive that growing season.
If your geraniums are planted in a perennial garden that does not receive new soil each year, then you will need to add an amended topsoil over the next few seasons. This is essential if you want your geraniums to continue producing plentiful blooms.
Pests & Diseases
Geranium species are host to many pests and diseases, including spider mites, aphids, viruses, and fungi.
According to Oregon State University, these diseases and pests are best controlled by adequate spacing, and proper airflow, as well as by implementing Integrated Pest Management (IPM) techniques.
IPM is a scientifically proven way of combating these unwanted pests and diseases without using excessive insecticides. Some of the techniques implemented in IPM include the removal of invasive plant species that lure pests, the planting of native species that deter pests, and the creation of shelter that attracts predatory insects, birds, and animals.
Spider mites are tiny insects that do enormous damage if left untreated. Spider mites will leave small yellow dots all over the surface of the leaves, and as the infestation worsens the entire plant will begin to wilt.
These particular pests produce webbing that is evidently present on the undersides of every infected leaf.
Spider mites are common and naturally plentiful in the environment, but an infestation can be easily prevented by spraying the leaves with mite-specific insecticidal soap, or an all-natural mixture that includes essential oils such as lemongrass and neem.
Aphids and Leafhoppers
Aphids, beetles, and borers are all attracted to geranium plants. Plants that are exposed to this type of infestation will show signs of physical leaf damage along with the presence of yellowing or browning leaves.
Even more destructively, these piercing and sucking insects can deposit bacteria, fungal spores, and viruses on the plant during their visit, which can cause major infestations to spread rapidly.
Removing the infected plants using insecticides is necessary to control the spread.
FAQ Yellow Leaves on Geraniums
Why are the leaves on my potted geranium turning yellow?
Besides the most common causes of yellowing leaves that have already been discussed, potted geranium may be suffering from root issues. If the roots have started to bind because of a lack of space in its container, then its leaves might start to yellow regardless of whether it has adequate growing conditions.
Should I cut off yellow geranium leaves?
Yes, you should remove yellowing leaves because it can prevent more pests from being attracted to the garden area. If the yellowing is caused by a fungus, then removing leaves is important in preventing further spread. Remove less than 1/3 of the geranium’s leaves will prevent additional stress.
Why are the lower leaves of my geranium turning yellow?
Overwatering is a common cause of lower leaves turning yellow. If the soil is soaked, then that is probably the culprit. Otherwise, it could also be from a fungal infection spread by contact with the soil.
Verdict: Why Are the Leaves on My Geranium Turning Yellow
The most common environmental factors that can cause geranium leaves to turn yellow include inadequate watering, lack of sunlight, low temperatures, nutrient deficiencies, pests, and disease.
To identify the exact cause, it is key that you consider each of these factors in turn. Only then will you be able to unravel what is causing the leaves of your geranium to turn yellow. Remember:
Geranium plants have a hard time recovering from constant under or over-watering and low temperatures, which can both be to blame if your geranium suddenly has yellow leaves.
Make sure your geraniums are receiving at least 6 hours of direct sunlight per day. If not, they will begin to show signs of foliage discoloration, as well as stunted growth and a lack of flower production.
Finally, nutrient deficiencies can also be responsible for why the leaves on your geraniums are turning yellow and are related to either the absence of organic matter in the soil, insufficient fertilizing, or nutrients leaching from heavy watering.