8 Reasons Your Geranium Leaves Are Turning Yellow, and What to Do About It

Geraniums are a staple in our summer containers and flower beds for good reason. They’re available in a range of flower colors and combinations and sport attractive green foliage. But if your geranium leaves are turning yellow, it can be alarming. However, most causes of yellowing geranium leaves are easily corrected. Here’s how to figure out what’s going on with your plant and how to fix it.

1. Overwatering

This might be the most common cause of yellow geranium leaves. While some container and bedding plants like moist soils, geraniums prefer drier conditions. They are drought-tolerant and do poorly in continuously wet soil. Yellow leaves at the bottom of the plant are a sign of overwatering or poor drainage. 

Check the drainage holes; some decorative pots don’t have any or only one small hole. Decrease the watering frequency and check the soil moisture with your finger before watering. When the soil feels dry 1 inch below the surface, it’s time to water.

2. Underwatering

Many plants show yellowing leaves when they lack water. While it isn’t common for geraniums, since they don’t mind being dry, they eventually become drought-stressed and develop yellow leaf edges and tips. 

If the soil feels overly dry or a potted geranium feels extremely light for its size, give it a slow, deep watering. Continue adding water even after it flows out through the drainage holes, as older dry potting mix does not absorb water well. You may need to water it once and a second time, half an hour later.

Give geraniums in garden soil a thorough, slow watering with a watering can or a rain wand on a hose. Water until the soil feels moist as deep as your finger reaches.

3. Nutrient Problems

Lack of proper nutrients causes yellowing leaves in many plants, and geraniums are no exception. Unless there is another reason for yellowing leaves, the cause is often nitrogen deficiency. While low iron, magnesium, or other trace nutrients may also cause yellowing, nitrogen is a primary nutrient and is the most likely culprit. 

Apply a balanced, general-purpose flower fertilizer following the package directions. The plant should start to green up or at least stop yellowing within a week or two. Don’t succumb to the urge to overfertilize, which leads to other problems. 

4. Bacterial Leaf Blight

A bacterium that only attacks geraniums, Xanthomonas campestris pv. pelargonii, causes brown blotches with yellowing borders on geranium leaves. Symptoms begin as small water spots and then develop into brown leaf areas, often surrounded by yellowing V-shaped borders. Once plants are infected, there is no cure.

The bacteria are spread by unsanitized tools, splashing water, or infected potting mix (that’s why reusing last year’s potting mix unsterilized is not recommended). The bacteria survive on plant debris in the soil over winter, so good garden hygiene is important around geraniums. Verticillium wilt causes similar blotches and yellowing. 

Since the bacteria spread and overwinter in the soil, if you notice this pattern, it’s time to either rip the plant out and dispose of it or, for potted plants, quarantine the plant. Your best line of defense is proper watering, fertilizing, and sufficient sunlight.

5. Natural Aging

Geraniums, like many plants, will sometimes drop underperforming leaves as they get older. Those at the bottom of the plant, likely shaded by the upper foliage, are often candidates for the plant to self-prune. The plant moves nutrients from the lower leaves to the upper leaves, causing the old leaves to yellow and eventually drop off. It’s natural and nothing to worry about.

6. Sunlight

Geraniums need sunlight, and if planted in a fully shady spot, they usually grow slowly, flower poorly, and may even turn slightly yellow. For potted geraniums, move the planter to an area with at least partial sunshine. For those planted in the ground, you may be able to trim back the leaves of a nearby plant that is shading it out or transplant them.

Too much sunlight, normally only a problem in areas with extremely hot climates, may cause plants to bleach out and look pale, which may be mistaken for yellowing. If you live in areas where the sun can fry an egg on the pavement, plant geraniums where they’ll get morning sun but afternoon shade. 

7. Cold Snaps

Yellow leaves are a sign of stress, and a sudden cold snap may cause yellow leaves on your geraniums. For potted geraniums, consider bringing them indoors if an unseasonable chilly night is forecasted. If you’ve already planted your geraniums in the ground, cover them with a sheet or let them tough it out; they often respond with new green growth in a few days.

8. Herbicide Damage

Yellowing leaves can also occur as collateral damage from nearby weed killer applications. Broadleaf herbicides that you or your neighbors use on patios and sidewalks to kill weeds growing in the cracks may drift onto your geraniums. Even DIY weed killers made with common household chemicals or a flame weeder used on a nearby gravel path causes leaves to yellow. In the worst case, herbicides kill desirable plants.

Limit the use of weed killers, whether commercial or DIY, near your garden beds, and be aware of the prevailing wind direction when planting if you know a neighbor uses these products.