Similar to how sailors can predict the weather by the color of the sky, (“Red sky at night, Sailor’s delight. Red sky in the morning, Sailors take warning”) gardeners get clues on what’s up with their plants by the color of their leaves.
Red leaves on geraniums are a warning to gardeners that the plant is stressed.
As pretty as it is to have unexpected colors bounce into your garden, red leaves on geraniums aren’t a good thing.
Stress causes discoloration. Unfortunately, there’s a list of things that can stress geranium plants easily.
As you’ll discover in the information detailed below, there are several stress factors that contribute to leaf discoloration. All of them can be fixed easily.
Table of Contents
Why do geranium leaves turn red?
Geranium leaves turn red mostly in spring or fall. It’s usually a combination of falling temperatures (50 degrees Fahrenheit or 10 Celsius) and a phosphorous deficiency. Other factors include soil pH dropping below 5.8, transplant shock, inadequate watering, or a nitrogen deficiency.
Causes of Red Leaves on Geraniums
Red leaves on geraniums in spring or in the fall are usually caused by temperatures being chillier than the plant expected.
Geraniums begin to struggle when the temperatures start dropping below the 50 degrees Fahrenheit mark (10 degrees Celsius). They can cope with the odd drop in temperature but a sudden plunge will stress it, regardless of how healthy it appears.
During springtime, wait until after the date of the last frost before acclimating your plant to outdoors.
It shouldn’t take up permanent residence in a garden until early April in most zones.
In the fall, daylight hours get shorter. That’s when you need to prune geraniums back to overwinter them indoors before the cold snap hits.
- Red leaves in the fall are when to get your plant indoors for overwintering.
- Red leaves in the spring will fix themselves when the temperatures pick up.
That is unless you haven’t trained it to expect the lower temperatures…
This is mostly a problem for geraniums grown from seed or from rooting geranium plants indoors where it’s warmer, and then transplanting too early.
It can also be due to failing to acclimate the plant before transplanting it into the ground soil.
Indoors, most plants have bright light and warmth with relatively stable overnight temperatures too.
Being put outside without acclimation first will be a shock to the plant.
Shock causes stress, and geraniums make their stress levels known with blushing red leaves.
Provided the roots are well-nourished, and conditions for growing geraniums are optimal, they will come around when they get used to the new conditions.
Bone dry roots will cause red leaves on geraniums. If you’re convinced all other conditions are primed for your geranium to be growing healthy, there’s likely a problem at the root level.
This is evident when you start seeing brown to black stems and brown leaves falling off the plant.
Root drought though can be a sign of severely dry roots which can only show as red leaves early on.
Give the plant a thorough watering at soil level and it’ll pick up fast. If it’s just a drink it’s been crying out for.
It might need some food.
When geraniums lack phosphorous, the veins take a reddish-brown shade. If you’re seeing green leaves with red veins, it’s likely your geranium’s lacking phosphorous
Without this, flowering is affected and growth gets stunted.
If left unchecked, red spots start appearing between the veins, turning brown, then black, then they die and fall off.
By the time you notice the veins on leaves reddening, it’s already been deficient for at least a month.
The other core nutrient outdoor geraniums need is nitrogen.
On most other plants, a nitrogen deficiency is often identified when there are yellowing leaves.
Because of the pigmentation differences on geranium leaves, when nitrogen levels are too low, the leaves on some cultivars turn red.
A cause of nitrogen deficiency is leaching from ground soil when there’s been heavy rainfall.
That’s not to say if you’re unlucky enough to experience a few days of heavy rain to go apply more fertilizer.
When you apply fertilizer to the soil, it takes time to convert nitrates to soluble nitrogen that the plant can consume.
One trick to speed up nitrogen uptake in pre-fertilized garden plants is to raise the ambient temperatures.
For each 10-degree Fahrenheit temperature rise, the speed of nitrate conversion doubles.
A thin layer of mulch over the topsoil speeds the process along.
It’s better to encourage existing fertilizers to convert the energy stored, than it is to risk over-fertilizing your plants, which can stress it just the same, causing the same red leaf issue.
Soil pH Imbalance
Soil acidity needs to be between 5.8 and 6.3 for geraniums.
Around 5.8 for zonal geraniums and above 6.0 for regal geraniums, ivy geraniums, and other geranium varieties.
The soil acidity is imperative because under 5.8, in most cases, will be too toxic. In geraniums, the most toxic nutrients are manganese and iron.
It is rare, but it is worth doing a soil pH test to make sure because as mentioned, anything stressing a geranium causes the leaves to turn red.
If you catch pH toxicity at the stress stage and correct it, the plant can get back to growing healthy.
If you don’t identify a pH imbalance early, the result will be brown spots on leaves, yellow edges, and stunted growth.
A far cry from what can look like pretty red leaves that add color to your garden unexpectedly.
As pretty as red leaves are in the fall (or any time of the year for that matter) they aren’t a color you want to keep on the leaves of your geraniums.
Red blooms, yes. Red leaves, no!
Frequently Asked Questions Related to Red Leaves on Geraniums
Should all the red leaves on geraniums be removed?
Red leaves still provide some energy to the plant. Pinching them all off suddenly stresses the plant more. Gradually pinch off a few red leaves daily in early spring and it will fill out as the night temperatures begin to warm up. Regular pinching encourages bushier growth anyway.
Are the stems with red leaves healthy enough to use the cuttings?
Provided the red leaves are on the lower part of the stem, it’s only a sign of stress. The top few leaves should be green for growing new plants from cuttings. So long as the stem is green with no signs of browning, it should root successfully in soil or water.
Daniel has been a plant enthusiast for over 20 years. He owns hundreds of houseplants and prepares for the chili growing seasons yearly with great anticipation. His favorite plants are plant species in the Araceae family, such as Monstera, Philodendron, and Anthurium. He also loves gardening and is growing hot peppers, tomatoes, and many more vegetables.