Besides their beautifully large, vibrant colored blooms, sunflowers are also known for their use in cooking oil, meal, and confectionary products. Growing and cultivating these flowers can come with its challenges, though. Even on a smaller scale, growers can run into various issues.
The most common problem to occur to sunflowers is when their leaves turn yellow. Do you want to know why are your sunflower leaves turning yellow?
Well, when a plant’s characteristics change, they are usually under some kind of stress. In the case of yellowing leaves, the root problem is generally either from nutrient deficiencies, overwatering, or attacks from pests or diseases.
In this article, we’ll go through all the reasons why sunflower leaves can start turning yellow in extensive detail. We’ll also look at some really handy prevention methods and solutions to remedy the problem if it occurs. Let’s go!
Table of Contents
Sunflower Leaves Turning Yellow: Reasons and Solutions
When we think of sunflowers, we picture fields full of huge, yellow, and brown colored heads. You may even be lucky enough to spot the non-generic creamy golds, oranges, deep reds, and chocolate brown colors.
Whatever the type, most fond memories of road trips during summer generally leave us with a deep connection to these striking flowers. Sadly though, we only really see the good side of them, where they are grown seamlessly and to perfection.
In reality, though, many growers face a range of problems; one of the most common is when the sunflower leaves start turning yellow. Let’s look at the different reasons why this could occur.
Nutrient Deficiencies
Sunflowers are the type of plant that needs quite a bit of food. Given that they grow quite tall, supplying them with sufficient nutrients will allow them to reach their full potential.
The plant food essentially allows them to build a strong, stable stalk and encourage a deeply entrenched root system.
This helps anchor the plants to stop their heavy heads from swaying with excessive weight. Most gardens and growing fields these days just don’t have the amount and quality of nutrients needed for well-rounded crops to be produced.
When yellow leaves are present, looking at their characteristics of them will help to understand exactly which nutrient is lacking.
For example: When the discolored leaves are still slightly green near the vein lines, this tells us that the plant is lacking nitrogen. When the yellowing leaves have a purple or reddish tinge, they tell us that more phosphorus is required. This can be adjusted by feeding them a fertilizer with slightly more of these 2 components.
Nitrogen is responsible for ensuring that energy is available when and where the plant needs it. It is a component of chlorophyll. Chlorophyll helps plants take in sunlight energy to allow photosynthesis to occur (energy conversion).
Phosphorus helps the plant to grow, maintain and repair its tissue cells. It also helps the plant to balance the use of other important vitamins and minerals.
These imbalances can be corrected by using a well rounded 10-10-10 NPK mix. Research has proven that granulated blends work best as they release the nutrients slowly, beginning in spring and lasting through the blooming summer season.
Water Stress
Another reason for a sunflower’s leaves to turn yellow is by overwatering. Furthermore, this condition can be amplified if there is inadequate drainage. The water intake of a sunflower can be a bit tricky. On the one hand, they have a deep root system, so they need quite a bit of water.
However, on the other hand, watering them too much and too often will drown the roots and cause them to rot. As a result, the leaves will turn yellow due to stress.
Initially, the leaves will start to droop and become weak as the rotting sets in. As it works its way up through the plant, the leaves will slowly fade from their vibrant greens to more of a bland yellow color.
The best way to correct this issue is by first putting a hold on any watering until the soil has had the chance to completely dry out. Then a little bit of trial and error is needed. Give the sunflower a little sprinkle and wait a few days to see if the leaves slowly fade back into greens.
If not, it is a good idea to remove the plant from its soil and repot it with a better draining mix or add some compost to the ground to help aerate it a bit better. They thrive best in neutral to slightly alkaline soil where the pH is between 6.0 and 7.5.
Once you have replanted the sunflower, go a bit lighter on the watering until you are sure the problem has been corrected. Check the soil condition regularly by sticking your finger around 2-3 inches into it and seeing if there is any remaining moisture. Suppose it comes up dry, then water sparingly.
Pests
The biggest problem with water stress issues is the insects and bugs that feed on the plant in this weakened state. When these small armies are present, the leaves can turn yellow via the stress from damage caused by feeding.
Surprisingly, sunflowers are pretty resilient when it comes to insects and bugs. The ones that do cause some damage include:
Sunflower Beetles
Sunflower beetles aren’t a problem as they feed on the leaves. This is not a big deal for mature plants but can create problems for younger plants that have their first true leaves destroyed.
Cutworms
Cutworms are a little similar to beetles in that they only really affect the leaves of younger plants. They tend to leave notches or holes as they go on a feeding frenzy. Once they latch on, they can cause wilting from the stress, which turns the leaves yellow.
Sunflower Borers
Sunflower borers and stem maggots can cause some real damage to plants. They do exactly as the name suggests. They bore into the stems of the sunflower plants, which supply them with an abundant source of food.
As a result, the whole structure of the plant becomes weak, and the vegetation can easily die off. They can move from stem to stem with relative ease and take down large areas of the crop quickly.
Sunflower Moths
Sunflower moths have a real talent for destroying sunflowers. They lay their eggs inside the flower heads. Once the armies of the eggs hatch, all of the larvae feast on the flower heads. As a result, the heads become mutilated, leaving very little to survive.
Grasshoppers
Grasshoppers and certain caterpillar types enjoy snacking on the leaves of the sunflowers. They don’t cause too many problems when only a handful is present. However, larger groups can do some real damage as they work their way from plant to plant.
How do you get rid of them?
We always recommend using organic insecticides such as neem oil to help keep pests like these away. Alternatively, keep your growing areas free of weeds and other debris to minimize the risk of inviting unwanted guests. They love fodder plants, so removing them will give your sunflowers a better chance of surviving and thriving.
Diseases
Most fungal diseases cause yellowing of the leaves as the plant stresses when it begins to rot. Some other diseases that make the leaves go yellow include:
Chlorosis
Chlorosis is a condition that occurs when the plant doesn’t have enough chlorophyll. Chlorophyll essentially absorbs sunlight to assist in the process of photosynthesis.
When the sunflowers aren’t receiving enough sunlight, they cannot convert the energy and therefore create more chlorophyll due to the overall process.
Leaf Spot Disease
Leaf spot diseases are caused by poor circulation, which can be amplified by poorly spaced planting and high humidities. It can also be compounded by overwatering.
The stress of this disease makes the leaves fade into a yellow color, as well as the common black spotting. Unfortunately, when any plant suffers from leaf spot disease, the affected leaves will die and drop. They will not turn green again.
Root Rot/Fungal Rot
Root rot or fungal rot is usually a result of overwatering. The roots lay in stagnant water surrounding them and eventually rot out. Once this disease establishes itself, it is quite difficult to treat. The stress of the illness makes the leaves turn yellow, starting from the lower regions of the sunflower and working its way up.
How do you get rid of them?
These types of diseases are a bit tricky to manage. If they go unnoticed and are allowed to establish themselves, it’s best to pull the plants up and check the conditions of the root system. They will most likely die if the roots are mushy and brown or black.
If there’s still some life in 30-50%% of the roots, prune away the decaying matter and discard them carefully as the mold can spread. Once you have a clean root system, use a copper based fungicide to treat the affected areas and report or plant accordingly.
Other Factors
Some other reasons that the leaves of sunflowers may turn yellow include general stressors such as::
- Transplant shock – This temporary condition can turn the leaves yellow or brown when the plant settles into its new location. Avoid doing so in extreme heat as it will dry them out and make them extremely brittle.
- Cold temperatures – Sunflowers can grow just fine down to around 25°F (-4°C) but any lower will make their leaves turn palish yellow. They will also slow down their production and growth rate when it gets too cold.
- Lack of sufficient light – All plants need light to produce the energy needed to grow efficiently. When there isn’t enough, the leaves turn yellow as they stress and focus energy on growing more important areas of the plant.
Symptoms of sunflower leaves turning yellow
Sometimes the root cause of yellowing leaves has gone too far and makes the sunflower unsavable. Therefore, if you read the warning signs early on, your sunflowers will have a much better chance of survival.
Let’s look at the symptoms to look out for to give them a fighting chance.
Discoloration
The first and most obvious thing you will notice is the leaves fading in color. As the stressors take hold of them, they will focus their energy on keeping the most important parts alive and functioning.
You will notice that the regions closest to the roots and the stem stay truer in color. The lower leaves will start to fade first, and the discoloration will slowly work its way up through to the tip of the plant.
Stunted Growth
Once the leaves lose their beautiful vibrant green color, the whole plant will go into energy conservation mode and stop trying to push up any higher. This will leave the plant to slow right down in the growth or even stop as it tries to stay alive.
Brown or black spots on the leaves
Once the leaves begin to spot (it’s not always guaranteed to happen), they will not be able to turn green again. They have lost the battle and will eventually fall off after curling and wilting. This doesn’t necessarily mean the end for the sunflower plant. However, the leaves help to photosynthesize, so the plant may grow much slower and less efficiently.
Wilting and Curling
The further into the illness that the sunflower goes, the more signs it will show. Once the leaves go completely yellow, they will become extremely weak and start curling in and wilt. Surprisingly, this is a last ditch effort to save the plant.
As mentioned, the plant will stop trying to save the weaker areas (the leaves) as it focuses on keeping the rest of the plant from dying.
Prevention and treatment of yellowing sunflower leaves
The best way to mitigate these conditions is by planning and taking preventative measures before they even begin. Let’s look at all the things that can be done to ensure that your sunflowers have a good head start and continued stability throughout their growing journey.
Prevention Measures
Plant sunflowers in an area with plenty of sunlight
All plants need sunlight to grow. Their chlorophyll stores absorb the sunlight and convert it into usable energy in combination with water from the soil and carbon dioxide from the air.
This process is known as photosynthesis. Without adequate sunlight, the plant will simply not grow. Given that sunflowers grow so tall, they require an abundance of the sun’s rays to just reach their height.
Furthermore, their large flower heads and stems also need a ton of sun to allow them to form fully. Choosing a location to plant with an abundance of the unhindered sun is extremely important. The best location is in open fields or in the middle of an open garden.
Water sunflowers regularly, but do not over-water
Sunflowers like short, sharp bursts of water. They do prefer slightly more when germinating but once established, they only need to be watered once a week until the top 6 inches of soil is moist. Avoid overwatering at all costs.
Use a balanced fertilizer to ensure plants have sufficient nutrients
The best fertilizer for sunflowers is a balanced 10-10-10 NPK mix. They are heavy feeders during their growing season, so they need some good quality fertilizer to boost their growth. Research has proven that granulated blends work best as they release the nutrients slowly, beginning in spring and lasting through the blooming summer season.
Monitor for pests and diseases and take appropriate action if necessary
Sunflowers are quite resilient to pests. However, they are not immune. Most common pests are large enough to spot and remove as they enter the sunflower growing area. Try to pick off as many as possible and discard them thoroughly.
Diseases can be avoided by providing optimal growth conditions. This includes adequately draining soils, avoiding too much water, spacing them with enough space to prevent humidity and air circulation issues, etc.
How do you fix yellow sunflower leaves?
When a sunflower’s leaves turn yellow, it’s always best to try to correct the underlying issue before it completely establishes itself. Let’s have a look at some simple fixes to heal your sunflowers and ensure they thrive:
Overwatering:
- Prepare with soil that drains well, e.g.: Loam-based (sand, silt, and clay) with mixed composted (aged) manure.
- Remove the affected areas
- Allow the plant to completely dry out
- Scale back on the water
Pests:
- Remove them if possible
- Use an organic insecticide such as vegetable oil spray (2 grams of either safflower, peanut, sunflower, or soybean mixed with one cup water and use as a spray) or neem oil.
Disease:
- Prune away damaged limbs with a clean, sterilized pair of gardening shears or scissors.
- Remove the plant from its container or soil
- Create a new batch of soil that is loam based and blended with rotting compost or manure.
Frequently Asked Questions (FAQs)
What do overwatered sunflowers look like?
The first thing you’ll notice with an overwatered sunflower is its leaves fading into a yellow tinge. On closer inspection, you will see that they may begin to curl inwards and become droopy. The stems/stalks will weaken and look almost slightly bendy.
Lastly, you may notice that the soil is clumpy and has a foul odor. The roots are the first to rot with excessive water. The disease will work its way up the stem and outwards in the leaves.
Should I remove the yellow sunflower leaves?
It’s recommended to remove yellow leaves with clean cuts at the stem. This will allow the sunflower to focus its energy on growing more green leaves instead of trying to keep the decaying ones alive.
Can a yellow leaf turn green again?
When the leaves of a sunflower plant turn yellow, the plant will essentially abandon it and attempt to regenerate other areas of the plant. As a result, the leaves will not turn green again.
Does overwatering cause yellow leaves?
Yes, overwatering is one of the reasons why a plant’s leaves will turn yellow. Overwatering is one of many stress reactions that force the lush leaves to fade into yellow before curling, wilting, and then dropping off.
What deficiency causes the yellowing of leaves?
Yellowing leaves can present themselves in 2 different ways when there is a nutrient deficiency. When the plant lacks nitrogen, the older leaves on the inside are the first to turn yellow, and the younger outside leaves will follow as the issue persists. When the plant lacks potassium, the leaves’ center generally stays green, but the edges turn yellow.
Conclusion:
Like any problem that plants face, there is always a root cause. It’s generally some type of stress. When a sunflower’s leaves begin turning yellow, a small handful of issues could be out of balance.
Anything from overwatering to nutrient deficiency to pest attacks or diseases can cause this kind of stress.
Understanding the root cause will go a long way in healing the sunflower and helping it thrive. We hope that this guide has been helpful. You can read about similar topics here on our website. Check back again soon for more.
