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What to do when Sunflower plant leaves turn yellow & fall off

The leaves of sunflower plants can turn yellow and brown for reasons within or beyond your control. Here are the most common causes and steps you can take to make the foliage of the sunflower plant look green and healthy again.

Underwatering or overwatering is bad for Sunflower plants

Improper watering is usually the main culprit when yellow or brown leaves start to develop on Sunflower plants. Flowering plants like Sunflower plants benefit from deep regular watering. This isn’t just for maintaining the health of leaves but to also maximize the potential of the bloom period. Underwatering Sunflower plants could result in yellow leaves as the plant wouldn’t be able to produce enough energy with a key component (water) missing from photosynthesis.

Overwatering can also damage leaves as excessive moisture can clog the soil and prevent the Sunflower plants from ‘breathing’. Soil drainage plays a key role in this respect.

As a general rule of thumb, we would recommend watering Sunflower plants once a week and increasing or decreasing the frequency of watering according to the weather (e.g. water more if the weather is hot, water less if the weather is cold).

Proper drainage of water from soil

You won’t be able to properly gauge the frequency of watering the sunflower plant needs if it is being grown in soil that doesn’t drain well. Compacted soil can cause a number of issues for sunflower plants such as preventing root growth, reducing nutrient absorption, and preventing oxygen absorption. All of this can cause leaves to turn yellow and fall off. you will know if the soil is waterlogged by creating a tiny hole on the soil surface and filling it with water. If the water hasn’t drained after a few hours then you are dealing with clogged soil problems.

To stop more leaves from turning yellow, you will most likely need to transplant the sunflower plant into soil that drains well. One way of doing this is by mixing the soil with material like perlite, compost, and shredded leaves.

Excessive sunlight or lack of sunlight

Yellow leaves can also form on sunflower plants due to changes in sunlight conditions. Prolonged exposure to direct sunlight, for example, can harm plants because it can result in sunburn and the scorching of leaves. Lack of sunlight could have the same negative effect on sunflower plants as it would result in the leaves not getting enough light to drive photosynthesis. Lack of energy would then cause the leaves to wilt and gradually become discolored.

Try to position the sunflower plant or provide it enough cover or exposure so that it receives an optimal amount of sunlight, which is about 8 hours of full sun per day.

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