From your living room to your yard, plants with rich green leaves beautify your world. But sometimes, when you least expect it, your prized plant leaves turn yellow. Known as chlorosis, yellowing happens when something interferes with your plants chlorophyll — thats the plant pigment behind that gorgeous green you love.
The good news is yellow leaves are a call for help. Answer the call and take the right steps, and you can fix yellow leaves and prevent their return. Most yellow leaves trace back to one of these problems:
Sunflowers are one of the most iconic and recognizable flowers, known for their large, vibrant yellow flower heads However, if you notice the leaves on your sunflowers turning yellow, it can be cause for concern. Yellowing leaves on sunflowers can indicate a few different problems, but the main causes are cultural issues, pests, and diseases. Let’s explore the most common reasons sunflower leaves turn yellow and what you can do about it.
Nutrient Deficiencies
One of the most common reasons for yellowing sunflower leaves is a lack of nutrients in the soil. Sunflowers are heavy feeders and require sufficient levels of nitrogen, phosphorus, and potassium for optimal growth and flowering. A nitrogen deficiency will cause the lower, older leaves to turn yellow first, eventually progressing up the plant if left unchecked. Yellow mottling from lack of phosphorus starts on the lower leaves as well. And potassium deficiency shows as yellow leaf edges and tips.
Before assuming a nutrient deficiency it’s a good idea to test your soil pH, as sunflowers prefer a slightly acidic pH between 6.0-7.5. Improper pH can prevent the plant from absorbing nutrients efficiently. Aside from pH poor drainage or overwatering can also contribute to nutrient issues.
The solution is to amend the soil with a balanced fertilizer before planting and side dress growing plants with additional nitrogen as needed. Compost and manure will also help provide a slow-release source of nutrients. And be sure to water thoroughly but allow the soil to dry slightly between waterings.
Environmental Stressors
Factors like extreme temperatures, drought, flooding, or wind damage can also cause sunflower leaves to turn yellow. Excessive heat can scorch leaves, while cold snaps can create chlorosis. Drought stress leads to dehydration, but overwatering has a similar effect by depleting roots of oxygen. Physical damage from wind whipping leaves around can disrupt chlorophyll production.
When environmental conditions are the culprit, focus on protecting plants from temperature extremes by providing shade or planting at appropriate times. Water carefully and evenly. Stake taller plants if wind is an issue. Sometimes leaf damage is unavoidable during weather fluctuations, but the overall health of the plant may not suffer too much.
Diseases
There are several common sunflower diseases that first manifest with yellowing leaves, such as:
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Downy Mildew – Caused by the fungus Plasmopara halstedii, downy mildew appears as mottled yellow patches on upper leaf surfaces. Gray fuzz will develop on the undersides in humid conditions.
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Verticillium or Fusarium Wilt – These fungal wilts cause inner leaf yellowing and shriveling. Lower leaves are affected first.
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Sclerotinia or White Mold – Large yellow patches form on leaves as the fungus spreads. White fuzzy mold develops during wet conditions.
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Bacterial Leaf Spot – Angular yellow lesions eventually turn brown. Leaf undersides develop a sticky exudate.
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Sunflower Rust – Reddish brown bumps appear on yellow leaf spots. Rust is worse in humid, rainy weather.
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Viral Diseases – Viruses like sunflower mosaic virus cause mottling, stunting, and deformed growth.
Prevent fungal and bacterial diseases by rotating crops, cleaning up debris, and planting resistant varieties. Avoid overhead watering. Treat rust and mildew with fungicides. There is no treatment for viral diseases – remove and destroy affected plants.
Pests
Sunflower leaves can also turn yellow when infested by certain pests, including:
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Aphids – These tiny sucking insects cause yellow stippling and distortions. Honeydew secretions may coat leaves.
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Spider Mites – Microscopic mites cause stippled yellowing and webbing on undersides of leaves.
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Flea Beetles – Small black jumping beetles chew tiny holes and pits in leaves, causing them to look yellow.
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Head-Clipper Weevils – Weevils make scattered holes in leaves while feeding, which disrupts chlorophyll.
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Cutworms – Leaf-eating caterpillars can quickly defoliate young plants, causing sudden yellowing.
Many pests can be controlled with sprays of insecticidal soap, neem oil, or spinosad. Attract beneficial insects like ladybugs and lacewings to your garden for natural pest control. Row covers can exclude some pests when plants are young.
When to Worry
Mild yellowing on a few lower sunflower leaves is normal as the plant ages. But if yellowing is severe and spreading upward on the plant accompanied by wilting or stunting, it likely indicates a more serious underlying problem. Catch issues early by inspecting leaves frequently for any symptoms. Proper site selection, soil preparation, and maintenance will also help avoid many causes of yellow leaves.
With their bright flower heads and tall stature, it’s no wonder sunflowers are so popular to grow. Paying attention to leaf color and care tips will help you have success with these heat-loving annuals. Don’t hesitate to take action if you notice your sunflower leaves turning yellow so you can enjoy their signature blooms.
Poor Drainage or Improper Watering
Water issues — either too much or too little — are the leading reason behind yellow leaves. When your plants soil is overly wet, roots cant breathe. They suffocate, shut down and stop delivering the water and nutrients plants need. Underwatering or drought has the same basic effect. With too little water, plants cant take up essential nutrients. Before you know it, you have yellow leaves.
To fix or prevent water-related problems, start with your soil. In your yard, avoid planting in low-lying spots or where rain or irrigation puddles stick around. Improve your native soils health and structure to provide the well-draining soil plants need. Pennington Rejuvenate Natural & Organic Garden Soil Mix revitalizes native garden soil with essential plant nutrients and Earth-friendly ingredients like earthworm castings, bio-stimulants and sustainably sourced peat to create a soil environment that nurtures plant roots.
If you grow in containers, choose pots with good drainage holes and keep saucers free of excess water. Use a premium potting soil mix designed especially with containers in mind. Pennington Rejuvenate Premium All Purpose Potting Soil Mix combines the same nourishing, revitalizing ingredients found in our garden soil mix, plus a wetting agent and water-holding crystals to help you optimize your water and break the cycle of too little and too much.
Before you water, give your soil the “finger test.” (Moisture meters work too, but this is more fun.) Just stick your index finger a few inches into the soil. As a general rule, water only when soil feels dry. Then water thoroughly and deeply. If soil feels cool and moist, wait a few days. Always allow soil to dry slightly before you water again.
Root Damage or Compacted Roots
Root damage happens in lots of ways, from wayward trowels or shovels to root rot and other disease. Once damaged, roots may struggle to deliver what your plant needs. Outdoors, compacted landscape soil inhibits the movement of water, oxygen and nutrients. When container plants outgrow their pots, compacted roots result. In both cases, roots cant function properly and yellow leaves reveal the problem.
With in-ground plantings, improve soil structure and compaction by incorporating Pennington Rejuvenate Natural & Organic Garden Soil Mix into your planting site. Garden gypsum can also improve soil compaction, especially in heavy clay soils, and help keep leaves green.
To check containers for damaged or compacted roots, gently slide your plant out of its pot. If its large, get a friend to help. Then turn the container — gently — on its side and ease the root ball out. (Youll get an up-close and personal look at soil moisture, too.) Healthy plant roots are whitish-yellow. Dark, rotting roots smell foul.
If roots are rotten and diseased, its time to consider a new plant. If compactions the problem, prune unhealthy roots, gently loosen roots and repot in a larger container with Pennington Rejuvenate Premium All Purpose Potting Soil Mix.
When soil pH gets out of balance, pH-induced nutrient deficiencies cause yellow leaves.
If youre growing container plants and feeding regularly with premium plant fertilizers like our Pennington Rejuvenate plant foods, soil pH probably isnt the cause of your plants yellow leaves. But if yellow leaf problems are popping up in your yard and garden plantings, soil pH may be the key.
Soil pH influences whether plants can access nutrients. Nutrient availability changes as soil pH moves up or down the pH scale. Most plants, including garden veggies and pollinator-friendly flowers, do best with soil pH in the neutral to slightly acidic range, near 6.0 to 7.0. Acid-loving plants like rhododendrons and blueberries prefer soil near 4.5 to 6.0 pH.
When soil pH becomes lower or higher than a plants optimal range, some preferred nutrients become less available to it. Even though nutrients are present, plants cant take them up — that includes nutrients from fertilizers you add. Leaves turn yellow and stay yellow until pH issues get fixed.
A simple soil test eliminates the guesswork (and stress-work) so you know where your soil pH is at. Most soil testing labs also give recommendations for soil amendments to restore pH balance. Once pH is fixed, nutrients are freed up again and green leaves are back on track.
Leaf patterns of chlorosis provide clues to nutrients your plant needs.
Why Are My Sunflower Leaves Turning Yellow? – LearnToDIY360.com
FAQ
How to fix yellow leaves on sunflowers?
- Remove and destroy any affected plants immediately. Do not put them on a compost heap, as this will contaminate the compost.
- No chemical controls are available.
What does an overwatered sunflower look like?
An overwatered sunflower will exhibit symptoms such as yellowing or browning of leaves, wilting, and potentially mushy or rotten stems. The soil will also appear soggy and may even develop a foul odor.
Do yellow leaves always mean overwatering?
Leaves Turning Bright Yellow or Mushy Stems
This is usually a sign of overwatering, either caused by watering your plant before it’s ready or if your plant is in too low of light. When plants sit in waterlogged soil, their roots can’t get enough oxygen, leading to root damage which manifests as yellow leaves.
How do I stop my plant leaves from turning yellow?
Unless you regularly replace soil nitrogen with fertilizer applications, nitrogen deficiencies turn lawns and plant leaves yellow or pale green. If nutrient deficiencies are to blame, proper fertilization and premium plant foods can help.