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Why are the tips of new growth turning yellow?

Why Are The Tips Of New Growth Turning Yellow?

Why Are The Tips Of New Growth Turning Yellow? Ok, firstly, this is a very very broad question, and to answer it, for absolutely every plant on Earth, in a short article is a bit impossible. There are however a few basic rules that we can follow to work out what the problem is.

Humans tend to grow a pretty basic subset of plants, and, the reason we grow these is that they are easy to grow and universal rules apply. So if you are a plant geek, growing some weird insectivorous plant from Puerto Rico that turns yellow when it does not eat its favorite wasp, this article is not for you. But if your tomato, cabbage, or spinach plant is getting a yellow tip, this is an article for you.

Years ago, when I was a kid, I got interested in plant mineral nutrition. This led me to a book by a rather intelligent German chap, Dr. Horst Marschner. His books, of which this is an example, are rather essential if you want to understand plant nutrition in a detailed fashion. He is a complete genius, and his writing is engaging, mind-blowing, and very, very educational.

What is Chlorosis? (Yellowing of Leaves)

When leaves get yellow patches it is called chlorosis. If we would want to be a bit more specific, chlorosis can be defined as the yellowing of leaf tissue due to a lack of chlorophyll. Chlorophyll is the pigment that makes photosynthesis possible – in this regard, if your leaves, the solar panels of the plant, go yellow, and photosynthesis becomes impossible – we have a big problem and a potentially deadly plant on our hands.

What causes chlorosis?

Chlorosis can be caused by several factors, lets’s list a few of the more common ones:

  • Nutrient deficiency

A deficiency of certain nutrients can cause the leaf to turn yellow. Depending on which nutrient it is, the leaf will take on different yellowing patterns. 

In my opinion, if you have healthy soil, your plants should be able to find the nutrients they need. The more organic matter, and biological action in your soil, the more available nutrients become. However, if you have not built your soil up properly there are a few things that can cause a nutrient deficiency that causes the tips of plants to turn yellow.

  • Sulfur deficiency

Typically, if new growth is turning yellow, the most likely nutrient that is lacking is sulfur. If you find that older leaves are turning yellow, and some new leaves are not, then the likely cause is a nitrogen deficiency. But generally, a textbook case of new shoot yellowing is a sulfur deficiency.

You can easily correct a sulfur deficiency with chicken manure – from what I understand, the chicken feed contains quite a lot of sulfur (many calcium sources used to provide calcium in the feed will be potentiated by the chicken’s gut activity, and in the manure becomes a special magic formula for plants). Something like Charlie’s Compost appears to be a good source of sulfur if you do not have access to your chickens to make chicken compost.

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They are certified organic so you need not worry about pesticide and antibiotic residues in the manure, and the manure is active – it contains beneficial microbes. I would apply this as per the suggested rates on the bag at the base of plants that show leaf tip deficiency and you should solve the problem.

  • Nutrient excess

In many cases, too much of a nutrient can cause similar effects to too little. As an example, a deficiency of Nitrogen can cause leaves to yellow – but too much Nitrogen can cause a very similar effect.

If you get carried away with chemical fertilizers you can easily burn a plant – in this case, the whole plant turns yellow and looks terrible. This will include leaf tips, stems, main leaves, and so on. But that sort of means that if you were looking for something that causes just the leaf tips to turn yellow, you are probably going to want to read the sulfur deficiency paragraph again, as nitrogen excess is not the answer.

In general, if you follow the instructions on your fertilizer and amendment labels, you should not have to worry about these symptoms. If you add too much fertilizer, you will see your plants go yellow – I find watering them to rinse the nutrients out of the potting soil can help.

Nutrient excess normally causes all leaves to turn yellow – not just the leaf tips, so I think we can rule out nutrient excess when asking “Why Are The Tips Of New Growth Turning Yellow?”

  • Pest damage

Pests such as spider mites, aphids, thrips, and whitefly can cause damage to the leaves that cause extreme yellowing. These pests can also act as vectors for fungal and viral infections that further exacerbate problems.

We often find that when a spider mite or whitefly outbreak occurs, the leaves will take on a mottled yellow look – if you look under the leaves you can see either the webs and mites of the spider mites, or you will see the whiteflies in their various stages. Neem oil is my go-to here, and I also introduce parasitic mites such as Persimilis mites to control the spider mites.

More often than not, spider mite-induced yellowing occurs on older leaves and progresses to young leaves as the mites multiply. Hence the cause of young leaf tips being yellow is unlikely to be spider mites.

  • Viral problems

Pests can transmit certain viruses such as mosaic viruses that cause yellowing of the leaves and eventual death of the plant. For plants such as tomatoes, if I detect mosaic virus I just remove the plant. I don’t need that trouble in my life. The virus sticks to your hands and everything susceptible ends up infected in your garden with time. Here is a nice little video on how to identify the tomato mosaic virus.

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There is a counter wisdom that I have used in certain patches of my garden where I ignore tomato mosaic virus. In this one patch, I allow wild cherry tomatoes to come up each year, and I have noticed that the ones that make it to the end of the season then produce the seeds that germinate in the soil the next year. Over the past 10 years I have noticed that this wild cherry tomato that grows in my garden has become essentially completely resistant to tomato mosaic virus.

If I did not love crimean black and rainbow oxheart and yellow pear tomatoes so much, I would probably just rely on this little wild tomato. Sadly the fancy ones I mentioned are all quite susceptible to viruses.

Again, viral problems are more evident in older leaves in my opinion. As the infection gets worse, the whole plant turns yellow. But at the beginning of the infection, older leaves show signs first and it migrates to younger leaves.

Why Are The Tips Of New Growth Turning Yellow? As we can see from the above, the cause is unlikely viral. Probably a nutrient defficiency, and probably sulfur.

  • Fungal problems

Unlike viral problems, fungal problems can often be controlled. There are many different fungal problems, and I will just list the two that I have the most experience with. These are probably the most common:

  • Powdery mildew

This is an irritating fungal infection that I find gives me particular problems with my squash, cucumber, cannabis (its legal to grow a few plants where I live), and sometimes my tomatoes. For most of the other plants I grow, this is not a problem pest.

It appears as little circles of white fluff on the tops of the leaves and spreads rapidly. As the circles spread, they eventually take over the whole leaf, and in plants such as squash this will kill the leaf. Over time I have bred squash varieties that are less susceptible to this pest in my garden, and I am now proliferating these seeds to other growers in my area. Each year my pumpkin and squash yield increases by quite a significant percentage as these resistance genes get more and more entrenched.

I find that powdery mildew in my area is often a symptom of other pests that are damaging the plants, such as whitefly and spider mite. These pests puncture the leaf cuticles and make it more susceptible to invasion by fungi. Having a healthy population of biocontrols in the garden seems to help reduce the pests, and the powdery mildew problem.

It also helps to open your garden up a bit so that wind can blow through the plants – this keeps humidity down and helps to control powdery mildew. When you have moist, warm, humid, windless days this pest can get out of control in susceptible plants.

You can also spray plants with agents such as neem oil, copper fungicides or sulfur fungicide.

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I prefer to avoid sprays as much as possible, and just let my plants evolve powdery mildew resistance over time. By keeping seeds from the end of the season, you keep the ones that made it through the outbreak and probably carry resistance genes.

Why Are The Tips Of New Growth Turning Yellow? Most likely not powdery mildew as this affects older leaves first.

  • Rust

These are pretty specialized fungi that attack specific closely related plants. The only rust I have ever had problems with is the Fava Bean Rust (Uromyces viciae-fabae). Over the years I just keep fava bean seeds from plants that do not display rust. This has led to a seed bank that I now have where about 30% of every crop gets a bit of rust and the rest make it through with no symptoms. In a few more years this percentage of problem plants should decrease further.

I have a general problem with applying toxic fungicides in my garden as I am worried about the damage to the soil fungi, and also myself and loved one who eats produce from our garden. Hence, if, and that is a big if, I do use a fungicide, it will normally be a sulfur fungicide as I believe these have a relatively benign effect.

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Why Are The Tips Of New Growth Turning Yellow? I have seen rust cause young leaves to turn yellow, normally as the plant gets ready to die completely. But you will see that the rest of the plant looks terrible at this point, so it is unlikely that the leaf tips turning yellow question is answered by it being rust.

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How To Save Your Tips Of New Growth Turning Yellow

More often than not, the tips of plants turning yellow is a sulfur deficiency. Adding some good quality chicken manure compost will solve this problem and provide a bioavailable source of sulfur that is not pH locked or any other problem. 

Tip 1: Fix any nutritional deficiency in your soil

Nutrient deficiency is a leading cause of stunted plant growth and poor crop yields. While growing plants, pay close attention to the soil pH. A soil pH of 6.5 or higher is considered optimum for most plants, but check the ideal pH for the specific plant you are growing.

Some of the most common nutrients are iron, zinc, copper, manganese, boron, magnesium, sulfur and potassium. These nutrients can be found in a wide variety of plant foods. Take a soil test to determine if your soil is deficient in any of these nutrients.

If it is, you can add the missing nutrient to your soil. Apply an organic fertilizer or compost tea to your soil. These organic materials can add nutrients to your soil. Again, when in doubt, use chicken manure!!

Tip 2: Mulch around your plants

Mulching is one other way you can save the tips of new growth turning yellow. Mulch keeps the soil moist, keeps the temperature in the soil constant, and prevents the soil from drying out. A layer of mulch will also prevent the roots of your plants from being exposed to the sun. Mulch will also help to prevent diseases from spreading to your plants.

Keep the soil moist.  If your plants are growing in pots, keep the soil in the pots wet. If you are growing your plants in the ground, keep the soil in the soil moist but not wet. You should water your plants at the same time that you are fertilizing.

Keep the plants from getting too much water. Plants will need to be watered regularly but not overwatered. Overwatering will drown a plant in a poorly drained soil, and starve a a plant in a well drained soil by washing nutrients away.

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Final Thoughts

Leaves turning yellow, or chlorosis is a problem with many causes. The tips of new growth turning yellow is a pretty closely correlated to a sulfur deficiency. Most other causes of yellowing will cause other symptoms and growth tip yellowing.

Hence if it is just the growth tips turning yellow, you can fix this problem by providing a bioavailable source of sulfur such as that which is found in chicken manure.

FAQs

Why are my new growth leaves turning yellow?

Yellow growth shoots are typically a sign of a sulfur defficiency.

Why are my tips turning yellow?

Most likely due to a sulfur defficiency.

How do you fix yellow leaf tips?

To fix the yellow leaf tips, provide the right nutrients and growing conditions, for example, fertilize with a complete fertilizer containing phosphorous, potassium and nitrogen and of course sulfur. I like composted chicken manure which provides all of these. Try to source an organic manure so that you do not bring pesticides and antibiotics that were applied to the chickens into your garden.

Does new growth leaves turn yellow?

New growth leaves usually turn yellow when they are not receiving enough light or when they are receiving too much light. To fix this, provide the right nutrients and growing conditions for your plants.

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