To see yellow spots emerging on a beautiful, fruit-filled branch can be a gardener’s greatest anguish. While growing plants is considered a relaxing hobby, that doesn’t mean problems won’t crop up.
The condition that leaves your seedlings in this state, and which can indicate a variety of health problems, is called chlorosis. It’s like a persistent cough in humans: it means you’re not well, but it may be too broad a symptom to diagnose the specific illness.
Its cause is the visible result of too little chlorophyll – the pigment used to capture sunlight for photosynthesis. Because it gives the leaves their green color, its lack leaves vegetation a pale green, yellow, or even yellowish white.
Since chlorophyll is key to seedlings’ food-producing abilities, seedlings suffering from chlorosis are life-threatening. If you know what to look for, a few variables about how the condition develops can offer a surprising amount of information. Check out:
1. Nutrient deficiency
This is a common reason for chlorosis. Plants need more than a dozen mineral nutrients to survive, and all must come from their roots. Therefore, one soil test it’s the best way to know what you’re missing.
A quick look at the sheets can also clarify the situation. Nutrient-deficient seedlings have distinct patterns of chlorosis, such as green veins with yellow tissue in the middle, which first appear on specific leaves.
Some deficiencies cause older leaves to turn yellow first, and in others the traces start on new growth. This is because a plant can move certain nutrients from leaf to leaf as needed.
When the branch has a low amount of some mobile nutrient – such as nitrogen, phosphorus, potassium, magnesium and nickel – it can transfer the element from its older leaves to help their growth – at least for a while. That is, the old foliage turns yellow, and the shoots green.
On the other hand, an immobile nutrient – such as iron, calcium, boron, copper, manganese and zinc – however, is essentially trapped in the older leaves. If a seedling runs out of iron, it will develop chlorosis on the new shoots, while the previous ones remain green.
Once you’ve narrowed down the suspects to mobile or immobile nutrients, look for more clues as to how the leaf is turning yellow.
Nitrogen and potassium deficiencies appear in older leaves, but while the former is relatively uniform across the leaf and its veins, the latter tends to start at the edges and in the spaces between the veins.
See too
The yellowing of the new parts may indicate iron or calcium chlorosis – the lack of iron being characterized by being uniform with small green veins.
2. Pests
Unlike the previous problem, whose symptoms are often symmetrically distributed in plant tissue, pests tend to develop in asymmetrical patterns. This includes insect damage and leaf spot – a common indication of fungal or bacterial diseases in vegetations.
But we have good news! You damage done by insectswhich result in chlorosis on affected leaves, can be safely contained with non-toxic methods – such as insect repellent twigs, neem oil and DIY organic pesticides.
As water is one of the main sources of survival for seedlings, many end up weighing the quantity by hand, which can create favorable conditions for fungal pathogens. There are several safe ways to control them, from crop rotation until apsodium bicarbonate spray. However, start by monitoring soil moisture.
3. Water and electricity
A insufficient and excessive watering, even without harmful fungi, can lead to discoloration of the leaves. Too much water makes the foliage soft and limp, while the leaves of dehydrated plants are usually dry and brittle.
To understand which of these scenarios put you at risk, observe whether the soil surface has water accumulation and vice versa.
Certain types of soil drain water slowly, which can also cause seedlings to drown. Solve this by growing them in a raised bed – Hugelkultur style, old German technique – or adding sand to the soil.
Damaged and compacted roots are another common cause of chlorosis, so give it enough room to grow in soil or in a container and protect the roots when transplanting.
Don’t forget the sun! It doesn’t matter if watering and nutrients are controlled if the branch has little sunlight – which can cause its leaves to drop and wither.
Many garden vegetables, such as tomatoes and cucumbers, need at least eight hours of sun a day, preferably 10. Broccoli and leafy greens, on the other hand, can survive in significantly less direct sunlight per day. But lighting needs vary between species.
*Via tree hugger