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While succulent yellowing can be stressful, leaf yellowing (chlorosis) is generally caused by one of five factors related to plant care.
Lighter tissue on an otherwise green plant usually marks the beginning of chlorosis. Chlorotic leaves are more prone to burning and leaf diseases and may kill the affected plant if not addressed. Poor root health or a nutritional imbalance is commonly the cause.
This article explores, in some depth, the five possible causes of chlorosis in succulents.
Possible Cause 1: Poor Succulent Root Health
I put this first since it is the most frequent factor in the yellowing of leaves in all houseplants. Yellowing leaves are frequently (though not always) a sign of root distress, and yellowing leaves are most commonly a sign of lack of root oxygen availability.
Healthy soil offers a favorable environment for the growth of plant roots. A favorable growing environment includes access to nutrients, air, moisture, and symbiotic connections with microbes.
Effective soil depends on a balance between moisture and air availability. Other aspects of soil health include:
- Nutrient management – an ability to store and release essential plant nutrients
- The most undervalued attribute – a hospitable environment for soil microorganisms
- Plant requirements for acidic or alkaline soil (pH requirements)
- Plant anchorage – ensuring the media isn’t so light that the plant cannot remain reasonably erect as it grows.
Provided water should move through the soil easily and flow to the bottom of the pot, where it builds up somewhat before draining via the drainage holes. The amount of water retained in the soil is the weight difference between the added and drained amounts.
Your succulent needs regular repotting, which should be done at the start of its growing season – spring for summer growers and autumn for winter growers.
Succulents require suitable soil that offers good drainage in pots that support the soil’s function. Proper drainage prevents root rotting as well as other bacterial and fungal problems. Root-bound succulents will become stunted or develop chlorosis. Repotting also refreshes nutrient availability.
Regardless of your soil’s saturation porosity, which is its capacity to hold air even when flooded, if the water addition and drainage cycles are disrupted, that porosity is lost. Thorough watering followed by complete draining is required for saturation porosity.
Some water (field capacity) is left over after a watering and draining cycle. At the saturation point, the air is still available to the plant roots (saturation porosity).
Water is continuously injected without allowing for a drying period between the saturation stages, compromising porosity and reducing the soil’s ability to hold air.
The biggest cause of death for potted plants is overwatering. Since roots need water and oxygen to survive, they cannot absorb them when submerged in water.
Water should only be used when essential. One can use the following methods to choose when to water:
- Touch the soil: The most accurate test for soil moisture is to feel how dry the potting soil feels. If the mixture is dry at your fingertip after inserting your finger up to the second digit, it needs water. Check at least to a depth of a third of the pot.
- Tap the pot: When potting mix in a clay pot starts to dry up, it shrinks away from the pot’s sides. Use a stick or your knuckles to tap the pot’s side. Water is required if the sound is hollow; if the sound is dull, the soil is moist.
- Estimate weight: It’s easy to see a weight reduction as potting mixtures dry up.
Water deeply when the soil is dry. Fill the pot, ensuring the entire contents are saturated before draining it completely. This process ensures that most of the roots in the bottom two-thirds of the pot receive enough water while removing accumulated salts.
Don’t let the pot sit in the accumulated water; empty the tray after a couple of minutes (not hours).
In compacted soils, fewer large pores, fewer overall pores, and a higher density prevent water and air infiltration.
Because soil compaction makes it more difficult for soil to be moved by an applied force, roots must exert more power to break through the compacted layer, stressing the plant and making it more susceptible to diseases.
The most crucial component of growing healthy plants is your soil. Keeping soil from compacting will:
- Increase water infiltration and storage capacity
- Increase timeliness of field operations
- Decrease the stress on plant roots
- Decrease diseases potential
Gardeners will do well to repot their succulents when they notice soil compaction.
Possible Cuse 2: Nitrogen Imbalance
We all know that nitrogen is a folial booster of note, but often too much nitrogen causes a build-up of salts that can cause leaves to be yellow.
Remedy Soil Salts in Indoor Pots
Consider flushing the soil a couple of times before you decide on repotting your succulent. To remove the salts, saturate and drain the soil repeatedly, allowing it to dry completely before repeating the process a couple of days later.
For the majority (or all) of the salts to be leached out, repeat the procedure three to four times.
Possible Cause 3: Magnesium Deficiency
Magnesium deficiency is another common cause of yellowing leaves, but this is easy to remedy. Leaf yellowing (chlorosis) is most common when temperatures have dropped.
Epsom salt (magnesium sulfate) lowers the pH and provides magnesium and sulfur, two nutrients often deficient in alkaline soils. Benefits of magnesium for your succulent plants include:
- Aids photosynthesis by helping your succulent create chlorophyll
- Promotes healthy cell division and protein formation
- Increases a plant’s ability to retain water
- Allows the succulent to take in and use phosphorus, better
Magnesium has a poor cation exchange capacity (CEC), i.e., it binds poorly to soil particles. The only way your plant gets access to it is if it remains in situ near the roots, so repeat the process every three to four months.
Possible Cause 4: Soil pH and Iron Availability
As soil pH rises over 6.5 to 6.0, iron becomes less accessible to plants. High soil concentrations of other elements, such as calcium, zinc, manganese, phosphorus, or copper, may prevent plants from absorbing iron. Iron availability will also be low in a plant with a potassium deficiency.
Possible Cause 5: Natural Causes
And while we’re stressing about a yellow leaf, may it’s just the end of the road for that leaf, and it’s ready to leave the plant. As your succulent grows, older leaves are replaced by new growth better able to photosynthesize.
To optimize resources, the succulent redirects nutrients to the most productive parts, cutting off supplies to older leaves, upon which the yellow and drop off.
There are several reasons for leaves to turn yellow on succulents. Before relocating the plant, check the root health first, as this is the most common cause of chlorosis of leaves.
If the root system is healthy, then systematically eliminate possible causes, but remember that sudden environmental changes can also cause chlorosis.
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