What to do when Dahlia plant leaves turn yellow & fall off
The leaves of dahlia 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 dahlia plant look green and healthy again.
Underwatering or overwatering is bad for Dahlia plants
Improper watering is usually the main culprit when yellow or brown leaves start to develop on Dahlia plants. As plants that originate from high-elevated areas of Mexico and Central America, dahlia plants do enjoy frequent but light watering. A puddle of water, however, shouldn’t remain on the soil after the plant gets watered as that could encourage root rot to develop and this, in turn, can cause yellow leaves. How often you water the dahlia plant will depend on factors such as whether you are growing it indoors or outdoors and the general humidity, temperature, and light intensity.
On the flip side, underwatering may cause dahlia plants to develop yellow leaves as it may cause interference to the chlorophyll (the pigment that gives leaves their green color) and, in turn, start the discoloration process.
As a general rule of thumb, it should be okay to water dahlia plants once a week. Adjust the watering accordingly as the season changes.
Proper drainage of water from soil
You won’t be able to properly gauge the frequency of watering the dahlia plant needs if it is being grown in soil that doesn’t drain well. Compacted soil can cause a number of issues for dahlia 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 dahlia 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 dahlia 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 dahlia 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 dahlia plant or provide it enough cover or exposure so that it receives an optimal amount of sunlight, which is about six to eight hours of full sun per day.
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