First-time plant growers can get a bit too excited with their first set of cultivated plants. They tend to spoil them by watering often and fussing over the young plants’ growth as a mother would over her child. However, this could pose risks to young plants that are just developing their first set of true leaves.
First set of true leaves turning yellow: What are the reasons?
1. Insufficient light
Young plants tend to appear yellow or develop yellowing leaves if they do not get enough light. This is usually true if the plants are grown indoors. See to it that they are provided with the right amount and intensity of light. A grow light should be placed directly over the young plants and it should be kept on for at least 12 hours daily.
Too much light could also damage the first set of true leaves, so make sure that it is only exposed for 12 hours every day. It is ideal to invest in a grow light with an automatic timer to save you having to turn it on and off, as is necessary when using a manual grow light.
2. Insufficient water
Young plants with their first set of true leaves may have yellowing leaves if they are not given enough water. They need water to grow healthy and to develop strong roots and plant parts. You do not have to water the plants every day; only when the soil is dry.
3. Too much water
While insufficient water can cause yellowing, overwatering your new plants can produce the same result. This usually happens when there are consistent heavy downpours or if you leave the sprinkler on for a long period.
Below are the common signs of overwatered plants:
- There is no new growth.
- Young leaves appear brownish.
- The soil appears greenish due to the presence of algae.
- The plants begin to wilt.
- The roots are stunted or rotten.
- The lower leaves are yellowish.
Young plants need to breathe well and if they are overwatered they can drown. If the roots are constantly flooded, it hinders absorption of the required gases resulting in the first set of true leaves turning yellow.
4. Overfertilization
Some plant owners make the mistake of overfertilizing their young plants. Ideally, seedlings do not require fertilizer at this stage. If you are fertilizing your young plants, this could be the reason for their yellowing leaves. Avoid using fertilizer and flush out the soil slowly with water.
5. High soil pH
Certain plants, like tomatoes, tend to have yellowing leaves if the same soil is used repeatedly. The pH level becomes high and the soil becomes infertile. The acidic soil is the cause of yellowing leaves, which eventually fall off.
You can do a soil test to ascertain the soil pH; if the reading is lower than 5.5 it means the soil is too acidic. You can add garden lime to the soil to balance the acidity. Ideally, test the soil pH at the start of each gardening year and make adjustments to the soil a few weeks before transplanting your seedlings.
6. Nitrogen or iron deficiency
Plants require nutrients like nitrogen and iron to be able to grow healthily and achieve above-ground growth. Older leaves tend to turn yellowish if there is a nitrogen deficiency, although the top leaves may remain green. To correct this, apply liquid fertilizer with a high nitrogen value and follow the instructions on the package carefully. You can also boost nitrogen in the soil by adding coffee grounds, compost and earthworm castings.
For an iron deficiency, apply a liquid iron supplement or a chelated iron supplement. This can be sprayed on the foliage if mixed with water. You can also add these supplements to the soil.
Aside from the causes mentioned above, your young plants may also be suffering from fungal diseases like early blight, septoria leaf spot, verticillium wilt and fusarium wilt. These fungal diseases can be treated with fungicides. Remove the affected leaves and burn them so that infection does not spread further.
Pests like spider mites and mealybugs may also invade the young plants, so make sure to check the plants often and spray them occasionally with soapy water.
How to prevent the first set of true leaves from turning yellow?
There is still hope for your new plants if you follow these measures:
- Use soil with the right minerals to support the development and healthy growth of seedlings or young plants. This prevents the need for fertilizers during the early stage of the plants’ lives.
- Water the plants regularly but avoid overwatering them to prevent yellowing leaves.
- Provide the right amount of light so the plants will grow healthy.
- If you must apply fertilizer during the early stages of growth, only do so in small quantities.
- Check the plants regularly to ensure they are free from any form of disease or fungal infection.
- Take preventive measures to keep pests away by spraying the plants with a mixture of soapy water now and then.
Conclusion
The first set of true leaves turning yellow could cause panic and worry, especially for first-time plant growers. Common reasons for this could include overwatering, underwatering or insufficient light. However, it could also be due to overfertilization, nutrient deficiency or fungal diseases.
Image: istockphoto.com / ArtRachen01