Root Awakening: Plant's leaves yellowing due to lack of water

Straits Times

23-05-2025

Check soil moisture level to see how thirsty plant is
I have been growing this plant for a few months. After I transplanted it to a bigger pot, the leaves started turning brown and yellow. I water it daily. What is wrong?
Lee Teck Tiam
The leaves may be yellowing due to a lack of water.
Water your plant early in the day and, at the end of the day, stick your finger beneath the growing mix's surface to feel for moisture. If the soil is dry and the pot is much lighter, your plant has likely taken up all the water.
Larger plants have higher water requirements. The volume and type of growing media you use determine the amount of water retained by your plant, so you may need to move your plant into a bigger pot. Prune it slightly to reduce the number of leaves and the amount of water lost through transpiration.
You can also move your plant into a slightly shadier location to reduce water loss and intake. However, do not move it into deep shade.
Semi-hydroponics suits many foliage houseplants
I am looking to transition my houseplants from potting soil to Leca (light expanded clay aggregate). I have aroids and spider plants. Do you have any advice for creating a semi-hydroponics set-up in Singapore's climate?
James Tan
A wide range of foliage houseplants adapt quite well to being grown in self-watering systems like semi-hydroponics. You can refer to numerous online videos that demonstrate how you can start such a system.
Choose plants that can withstand root disturbance, as moving them over will involve removing existing growing media and cleaning the roots. Ideally, your plants should be able to grow their roots quickly.
Although it may be tempting to use clear containers for semi-hydroponics, these will allow light to penetrate the root zone, which can lead to algae growth. Apart from being unsightly, algae can rob nutrients from your plants.
Finally, avoid placing containers near direct sunlight, as heat build-up will be detrimental to root health. Self-watering set-ups are often used for shade-tolerant plants which can thrive in cooler, shadier conditions.
Ensure plant has enough sunlight and air circulation
What has happened to the new leaf of my Pothos? I bought it three weeks ago and it unfurled like this. The rest of the plant seems healthy. Also, the bottom leaves are dark green but the rest of the leaves are much lighter. They are all roughly equal in size. Is there a reason for this?
Sam Yeo
This aroid species, though shade-tolerant, needs good light to grow.
PHOTO: SAM YEO
The appearance of the new leaves, especially the newest one, could be the plant adapting to its new surroundings. It will take some time for normal growth to resume.
The aroid species you are growing, although shade-tolerant, still requires good light to grow. A lack of light can cause developing leaf tissues to be soft and fragile, and prone to damage and infection.
Also, is there enough air circulation around your plant? Air circulation is required for plants to grow and develop properly.
Make sure your plant gets four to six hours a day of filtered sunlight, which casts a fuzzy shadow. Grow lights can also be used to supplement your plant's light requirements. A small fan in the growing area can also be installed to move air around.
Plant needs a bigger pot and protection from rust disease
Consider providing this grape plant with light shade during hot, dry weather.
PHOTO: JOHN LEE
What are the growing conditions necessary for my new grape plant to flower and fruit in our local climate?
John Lee
Grape plants are climbers and can grow quite large. You will eventually need to transfer it to a bigger container. Avoid planting it in the ground, as waterlogged conditions during the rainy season can kill the plant.
You may need to provide this plant with light shade during hot and dry weather. You will also need to protect the leaves from rainfall. This can help to reduce the likelihood of rust disease, a common issue with this plant. Spraying with copper soap can also help prevent this fungal disease.
As for flowering and fruiting, plant trials are required to see if the cultivar you have will be productive, as the information available is largely based on cultivation in temperate climates.
Lady's Finger may lack nutrients
Fertilise this plant regularly and check for any pest infestations.
PHOTO: LEE CHEE CHEE
Is my Lady's Finger infested or lacking in nutrients?
Lee Chee Chee
The chlorosis in the lower, older leaves seems to indicate a lack of mobile nutrients such as magnesium. Give your plant fertiliser with magnesium on a regular basis. If you are using well-draining soil, the nutrients may be quickly leached away and you will need to feed your plant more often. Soil improvement can be difficult to perform on existing plants without disturbing their roots.
Check if your plant is infested by sap-sucking pests like leaf hoppers, as the leaves have mosaic patterns and distortion common to infestations. Leaf hoppers can spread viral diseases with no cure. Use pesticide to reduce the pest population and limit any damage.
Answers by Dr Wilson Wong, an NParks-certified practising horticulturist and parks manager. He is the founder of Green Culture Singapore and an adjunct assistant professor (Food Science & Technology) at the National University of Singapore.
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