Give plants more air circulation

My cabbage’s leaves are crinkled and some have developed white spots. The plant gets four hours of sunlight a day and is kept in a hydroponics system. What is wrong?

Adrian Ling

The appearance of crinkled leaves could be a natural characteristic of the cultivar you are growing. But it could also result from insufficient air circulation – this might have triggered the white spots, which are possibly pathogenic fungus.

As the plant grows, there will be less space between the rosette’s leaves, and eventually between this plant and others. Air circulation will worsen.

You can harvest larger plants from alternating spots, to make space for the rest to grow. Otherwise, plant seedlings farther apart.

Citrus seedlings need more light and fertiliser

I germinated these plants from orange seeds and transferred them to a small pot when they sprouted. They seem to have stopped growing. There is plenty of sunlight. What is wrong?

Gloria Ang

Your potted citrus seem to be growing behind a window grille. Plants in the citrus family thrive under full sun outdoors, so give them at least six hours of direct sunlight daily.

Citrus plants also detest wet feet, so ensure the growing mix is well-draining but still moisture-retentive. Do not let them dry out.

Note that wet feet can interfere with nutrient intake and the resulting deficiencies will manifest as yellow or pale green leaves.

For robust growth, fertilise seedlings with controlled-release chemical fertiliser pellets that supply all the nutrition your plant needs. Avoid organic fertilisers, as they may not have the full suite of nutrients needed for a citrus plant to thrive.

Cherry blossom plant needs well-draining soil

I bought this cherry blossom plant during Chinese New Year. Can I repot it? How do I care for it?

Gan Gim Teck

Your cherry blossom plant can be potted in a larger container with drainage holes and well-draining soil. It does not do well in waterlogged conditions, but do not let it dry out.

This plant needs at least six hours of direct sunlight to thrive and can be grown outdoors. If it has been kept indoors for a while, you can move it to a brighter spot, but do so gradually to avoid burning it.

It is not likely to bloom profusely under local conditions, although the occasional cool spell may trigger the production of a few flowers.

The plant may produce some gum on its trunk and branches as it grows. This substance can be harvested and used in peach gum desserts.

Air plant’s broken leaves need not be pruned

My air plant seems mostly healthy, but its bottom leaves are stunted and some are yellowing. Should I remove the leaves?

Janice Toon

The new leaves of your air plant (Tillandsia ionantha) are growing from the centre of the plant.

The lower leaves seem to have been broken, possibly due to rough handling, and will not recover. The brown portions are areas that have healed over to prevent infection from entering the plant.

Was the plant growing in the shade before being moved to a sunny spot? The yellowed leaves could be due to sunburn or another injury.

However, the plant seems to have adapted, as the yellow parts are only on the older leaves, while the new foliage looks healthy.