Q. I have a problem with leaf miners in my tomato plants. Is it okay to use ordinary fly and mosquito spray on them? The reason I ask is that sprays intended for the garden are very expensive as compared to the fly sprays used in the home.

A. No! The harsh chemicals in household fly / insect sprays will not only damage your tomato plants but also have the inherent capability to poison the tomato fruits: I do not advocate the use of chemicals in any shape or form and this applies to commercially manufactured garden sprays too. It is safer, healthier and much better for the environment as a whole, to practice organic gardening principles.

Leaf miners can be a problem but are not very difficult to deal with: at the very onset of a leaf miner attack, when their tunnels inside the leaf become visible, it is easy to simply squash the leaf miner larvae inside with your fingers. If a leaf has been heavily tunnelled then remove it and dispose of it, sensibly, well away from the garden.

As these troublesome larvae are inside the leaf, sprays, be these of the noxious chemical kind or safe organic ones, are rarely 100 per cent effective. It can be a time consuming task to squash the larvae in the leaves but this really is the best solution. Leaf miners are also attracted to aubergines, pumpkins, cucumbers and squash in general, plus, they absolutely adore chrysanthemums.

Q. The lower leaves, the large ones, on my sweet basil plant repeatedly turn yellow, dry up and fall off. The plant does make lots of new leaves on top but the bare stems look bad on the bottom part. I want the whole plant to remain bushy and green. Please advise what the problem is and how to solve it.

How much pesticide should be used in a garden? Why do basil leaves wither away? Are you over-watering your chikoo tree? The expert answers your queries

A. It is perfectly natural for mature basil plants to shed their lower leaves. Continually picking leaves before they reach their full size — and using them in the kitchen — will encourage the plant to produce more young leaves and help in keeping it looking nice and healthy. Basil leaves and stems can be shade-dried for culinary use. Additionally, when basil seedlings are just four to five inches tall, nip out the main growing tips to encourage bushiness: this keeps the plant smaller and denser and it does not then produce the long stems you mention.

Q. I need to know if basil prefers to be in direct sun, partial shade or shade.

A. Basil loves sunshine and plenty of it. It can adapt to light shade but does not thrive in dense shade at all.

Q. I want to prune my 20-year-old grape vines but do not know when this should be done or how to do it. Please help.

A. Grape vines are generally pruned — in our climate — twice a year: once in summer when long, thin, heavily leafed, new shoots are cut back to allow direct sunshine to ripen the grapes in humid conditions, and then during January / February after they have dropped their leaves. It is this winter pruning which is the most essential. There are many different schools of thought on the winter pruning of grapes but, as a general rule, all woody ‘stems’ are pruned back to just three or four leaf bud points, plus, any dead or diseased wood should be removed too. Do not be afraid of ‘over-pruning’ — the worst that can happen is that you get a reduced crop next time but the odds are that it will be of superior quality.

Q. My sharifas turn black and fall before they are ripe and the flowers keep dropping off the chicoo tree. What shall I do?

A. It could very well be that you are over-watering your trees or not watering them regularly enough. Little and often should be the rule when it comes to watering plants; and it may help to give them a feed of organic, liquid fertiliser, every two weeks from when flower buds begin to form and on until after they have finished fruiting. The extreme heat this summer will not have helped them at all.

Q. What is the reason for putting rusty iron nails in the soil and can they be put in all plants?

A. Iron nails slowly release iron into the soil and this, in turn, is taken up by plant species which need iron. This does not apply to all plants and it is asking for nasty accidents to add iron nails to garden / plant pot soil in general. They should only be used when needed and even then, they must be buried deep in, for example, the holes used when planting trees where they will not be disturbed and where it is unlikely someone will inadvertently disturb them and get hurt in the process.

Q. I have a lot of pot plants, mainly succulents but as my house faces north, they get very little sunlight for most of the year, especially during winter. Recently, many of them have died and I don’t know why.

A. There are numerous possible reasons for your plants to have died: Lack of sunlight, over or under-watering, shortage of soil nutrition, disease. Please provide more details. Thank you.

Please continue sending your gardening queries to zahrahnasir@hotmail.com. Remember to include your location. The writer will not respond directly by email. Emails with attachments will not be opened.

Published in Dawn, Sunday Magazine, September 25th, 2015

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