Q. I am trying to reduce the use of pesticides in my garden in Tando Jam and recently learnt that flowers repel insects. Please tell which insects do they repel. I want to experiment with this to see how effective it is.

A. Not all flowering plants are insect repellent and those that are, each repel only certain types of insects. The most common — and easiest to find — insect repellent plants / flowers / herbs include the following:

To repel aphids: Basil, catnip, chives, coriander, dill, eucalyptus, fennel, French marigolds / tagetes, garlic, larkspur, nasturtiums, thyme, petunias and all mints.

Have you ever thought of growing some insect repellent plants in your garden? While basil repels mosquitos, citronella grass can help deter cats

To repel mosquitoes: Basil, chamomile, lemon grass, lantana, feverfew, lavender, oregano, lemon balm and neem. Against squash / cucumber bugs / beetles: Catnip, dill, fennel, aniseed, petunias, radish and nasturtiums.

For spider mites: Coriander, fennel, dill, aniseed, dill and oregano.

To repel carrot-fly: All members of the onion family including leeks and chives, basil, chamomile, lavender, lettuce, French marigolds / tagetes, oregano, rosemary and tobacco.

The above are just a few examples, and it would help if you read up on the subject of ‘companion planting’ to learn which plants / flowers / herbs / vegetables / fruits benefit from being grown next to each other and why. To help keep a garden free of insect pests, it is good to grow a mix of all kinds of plants in fairly close quarters instead of growing, for example, individual beds of carrots, cabbages, etc. in one area of the garden, and beds of flowers in another. Growing beds of just one species gives insect pests something to hone in on; growing mixed beds of plants acts to confuse an insect’s sense of smell. Some plants also actively ‘feed’ other plant species and, studying ‘companion planting’ should also give you lots of information about this. Good luck, and the sooner you completely stop using any chemical interventions in your garden, the better it will be for all.

Q. I have a problem with seed germination. I had sown seeds of tomato and chillies at the end of February but not a single one came up. I am 12 years old and reside in Abbottabad.

A. The cool — in February cold — climate of Abbottabad does not permit the germination of warm to hot weather seed species. To successfully grow these, along with things such as aubergines and bhindi, you need to wait until the weather has sufficiently warmed up the soil. Please try again now or, if nights are still a bit chilly, wait another week to 10 days (but before May 14 at the very latest, otherwise they will not have a long enough season to produce to their full capacity). If you want to grow earlier crops of these, you will need, next year, to start them off, from mid-March, under plastic covers.

Q. Do plants benefit from sewage water and, if so, to what extent?

A. This depends on the exact source of the sewage water, on if / how it was treated to extract toxins / heavy metals, etc. The problem, here in Pakistan, is that approximately 92pc to 99pc sewage water / municipal wastewater is not treated in anyway. Even in Karachi and Islamabad, studies indicate that no more, possibly less, than 8pc of sewage / wastewater is subject to the biological treatment process intended to make it safe for irrigation purposes. It is true to say that plant growth can be boosted via irrigation with sewage / wastewater but, in the case of fruit, vegetables and herbs, they may then be accumulatively toxic to eat. Such sewage / municipal wastewater, treated or not, is generally known as ‘black water’. Depending on the size of your garden, it may be better to investigate using ‘grey water’ — this is household water recycled from showers / laundry / kitchen, etc which, as long as noxious chemicals / grease are not used, can be recycled for everyday garden use. However, as with any recycled water, precautions need to be taken in order to avoid any possibility, no matter how remote, of harm to human or environmental health.

Q. Which other plants, in addition to roses, can ‘Epsom salts’ be applied to?

A. The vast majority of plants, both edible and otherwise, will benefit from suitably diluted applications of ‘Epsom salts’ — the dosage varying from species to species. Apologies, but it is not possible to list exact doses per species here as the list is extensive.

Q. Kindly explain, clearly, what the words “if the runners have well-developed root systems of their own” mean.

A. Some plant species, strawberries for instance, do not only reproduce by seed / root division but also by sending out ‘runners’. They are long, often (but not always) ground hugging, new stems that, in places, will themselves grow leaves and then their own roots into the soil. In the initial stages, these delicate roots are not strong enough to sustain the ‘baby’ plants which have formed, and the ‘baby’ plants remain attached, by the long stem — the ‘runner’ — to the parent plant, which continues to feed them. However, once these ‘baby’ plants have grown strong root systems of their own, the stem / ‘runner’ attaching them to the parent plant can be cut. I hope this answers your question.

Q. Can horseradish be grown in Karachi and, if it can, where can I get plants or seeds?

A. It is being successfully grown, in carefully monitored conditions, in Malir. Plants / seeds are not, to the best of my knowledge and belief, locally available. It would, therefore, be necessary to source your own but, please, do not break our ‘plant protection’ laws in the process. Our indigenous plant species must be protected from imported diseases / pests at all costs.

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

Published in Dawn, Sunday Magazine, April 24th, 2016