Q. The leaves of my Dahlia plant have been attacked by some insect that seems to be inside them. The leaves have developed strange lines and have become dry and brittle. Can you tell me what the problem is and how to solve it?

A. The problem is leaf miners: these are the larvae of several kinds of beetle/moth which burrow inside leaves, making tunnels as they go. The easiest solution is to squash the larvae inside the leaves as soon as you see them. Any badly infected leaves are best cut off the plants and disposed of along with the regular household garbage and not in the compost bin.

Q. The leaves of my Dahlia and nasturtium plants have turned yellow and become crunchy. I sprayed them with neem oil and a soapy mixture without any results. Please advise what else to do.

Your gardening queries answered

A. The leaves have died — possibly burnt up by a combination of direct sun, high humidity or wind. If leaves are wet — such as from a morning watering — when sunlight or hot wind hit them, they burn up very quickly as both dahlia and nasturtium leaves are exceptionally tender. This is just one of the reasons that watering at sunset is advisable. Protection from strong winds is suggested for the future too.

Q. When is the best time to sow watermelon seeds in Lahore?

A. April and May.

Q. I live in Rawalpindi and want to know the local name for Lady’s Mantle.

A. Lady’s mantle — or Alchemilla mollis to give it its botanical name — is not a plant of the plains areas of the country but is restricted to just a small number of mountain forest areas in the north. As such, there is no Urdu name for this species. There is probably a name in Pashto or some other language spoken in the north but, unfortunately, I do not know what it is.

Q. What is the best method of watering seeds and seedlings?

A. Use a watering can with a very fine ‘rose’ — the ‘rose’ is the the attachment with holes in it, through which the water is poured. A ‘fine rose’ is one with very tiny holes to lighten the water pressure so that it doesn’t batter tender seedlings or wash seeds out of the soil. Similar attachments are available for hosepipes but using a watering can allows for much more control.

Q. I grew a lemon tree from seed in Karachi. The tree is now six years old and about six feet tall but it hasn’t produced any fruit. It does not receive any sunlight at the spot where it is planted but is now too big to be moved. Is there a way to make it fruit naturally or forcefully?

A. Sadly, the tree is unlikely to ever bear fruit as it needs sunshine — and lots of it — in order to do this. Moving the tree — this can be done if great care and the correct equipment is used — to a sunny spot is the only solution.

Q. How can I grow a perfect walnut tree in Quetta? I have tried and failed many times. I tried growing one from a walnut and tried with a purchased sapling too.

A. Buying another sapling, one of reasonable height and strength, towards the end of next winter is the best way to ‘try again.’ Plant the sapling, in a well- prepared planting hole (instructions have appeared in this column a number of times) made in a carefully selected spot in which the sapling has plenty of soil depth for its roots and space/light to grow to maturity above ground. Walnuts are often huge trees when fully grown. Keep the sapling well watered, especially during the heat of Quetta in summer, until — at the age of perhaps four to five years — it is well established to get by with a far less strict watering regime.

Q. I brought seeds of Delphinium and aciano from the US and need to know if the soil in Karachi is suitable for them. If so, when should they be sown?

A. Both Delphiniums and Centurea cyanus (aciano) can be grown in Karachi. Delphiniums are best sown, in pots/trays of top quality, preferably organic, compost, in partial shade during August/September as they require a long growing season. They can be transplanted into individual pots once large enough to handle and kept in partial shade until the heat subsides towards the end of October, after which they can be transplanted into their final growing position in winter sunshine. Soil must be rich in organic matter and well-drained. Slugs adore them so please take precautions against these pests. They are best treated as annual flowers as they are unlikely to be perennial in Karachi.

Centurea cyanus, better known as cornflowers, are an easy to grow annual flower with seeds, in your location, sown anytime from the end of September to the end of December. They prefer poor to medium, well-drained soil in direct sunlight and are best sown directly where they are to bloom.

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

Published in Dawn, EOS, May 28th, 2017