Each week The West Australian’s Sabrina Hahn helps home gardeners with their thorniest questions.

This week she’s helping with passionfruit and olive trees, golden cane palms, and reticulation.

To submit your own question to the Green With Envy column, published inside Saturday’s The West Australian, write to Ask Sabrina, GPO Box D162, Perth 6001, or email home@wanews.com.au.

Please include your full name and suburb. Due to the volume of questions, not all of them will be answered.

Matter of height

Q Is there an effective method to limit the height that golden cane palms grow? I have a number of these palms in my garden that are approaching the ideal height for their location and I would like to prevent them from reaching their potential full height of 6 to 8 metres.

Mark Minissale, Woodlands

A Never cut the tops off palm trees to control their height because they have a single terminal bud and cutting will kill the entire trunk of the palm. However, golden cane palms grow multiple trunks, known as canes. You can cut the tallest canes down to ground level, allowing the younger canes to emerge and grow from the base. Many gardeners underprune the lower leaves on golden canes, which gives them a more elegant appearance.

Fruit free

Q We have a very healthy 18-month-old passionfruit vine with plenty of flowers, however, they are all covered in some sort of mite. We think this is the cause of no fruit. We have sprayed two types of product from the nursery with no luck. Can you please assist?

Michael Cox, Dunsborough

A The problem must have occurred during the early bud stage when a sap sucking insect or mites have fed on the sap of the bud. This won’t be the cause of lack of fruiting; passionfruit vines across Australia have been developed from early varieties that are now losing their vigour and fruit production. There’s not much you can do about the problem, except keep the vine as healthy as possible. Add some boron and trace elements in spring.

Olive tree dilemma

Q Read your advice every week and very thankful. As per my pic I have a four-year-old kalamata olive tree in Noranda. Had lots of olives first three years but last year less and then cut the top off as was getting too tall. Once I did that it all died and some shoots growing back now. What do I do now please?

Cosma Nicolau, Noranda

A Most olive trees can be pruned back hard, so it’s not the pruning that’s caused defoliation — but the timing. Notice that the bark along one side of the tree is cracking and peeling; this could be due to the pruning being done just before summer, and the trunk has suffered sunburn. Another cause could be fungal diseases that affect the cambium layer just below the bark. This summer, protect the trunk with shade cloth and in August inject the tree trunk with phosphorus acid like Fos-Inject.

Test the water

Q Your Green With Envy column on June 13 said Jan Barac was worried about using reticulation for 20 minutes twice a week — I thought it was only 10 minutes only once on your rostered day and definitely not during restriction times or am I wrong?

Harry Young, Bayswater

A During the summer, you are permitted to water your plants twice a week on your designated days. Different irrigation systems deliver varying amounts of water due to the differences in nozzles and drip systems, so the watering duration should be based on the total amount of water supplied. During the peak summer period, a drip system that operates for just 10 minutes can lead to quick evaporation, failing to effectively water the root systems of plants. Climate change is changing how we garden; we can no longer just go by traditional the northern hemisphere four seasons. Our summers are longer and our winters are drier. Hand watering is permitted anytime of the year and is always a good option when extra watering is required.