gardening questions answered - editorial - a global garden australia -

	Question & Answer
	topic: nematodes SA question: I have seen a report on ABC Gardening where the CSIRO has found 'mustard' grown in resting soil can assist in the eradication of nematodes. This has been a problem in my garden for some time, what type of mustard can be grown? I notice your site says 'black mustard' can become a weed if left unchecked. A: I would think that you would source white mustard (Brassica alba) and black mustard (Brassica nigra) from agricultural suppliers or nursery seed suppliers. Many brassicas are already weeds in this country so if I was growing these crops as a nematicide, I would be digging them in before seedpods were formed.
	topic: pruning a tree to shape WA question: I have a very young hibiscus tileaceus, and would like to prune it into a tree, rather than a shrub looking plant. What is the best way to do this, and at what time of the year should i be pruning in Perth? A: You can start pruning now. Select either one or three strong vertical stems and remove all other stems. As these stems grow to become the tree trunks; rub any leaves, shoots or branches off the lower half of these trunks. Keep doing this as the trunks grow. A little and often is better than once a year in this case.
	topic: plants surviving sun AND shade WA question: The main garden bed in our back yard is North-facing, against a tall boundary fence. So the plants get full sun in summer and full shade in winter. I am looking for a bushy shrub approx 1-1,5m high, which will survive this condition. WE have tried many plants, but they tend to rot or slowly die off in the winter because they can't handle the lack of sun in the winter. Please help. The taller plants at the back are ok, as they're reaching high enough to get some sun but below them, at the next level, we need to find something to fill the gaps. A: Hebes, murraya, choisya, lophomyrtus, small pittosporums, small callistemons like ‘Little John’, small banksias, correas, derwentia and grasses like lomandra and dianella spring to mind. Pay attention to the drainage – it may be soggy soil that is killing the plants not a lack of sunlight.
	topic: Passionfruit NSW question: Why do flowers fall off a seemingly healthy passionfruit vine? I water it daily and feed it with cow manure about 3 times a year and have just given it some citrus food. I would appreciate your advice. I think your site is very interesting and has great topics and it is good that you can ask questions about gardening. A: Getting passionfruits to set fruit successfully is a tricky task. Some references say plenty of food, well-drained soil and lots of water is all you need. Irregular watering may have stressed the plant and caused it to drop its flowers. Fertilising a plant without watering it is enough to stress a plant. If the flower is not fertilised it will fall off – perhaps plant more flowering plants around to attract the bees.
	topic: Lemon tree not fruiting question: We inherited a lemon tree (either a Meyer or Eureka - it has large spikes) in a pot about 4 years ago and transplanted it into our garden. It has grown well, gets regularly fertilised and reasonably watered but apart from a few flowers and one lemon years ago has never had any more flowers or fruit. What are we doing wrong? A: Is this tree in full sun? It will not fruit well if it is in even part shade. Secondly buy some citrus fertiliser, follow the recommendations on the pack. Always water the fertiliser in well. Keep the water up to your lemon tree – they hate to go dry and lastly mulch your tree to lock the moisture in the soil.
	topic: growing banksias QLD question: I would like to grow some banksia plants in my native garden in Townsville, North Queensland. I was wondering what varieties would be easiest to grow and look the best? A: Alex George’s ‘Banksia Book’ would be a good place to look for tropical banksias. You could also look up your local Society for Growing Australian Plants – they would be able to help.
	topic: Passionfruit with no fruit NSW question: I have a prolific passionfruit vine that has been covered in flowers for the past 5 months and we have not had one passionfruit. I have heard that this is due to lack of bees, but a couple of metres away are a number of flowering plants such as alyssum, a daisy and various vegies. A: Have you had a lot of rain recently? Rain, gloomy weather etc puts a damper on bee populations. You could try a fertiliser marketed for fruit bearing plants (high in phosphorus) and see if that helps.
	topic: wood borer in poinciana tree QLD question: my poinciana's were failing and my nurseryman correctly diagnosed wood borer. he gave me a poison to apply with water to the roots. I did this twice, and three trees have recovered completely. but the fourth and sickest, though considerably better, still looks sick and one branch looks like its dying. how long should I keep up with the poison? A: I think I would be getting an arborist to look at the trees. I don’t like the idea of continuing to pour poisons on the soil. Sometimes it’s better to cut your losses and remove an affected tree. With one branch dying it sounds like it might be too far gone.
	topic: curl grubs in lawn want to turn lawn into no dig vege garden NSW question: New house, Have mowed lawn(30 years old lawn and VERy very thick thatch). BUT curl grubs are everywhere and quite deep down (1 metre) . If I plant fruit trees ( have 20 in pots ready to plant) or try to start no dig garden,how to stop grub attack Commercial lawn grub granules not recommended near food plants. A: There are a range of low toxicity products on the market for killing curl grubs. Some are pyrethroids – natural and synthetic – and some are made from other chemicals like imidacloprid. I have heard molasses and tea tree oil can be used to drench lawns and kill curl grubs. A biological control using entomopathogenic nematodes (this is called Integrated Pest Management or IPM) can kill curl grubs. Here is a list of IPM producers http://www.goodbugs.org.au/suppliers.htm
	topic: poisoning suckers VIC question: we have pine trees that are suckering everywhere 1/can we poison the suckers without killing the tree 2/if the trees have to die, are their any plants trees/shrubs that will grow under live pine trees, before we kill them. A: I have never heard of a pine tree suckering. Are you sure they are suckers and not seedlings? Try pulling one up and seeing if it is connected to a large horizontal root below the soil then you will know it is a sucker. If it comes out easily with its root intact it may well be a seedling. Maybe they are Athol pines which aren’t pines at all but a tamarix. Normally I would say if it was a big tree and little suckers, poisoning them wouldn’t hurt the ‘mother’ tree but it may not solve the problem. As a rule of thumb many types of succulents will grow reasonably well beneath pine trees if they receive enough sun.
	topic: citrus VIC question: My orange and mandarin trees are dropping their fruit and the fruit on the trees are splitting, this has never happened before, any ideas why ? A: These sound like stressed trees. It could be a lack of water or irregular water or not enough water for a long time and then too much water! Sorry not to be clearer! Citrus trees appreciate regular deep watering, regular fertilising and full sun.