As the ABC’s Gardening Australia celebrates its 30th anniversary, its host solves your gardening dilemmas

What are the best plants to ward off mozzies in the backyard? – slammy

When it comes to mosquitos in the garden, the first approach is to think prevention. Is there water pooling or sitting in unused containers or pot saucers in the side passage, or some old unused bucket? Remove these potential breeding grounds, and then you can think about planting a few different species of plants near any outdoor dining areas, or areas you are regularly in.

Plants with strong scent include: native mint species such as prostanthera; all the basils including perennial, bush and European; lavender; rosemary; catnip is very highly scented; lemongrass; citronella; the lemon scented gum; lemon scented tea tree and pelargoniums, which are more commonly known as geraniums. Rubbing their crushed leaves on your skin activates the oil and keeps the aroma field close. But remember: no specific plant is going to repel mosquitoes. It is more that the scent they give off distracts the mosquitos from smelling you and calling their friends over for a little blood-sucking festival.

We have a small 4 x 6m garden that gets no sun. The turf we laid has long since died bar a small triangle in the sunny south-west corner. It’s dusty as. We have two small boys, another on the way. A small trampoline in the centre. Fake grass would be easy and solve dust problems but I really dislike fake grass and feel it’s slowly creeping in everywhere. What can we grow there? – Sunryder

I hear your dilemma. Small children are like the sheepsfoot compactors you see at roadwork sites, crushing down the fill and compacting the ground for the finished concrete or asphalt surface. I experience this same problem in schools where a small space gets hammered every day by hundreds of children.

Don’t be fooled by getting a shade-loving grass because it’s the activity of feet that is creating the problem. Relative to surrounding trees and buildings, it’s important to work out what part of the garden gets good sun, because grass needs at least six hours a day so that it can keep regrowing. I see you have worked that out as being the sunny west corner. Perfect.

Synthetic grass gets extremely hot in the summer. With a trampoline as a focal point for the next few years I would be inclined to mulch the entire area around the trampoline, and run an optional raised garden edge to grow plants along the boundaries. Raise an edge in the area where the grass is still growing, too – you can use a narrow steel garden edge to, say, 150mm high – and make that area like a little blanket of turf that the boys can sit on for a picnic or lie on or do other activities on. By raising that ground like a little podium above the mulch, you can put in some free draining sandy soil, roll out new grass, and treat it as a special place.

Before putting in the mulch around the trampoline area, make sure you drop the soil level along the path or house side so the mulch sits below the path and doesn’t spill over every time the boys run over the join. Best of all, the mulch can be topped up cheaply and easily.

What’s the best way to combat those tiny little flies that take up residence in nursery-bought seedlings and potting mix, and plague my indoor plants? – Stephanie C

These are known as fungus gnats and I hear you when you say they are like a plague on your indoor plants. Generally their larvae feed on fungus that is growing on breaking-down potting mix. Fungus only grows on wet material, so start by letting it dry out as much as possible so it can break the life cycle of the gnat. Of course, be conscious not to starve the plant of water – just allow it to dry out, then water it, and don’t leave it damp.

Another option is to drench the soil with a horticultural oil mix, neem or pyrethrum solution. Alternatively, you can put a gravel or pebble mulch across the top of the pot. Make it about 20mm thick and it will create a barrier and isolate the insects from the fungus.

I’d love to grow my own vegetables but I live in an inner-city apartment without a balcony. Are there any edibles that can be easily grown indoors? – Steph H

As an inner-city apartment dweller you are part of an ever-growing tribe of enthusiastic gardeners who don’t necessarily have the space or the conditions to grow their own veggies. Probably the best start for you would be to sprout your own snow peas and mung bean: those salad extras that you can grow in a good bright place. Once you get success with these, then you could look at sprouting other salad greens and microgreens such as pak choi, celery, mustard leaves, silverbeet, beetroot and kale. You can really have a crack at most veggies and some herbs as a microgreen. Heres a link to a story that Jane Edmanson did on growing these at home.

What’s the biggest faux pas, mistake or blooper you’ve ever made on the set of Gardening Australia? – Guardian staff

Thanks for the question and thanks for rattling the garden shovel whenever you can. We were filming with an orchid lover, the state president of the orchid society, the king of orchid royalty. So we are walking around and he shows me this most exquisite orchid – a flower like no other I have seen before – and I decide to take a photo. The producer is like, “Cut! Cut! Cut! What are you doing?!” Oops! I was so in the moment, I forgot we were filming, and thought I was just having a chat with a mate! And that’s what gardeners are like at the best of times – lost in the moment.

How many times have you told people your job and they mishear and think you work for us? – Guardian staff

Funnily enough, I have been asked this a few times – not face-to-face, as you can imagine, but over the phone. It wasn’t when I was ringing a nursery or landscape supplies or landcare group; it was more when I have called up a non-aligned organisation – when you get sent to a call centre and the people hear the harmony between “Guardian” and “Gardening”. We must be brothers from another mother, so to speak!

In Melbourne we have an old lemon tree that’s been blighted by citrus gall wasp. I have pruned off affected branches for years but it’s just getting worse. I think it’s on its last legs – is there anything I can do to help? – Melmot65

Fellow citrus lover: if I was the garden dictator of the world, every citizen would have a citrus tree – at least one by decree and one for all their family members, too.

I have also had citrus gall on the family lemon here in Melbourne. I came out and cut it back so hard to remove it all completely and the tree was looking like an upside down three-legged stool. Then I forked the ground around the drip line of where the canopy used to reach, and then I did what is called a “lifesaver’s collar”: I put out some rock minerals onto the soil and then watered them in with a seaweed solution. Then I put a 200mm layer of lucerne mulch, sprinkled half a bag of cow manure over this, and watered it in with a watering can of fish emulsion fertiliser.

Then add another layer of lucerne mulch and this time put half a bag of chicken manure, or pelletised chicken manure – whatever you have. Water this in with liquid fertiliser – either fish or seaweed. You can then add some compost to this layer and cover with straw. Be sure this tapers down and is clear of the turn. This will all break down slowly and feed the tree over the season ahead.

How do I get rid of stink beetles on my citrus without also murdering bees and other insects? – Rumtytum

One method that I have used and have seen others use is to have an old second vacuum cleaner and vacuum them up off the leaves. One with a good extension arm means you can reach to the top of taller shrubs and trees such as your average citrus, which you never want much higher than 2–3m for easy access to fruit. Make sure that when you are doing anything where stink bugs are concerned you always wear your sunglasses or safety goggles in case they spurt their protective juices your way because they can get you in the eyes.

I have a tomato plant given to me by my father. It’s an heirloom variety called moneymaker, supposed to be large tomatoes. I water it twice a day as the pot isn’t much bigger than a bucket and have given it a feed of sheep manure soaked water every few days, but even though it’s growing really tall and has over 20 odd tomatoes fruiting, none are bigger than than a large cherry tomato, and some leaves are turning brown and dying. Do you have any advice? – phreddy

It’s hard to tell without being there and it could be a big range of issues. Tomatoes are fussy and wilts are common. Watering could be a bit much. Ease up. From some recent experience, this suggests that your plant could have a rust disease that slowly works its way up from the ground, browning the leaves that then dry out and die. Because the plant is stressed, the fruit are not getting the food you are providing it, hence their small size. The solution to this is to mix up a sulphur solution and spray onto the plant once a week, outside of the heat of the day. You should see results through renewed growth of the plant and the fruit beginning to expand.

I live on a rural property near Maleny in south-east Queensland, where we grow as many of our fruit and veggies as possible. I am struggling to grow healthy plants in our increasingly extreme summers, despite taking many measures (eg shaded beds, drip irrigation, attention to soil and mulch). Do you have any tips? – ardribrianboru

I hear you, but don’t despair! What we are looking at here is a change of direction as far as species and seasonal expectation are concerned. Living in the subtropics means the conditions make it much more challenging for you to have success with classic English veg. Don’t be afraid to experiment with different species.

Aibeka and malabar spinach are two examples of greens that grow really well. Give things like wall rocket (diplotaxis tenuifolia) a go. Of course there are warrigal greens, amaranth, cocoyam (xanthosoma sagittifolium), society garlic, cassava to name a few. Try adjusting your sowing and growing times to the more tropical seasons and expect shorter windows for your harvest. That’s not a bad thing. It’s more a case of getting to know those sweet spots and making the most of them.

And of course, check out local community gardens to see and talk to locals about what they are growing successfully. They are in your hood and know the nuances and pitfalls you are facing. Here’s a great story Jerry Coleby-Williams did with plenty of tips to help you get through your hot summers. Grow on with it.

Gardening Australia’s 30th Birthday Special airs Friday 15 February at 7.30pm on ABC TV