Garden Q&A: Lynda Hallinan answers more of your gardening questions

From non-flowering kōwhai to kitten poo, to tickling your seedlings – Lynda Hallinan answers more of our listeners' gardening questions.

I have an avocado growing indoors, I'd like to grow it outdoors but the older leaves have brown tips…?

If all of the leaves were brown then yes, it would be dead.

You've got to remember that things like avocados are evergreen, but even though they're evergreen doesn't mean they hold on to their leaves their entire life.

It sort of depends on why they went brown, so if it's indoors it's not likely to be cold, it's more likely to be too much water or not enough.

What I would suggest is get it out into proper conditions this year and you'll be fine.

Kōwhai trees not flowering?

The thing with kōwhai … there's quite a lot of different varieties and some are definitely more floriferous than others.

There's no easy solution to make kōwhai more floriferous, they don't flower while they're young.

Sophora microphylla - which is kind of a tangled, wiry-looking specimen - they don't tend to flower well until they've grown out of that, that's a juvenile phase. It could be 15 to 20 years, I hate to tell you, before it gets going.

The other thing with them is that you don't want to be feeding them, so don't give them a whole lot of nitrogen fertiliser ... you won't get any extra flowers.

In Auckland, the actual variety that is most native to Auckland is called sophora [fulvida] … so look for that at garden centres.

There's one called sophora godleyi - Godley's Mantle - and that is stunning but you'll have to get it by mail order.

The native kererū, they're crazy for the buds, the flower buds on kōwhai, so if you've got an old tree and it's doing really well but for some reason it's got no flowers on it this season, it could be a big fat wood pigeon has just come along and stolen all the buds.

Raspberry plants showing no signs of life, flooded by seawater during a cyclone in February … some have obviously rotted but others are firm in the ground?

My raspberries are still definitely dormant, there's no signs of any growth on them yet, so just be a little more patient, maybe give them another month.

If they have been flooded by saltwater they won't like that much ... just wait a little bit longer I would say.

Caterpillar on Lilly pilly?

They can get munched quite badly by caterpillars … you can spray them with a quite a good low-tox spray called Kiwicare Organic Caterpillar Biocontrol and this is great because it doesn't affect anything but caterpillars.

Spray the bejeezus out of it, and you'll need to reapply it after rain but hopefully, you can really get on top of your caterpillars.

Avocado plant grown from seed from the supermarket … do these tend to be fertile?

The problem is that you will get a seedling which won't necessarily be the same as its parent, so you may be waiting for 15, 20 years again to get it to fruit. 

It may never fruit well, it will eventually fruit, but what you could do is plant it in the garden somewhere and then go along to the tree crops association and join up and go to a grafting workshop and get a little bit of budwood and have a go at grafting a proper fruiting variety on to your rootstock.

Then you'll get fruit in ... four or five years.

Frost-prone area of Central Otago, in a former riverbed with young trees - how do we nourish them?

I actually have quite a strong philosophy on tree planting … treat 'em mean and keep 'em keen.

If you plant a tree and then you cosset it a lot … get out there and feed it and water it all the time and fuss over it, what tends to happen is they stay much more shallow rooting, and in an area like Central Otago where you have vast extremes of weather, what you want your tree to do is get in the ground … so its roots go as deep as possible to really get into that lower substrate and get the water.

My advice would be this: plant your tree and then don't water it, which is horrifying because one of two things will happen: it will grow or it will die.

Give it heaps and heaps of mulch instead … like a doughnut, so that it's not actually touching the trunk.

Try to find species that actually do really well in that area anyway.

Which veggies should I plant?

Same advice I give everyone, grow what you like to eat. Be honest with yourself - if you don't like kale, don't plant kale.

Go through the section of your grocery bills where you're buying things every year, and if you're buying carrots, grow carrots, if you're buying potatoes grow potatoes.

Just wait until Labour weekend, if you wait until then the soil warms up just enough that everything will grow well and you don't need to worry.

It's still a little early, still a little wintry out there today.

Growing fuchsia

There are several different native fuchsia - fuchsia percumbens, which is a little groundcover, it's quite a fun little plant to tuck in amongst … say, some railway sleepers.

It has quite funny little flowers, and they're tiny, so if you think you're gonna get something like an exotic fuchsia you're wrong.

Otherwise, you can grow the native tree fuchsia, same thing, it's a little bit scrappy. I wouldn't say it's a real star plant for a garden, but it's certainly something you can pop in to sort of a bush area.

Sweet peas

Definitely, you can sow your sweet peas now, it's pretty easy, all you need to do is buy a packet of seeds and poke little holes in the ground and it's done.

Feijoas in Queenstown

They should grow in Queenstown … the trick with that would be just to check with your local garden centre as to the varieties they sell. There's a whole lot of feijoas that have been bred in the South Island conditions and they will be available in garden centres now.

The ones that I like best are kaiteri and kākāriki - they've both got huge fruit early in the season so they're not so impacted by frost.

Guava moth on fruit trees

Guava moth is a new bug that's really only impacting the top half of the North Island, so from about the Bay of Plenty, north.

It gets into fruit crops and it just destroys them, its a real problem on citrus and on feijoas and it lives its whole life inside the fruit so you can't even spray it once it's in there basically.

What you can do to try and prevent it … use a caterpillar-specific spray … or what's happening now in Northland is the growers are using moth traps.

That's very broad-spectrum, which is another way of saying it will kill every moth that flies towards it, but it seems to be having some effectiveness. If you're having a real major problem you could try getting one of those.

Lilacs for Auckland?

Oh dear. No … I've got a couple in my garden - they do grow, you'll get a nice bush, but you won't get any flower buds.

They need a lot of winter chill to kind of initiate that bud development.

Hazelnuts - do they need another tree for pollination?

Hazels are really lovely, they make a beautiful hedge. They can take four to six years to actually produce fruit, and they're really interesting because what you need is a pollinator plant.

You need a male plant that has the catkins that drop the pollen, and then you have the female or producing plant that has these teeny teeny teeny tiny - almost impossible to see - pink flowers.

They need to be flowering at the same time.

If you've got a fruiting one you might have whiteheart or Barcelona or Tonda di Giffoni ... for a pollinator, which could be what you're missing, you'll want Alexandra or Merveille de Bollwiller.

If you have one nut you must have a female ... the female ones do have [some] pollen as well, but it's better to have another variety.

General advice for right now

It's still really wet!

Don't go planting until your soil dries out, in fact, it's a good piece of advice generally that if weeds are sprouting in your garden - like if you go into your vegetable garden and it's filled with weeds - then yes it's time to plant.

Cold soil isn't as bad as cold, wet soil ... what you can do if you want to get a jump start on the season for growing veggies … put down some black plastic or a cloche and try and dry it out a little bit between now and maybe another month.

Citrus looking a bit sick on the tops

What happens with citrus is they are subtropical, and so if they do get a hint of frost on the top - even a light frost - they might take a wee while for those leaves to drop off.

The tips will die back and then you can cut those off - but once again, just wait a little longer. I can guarantee you that we haven't seen the last of winter even though it's technically spring.

We usually get some really cold weather at this time of the year and you don't need one really hard frost when you've just pruned back your citrus and you've got new growth coming - it'll just wipe that out.

Caterpillars and slugs on herbs

It must just be very wet … herb gardens generally should be quite dry because that's when you get the best flavour.

Slugs and caterpillars, they like a bit of moisture, they don't do so well in the dry, so maybe look at putting some herbs in a different spot in your garden.

Not too much rocks around - like a rock-edged herb garden, like I have - is a disaster because all the slugs and snails live in the rocks then come out at night and eat everything.

Even maybe look at putting some in pots.

Parsley and mint

You shouldn't have a problem with parsley and mint being destroyed.

Mint dies down in winter, there are some varieties that will stay kind of semi-evergreen but it's coming back now. Give it another couple of weeks and you'll be amazed.

If it is looking a bit rough and woody and bare, just chop it right back down to the ground because it actually grows from underground stems really lush and lovely.

The neighbour's kittens are pooping in our garden!

There's nothing you can do, I mean they've got to go somewhere don't they, would you rather they do it in your house?

One thing I did one year was when I was pruning my roses, I jammed all my rose prunings in everywhere … the problem was they all struck so I had all these roses growing in places I didn't want them.

Why are the regular trees you buy grafted?

Say you want to grow a Granny Smith apple, what you actually want to do is make sure every Granny Smith apple is actually a Granny Smith apple … so rather than sowing seeds and having a little bit of variation, what the nurserymen do is they clone a little piece of the Granny Smith onto a rootstock.

The rootstocks can be chosen because they're vigorous, they might grow twice as fast … they might be disease resistant, they might be better at dealing with clay soil for example, or they may be dwarf.

Sometimes the grafts can fail and sometimes you get a lot of … suckers, which is bits coming off the rootstock - if you've got a vigorous rootstock, just because you've cut its head off doesn't mean it doesn't want to still propagate.

Fruiting tamarillos

You could feed them if you wanted to with a … flowering fruit fertiliser that's high in potash.

They should fruit pretty well.

They do get targeted by the tomato-potato psyllid, and actually, tamarillos are a bit of a nightmare now because they're the overwintering place for these bugs.

Getting dahlias into a crowded flower garden

Dahlias can go in quite deep.

I've got a garden where I've got the same problem, it's a picking garden and it's got lots of early cheer in full flower now, but I wanted some dahlias as well and so I just kind of shoved holes and jammed them in between the other bulbs.

You could lift the whole lot of the bulbs, and then shove your dahlia tubers in [underneath] and then put the bulbs back down and the dahlias will grow up through them.

Port Wine Magnolia looking yellow?

They're not frost-tender as such, they don't lose their leaves but they do turn yellow when they're cold, so they obviously don't like the cold.

I think what that is ... it just means in winter they don't uptake the nutrients they need to stay green. If they're still looking really yellow in about a month or so, just go to the garden centre and get some yellow leaf remedy, which is magnesium, or you can get some Epsom salts.

Once again, don't do it yet because it's still too wet and it will just leech away.

Growing strawberries in Christchurch

The trick is heaps of food, the more food you give them and the warmer the soil - you want to be north-facing.

Plenty of water at this time of the year when they're growing and flowering, then ease up a bit when the fruit starts to form.

My main advice would be to plant a variety called camarosa … it's just a really good do-er across New Zealand.

How to make seedlings stronger

When you think about how seeds germinate in the wild … they get rained on, they get a bit of sun, they get a bit of cold, they get a lot of breeze, so they toughen up naturally by having those elements.

When you grow them indoors you cosset them: you keep them really warm … so what you can do is tickle them.

I know it sounds nuts but just run your hand over the seedlings a couple of times a day … it just strengthens them up a bit.

The other thing is never sit them in a tray of water, so only ever kind of lightly mist them with water because otherwise, they get something called damping off.

They kind of rot at stem height, so they're all looking really good and then all of a sudden they wilt and flop.

Even if you've got them on the windowsill, open the window, and then they get a few changes in temperature throughout the day.

Treat 'em mean, keep 'em keen.

Pea straw sprouting lots of peas

They'll be very long and stringy … you might get free peas, I've had free peas in my strawberry beds.

On the whole, if you were to just rake around with the straw they'll come out of the ground, because often they're nowhere near the soil ... they've actually germinated in mid-air but there's enough moisture in the mulch.

Do peonies grow in Auckland?

You can buy peonies in Auckland, and you can plant peonies in Auckland - I've got them in my own garden - but they will not flower in Auckland.

Some people will have one or two … they really need a bit of winter chill and that's where they do really well in places like Marlborough.