Winter gardening with Lynda Hallinan

There is plenty to do in the garden over winter, gardening expert Lynda Hallinan says. She joined Anna Thomas to answer listeners’ gardening questions.

Is it too late to sow a winter crop in Christchurch?

“It depends on the soil. If you've got raised beds, your soil will be warmer anyway. So, you can still grow things like kale and bok choy, Chinese vegetables - they're really just fast-growing brassicas that suit Asian cuisine.

“All those things are real quick and you can put them in at this time of the year. They're all cold-hardy, so they don’t mind a frost.

“You can sow broad beans, peas and snow peas, all those sorts of things.

“What you don't want to do is plant cabbages, broccoli, and cauliflower, because they will take until spring now to actually do anything.”

She also recommends putting in silverbeet and spinach.

“They can go in now and they go right through winter and you just keep picking them, you don't have to have the whole plant. So, they're really good value and fast.”

I have a large quantity of native timber sawdust untreated wood and it's been sitting outside for three to four months. Can I use it on the veggie and/or flower garden?

“There's a big controversy about whether you should use mulch, fresh or not.  Whether you should set it aside for a year and let it break down so it doesn't rob your soil of nitrogen.

“But in all my years of gardening, I have used whatever mulch I can get my hands on and nothing has ever died from fresh mulch; it'll die from being too wet or too dry, but not from fresh mulch.

“And if you're using small quantities, it doesn't matter at all, just chuck in some garden fertilizer at the same time, some coffee grounds or anything green like fresh compost,”

Mulch is just as beneficial in winter, she says.

“If you're mulching any soil that hasn't got anything growing in it, it will stop the weeds from growing because they won't germinate through the mulch and be it'll stop all that goodness in your soil from leaching off in heavy rain, and we've seen so much heavy rain.

"Erosion from gardens is a big thing. If you've got a vegetable garden it'll wash all of your good soil and all the goodness in it out. So, mulching is a great way just to kind of put a winter blanket on it.”

What is the best way to deal with army worm? Will neem oil work?

“When you've got a worm that's called an army worm, you know you're in for a battle, right? It's like this camouflaged caterpillar. But it is a nightmare and it's new to New Zealand.

“So, the army worm and the guava moth are two bugs that have breached our biosecurity in recent years, the guava moth’s been around for over a decade now and it's pretty much just destroying everybody's feijoas in the northern part of the country.

“The army worm’s new I've only had it for the first time in my garden this year.

“It is hard to combat, it is huge, and it eats so much in one night. So normally people would be aware of say, the white cabbage butterfly caterpillar, which will munch holes in your cabbages and then your brassicas, this thing will eat the whole plant right down to the ground. My parsley disappeared pretty much overnight.

“And so it's really tricky. I mean, you can use derris dust. That's like a caterpillar specific insecticide and I actually went and bought them this year for the first time. I don't really recommend using chemicals and that's the only thing I've used because it's either the army worm or us - like that's how bad the bug is.

“They will laugh in the face of neem oil, you're gonna have to use a caterpillar-specific spray, or derris dust or just go pick them off because they're huge. You can see them easily, but usually you don't know you've got them until they've eaten everything.”

How to prevent rust in garlic?

“It's another insurmountable problem. Unfortunately, there's no real solution to allium rust.

“The only thing you can do is plant your garlic somewhere else and plant early, so it should be in the ground by now. Normally we would say plant garlic on the shortest day in winter and harvest on the longest.

“But if you leave planting garlic until June-July, in areas where allium rust is prevalent, so that's anywhere with humid weather, then what happens is that the plants actually succumb to rust well before they’re finished bulbing-up and so it just stops them from growing and you get a really lousy crop.”

Can I put fresh horse manure and when planting trees or does it need to be left a year to rot or decompose?

“You can use it fresh on trees and shrubs, what I wouldn't do is stick it straight in your vegetable garden, because as it decomposes, it gets quite hot and so it will literally shrivel the roots of small plants but on trees and shrubs will be fine.

“You can mix it with your fresh mulch, some grass clippings, stuff like that, just put it on top of the soil and leave it kind of break down as it goes.”

I have three standard, Margaret Merril roses, 18 years old, and they're dying from the tips downwards. Normally I wouldn't prune until late July, but I'm tempted to prune hard now. Is it too early?

“They might just be losing vigour. Eighteen years is pretty good going for standard roses because they're grafted, so they look like a stick with like a lollipop on the top.

"And so you have to continually kind of prune them to keep that top knot of growth growing actively.

“If they've slowed their growth, maybe there's more shade in the garden over that 18 years than when they started, they will slowly start to lose vigour.

“I would prune it back if it's dying back because you don't want the die back to continue. And you might want to give it a clean-up spray with some copper to keep it healthy and then make sure you feed the bejesus out of it in Spring.

Kathleen says: After nearly 30 years in my current home kikuyu grass has dived under the small concrete barrier. I'm finding it very hard to dissuade it from staying given I don't like using sprays any ideas?

“I would spray it. There's lots of organic sprays that are just made from fatty acids and plant oils.

“You can use those and they're easily available at garden centres, but you'll need to go back quite a long way because it will come straight back in to fill up the gap that you've left.”

What would type of veggie pod would you recommend?

“I think those veggie pods are great just try any that you like the look of.

They’re self-watering, they've got a lid on them to stop the worms, they've got bug control. If you're starting out, I would highly recommend them. They're expensive, that's the only factor, but just go and pick one that you like the look of and go for it.”