Fiona Eadie is head gardener at Larnach Castle in Dunedin and Tony Murrell is principal designer at Auckland landscape design firm Murrell Gardens. On today's The Weekend, they answer listener questions from across the motu.
On the summer so far, Eadie said it had been erratic. "You don't live in Dunedin for the weather. We go from 30degC to 10C and that can be in one day. So we are ... moderately dry, but probably not as dry as some places."
She added that her team at Larnach Castle did hardly any watering, "because we plant plants that are suited to the environment".
Murrell said he hoped garden centres would provide advice on planting for local conditions and a range of plants suitable for local soils.
"I went to a house the other day in Ohakune and at the front of the house they were going to plant a range of plants that would have fried in the first morning sun."
Instead, Murrell suggested Cornus alba 'Sibirica'. "It'll take the morning heat. And in the winter time, you'll get these amazing swords of red that you can use for a cut arrangement inside the house. And it's just coming up with different kind of options and I wonder if everybody has that advice available in garden retailers around the country."
Eadie described water as "the new gold".
"Look at Wellington. You look at Auckland. In some ways the whole New Zealand ... farming is demanding a lot of water, so there is less water available for our urban environments.
"We do need to seriously start selecting plants that are more suited to our conditions. Save your water for your veggie gardens, for your fruit trees. For those that are [producing food]. Select the appropriate plants for your conditions."
Murrell added that irrigation was one of the biggest challenges he had faced when installing gardens recently. So many sites require irrigation for the first couple of seasons to get plants established, because often we're using larger grades of plants, whereas some designers use much, much smaller grades and lots more plants, which works incredibly well."
He viewed irrigation systems as a "temporary insurance policy", using drift and monitored irrigation.
"It's not vast amounts of water. Also [when] choosing where some people do still require lawn, making sure that the lawn species ... will cope with the conditions. So it requires more work, more research, but it's a lot of fun and ... I'm still learning."
Q: Are there any flowers that rabbits will 100 percent not eat? - Alice, Queenstown
Eadie: "Rabbits eat anything.... At [now closed] Oratia Native Plant Nursery, the rabbits would come in and they would do a block. It was like, 'What will we eat today?' And they didn't care if it was carmichaelia - native brooms - they would just take them down to ground level. They would go away, they might do that for a couple of nights and then, 'Oh, we're a bit sick of those. I'll just go and do these.'
"They don't care whether it's got woody stem or it's a bit hard to chew - rabbits kill them. The best way to do it is to rabbit fence your property. I've got a property in Central Otago outside of Alexandria. We have rabbit proofed it - a one-off cost."
One form of rabbit control that Fiona Eadie recommends is Plantskydd. "You mix it up and it looks like you are mixing blood. You spray it on your plants... they absorb it. You can irrigate or if it rains it will wash off. It will protect your plants for a good three months."
Q: I'm struggling to keep potted plants alive in my sunny northwest-facing deck - Auckland
Murrell: "I've turned a lot of pots into self-watering pots, where you put a flange in the bottom, creating a reservoir at the base of the pot using a combination of either coconut fibre or pearlite. Any excess water then flows out from that reservoir and then your normal mix [on top].
"I like to over-plant pots and even if there aren't many plants in a pot I like to put down ... a layer of grit or fine gravel to maintain that water. Having your pots as a collection, as a "cuddle", will certainly keep humidity and ... more water. Sitting [pot plants] in saucers is not the best idea.
"Find a range of plants that can cope with the heat and the humidity. Whilst we all love geraniums and pelargoniums, they will suffer a little bit with mildew. But I reckon if you water at the base and you rotate those plants at least weekly, you'll get a wonderful show."
Eadie suggests packing the soil tightly in pots. "It slows the growth rate down and it means that you need to water them less often."
She also prefers shorter, lower pot sizes. "If you want to have a tall pot, you must plant a dry-loving plant because all the water is sitting at the bottom section of that [pot]. When water comes ... there's no gravity pulling it down any further. The water just sits in the bottom layer. You will get a day or so out of [the watering], but that's probably it."
Q: How do I control pear slug - the larvae of the mayfly? - Geoff, Wellington
Eadie: "Fix up the environment that the pear is in. There's something wrong. Plants can defend themselves from pests and diseases better than animals. A sick plant means, 'Can you please make my environment a little bit more suitable for me?' Is the ground too wet? Is it mulched? Is there the organic matter in the soil, am I getting too much wind? Am I not getting enough wind? A sick plant means the plant is trying to tell you, 'You fix my environment up and hey I I can look after myself, I can fight off the pest.' "
Murrell: "After you've taken care of all of those things, [look at] the soil, look at the conditions where the tree is growing, looking at the optimal range of conditions that the plant would like. You may have to simply take that tree out and try something else."
Q: We planted a passion fruit in October, dug a good hole, added compost and sheep pellets. Many of the leaves have fallen off. Is this normal? - Rayma, West Auckland
Murrell: "You want to give your passionfruit vine a good, healthy start. I always add compost to the top [soil around the plant], so nature can take it down naturally. It's all about plant establishment for the first couple of seasons and making sure that you've got a climbing system or frame for the plant to spread out and get established. And once it's done that, and it's showing signs of high health, then later you'll add to the top of the soil during the growing season [from] early spring ... a few sheep pellets, maybe a little bit of tomato food ... or, as many gardeners do, a compost tea, or a worm tea. But really, those plants are resilient and tough and don't require a huge amount apart from a jolly good watering from time to time."
Q: What can I plant next to a fence to fill a hole for privacy? There's not much space between us and the neighbours so it needs to be a couple of metres tall but not grow over the fence or get too high or out of control. - Paul
Murrell recommends planting an abutilon, or Chinese lantern shrub. "It's fast to grow. The flowers are amazing. You can trim it and keep it to the size that you want, but it will actually balance out the way that it wants to be. It'll cope with your soils and the range of colours is extraordinary."
For a narrow space, Eadie suggests putting a couple of wires along the fence and planting a clematis. "Or a tecomanthe and you can just keep it trimmed. It covers [the space] very quickly and it flowers."
Q: I have a large puka tree [Meryta sinclairii]. Some branches and leaves are turning yellow and dropping off. Should I cut off these branches? - Ruth, Lower Hutt
Murrell: "I quite like the puka tree [but] I've had mixed success with those. ... Because I tend to just leave puka alone, if it's dropping a lot of leaf it could have phytophthora."
Eadie: "100 percent agree... which means that it's in the soil. She's losing one branch now - she'll lose another branch. And probably with the weather ... over the last 12 months as the soil's got very wet and then it's got very dry, and then wet again, so phytophthora has taken off. And probably if she's losing a branch at a time, I'm going to say very sorry, but it's going to die. Let's chop it down."
Murrell added that after getting rid of the puka it would be a good opportunity to improve the soil and prepare the ground for a new tree.
Q: What's a way to prevent or counteract mildew in the garden? We have a lot of shade, but the mildew strikes everywhere, even in sunny spots.
Eadie: "I'm going to come back to that basic premise: with plants that are sick, there is something wrong with their environment. You need to either select appropriate species or look at your soil and all those things. The whole thing about gardening is you do need to know your plants and you must know your environment."
Murrell suggests a visit to Pukekura Park in New Plymouth or the Auckland Botanic Gardens, both of which have a range of shade-loving plants.
Q: Are there any other solutions for a deluge of white fly in my veggie garden? I'm using Neem spray on the underside of the leaves.
Eadie: "Again, if the environment is right, plants can defend themselves against white fly. It might be fluctuations in the moisture level. We have got fluctuating heat levels, which are going to cause some plants to become stressed if they're not used to it."
Murrell: "Let's see what the white fly attacks and takes to the ground, and let's see the plants that do actually survive this attack. And it's those resilient plants that might have a higher Brix value, higher nutrient density that [can] resist the attack of the white fly. I think this is a really nice opportunity for you to do a little experiment at your place. What survives?"
Q: How do I get rid of thick weeds and vines around a kauri tree?
Eadie: "Kauri are shallow rooters - if you put a huge pile of mulch on top, you've got a likelihood of killing it. Go through with the weed eater to start with."
Q: I live in a coastal environment. Will I be able to grow gardenias? - Rosie, Hawke's Bay
Murrell: "I think in a sheltered spot, yes. You could try to start off with something small like Gardenia augusta 'Radicans' or even Gardenia jasminoides 'Veitchii'. Quite nice to try a couple in pots as well. Try the 'Professor Pucci', which gets a little bit bigger. They do cope with coastal conditions, but they want some protection and maybe plant some false valerian (Centranthus ruber 'Red Valerian) - that would be quite a nice balance to give it some protection and it likes the coast."