How climate change impacts what fruit and vegetables we can grow in our gardens
Climate change and global warming could mean more New Zealand gardeners can grow the tropical fruits flourishing in Hugh Roses Northland gardens. The chairman of the Tropical Fruit Growers of New Zealand boasts the largest collection of banana varieties in the country, happily fruiting on his 24ha Maungatapere block. A pineapple plot is also being formed, while various other tropical and subtropical foods are plotted around the garden: Rainbow pawpaw, ice-cream bean, sugarcane, papaya, ginger and coffee. Should climate change mean hotter temperatures and more carbon dioxide in the atmosphere, both Rose and his banana plants would welcome it, he said. READ MORE: * Climate change: pros and cons for gardeners * More pests, new diseases, starving pollinators: gardening in a changing climate * Climate Lessons: How climate change affects New Zealand wine Bananas have been growing in New Zealand since 1890 and can now grow as far south as Invercargill, as long as they are watered, fed with compost, pruned and protected from frosts, Rose said. More gardeners should also try their hands at pineapples, sugarcane and mangoes grown under shelter, he said. Niwa climate scientist Gregor Macara agreed climate change will result in higher temperatures, which will both increase the growing season and enable faster crop development. While New Zealands weather will always remain variable, climate change will shift the average weather conditions expected for a given time of year, he explained. But climate change is not all good for the garden, as it also increases the number and severity of both floods and drought , Macara said. While there is not a lot gardeners can do about floods, other than installing raised garden beds, in times of drought or prolonged dry periods, watering and irrigation is critical, he said. In some areas, local councils ban the use of hoses ; therefore, gardeners may consider means of water harvesting and storage - such as tanks that collect rainwater from the roof and using buckets to collect household grey water. Auckland home gardener Gillian Shine has had to cull how many thirsty plants" she grows in her veggie garden, as climate change makes conditions hotter and drier. Gillian and husband Greg have gardened their 6.5ha property, in Waitakeres Bethells Beach , for 38 years and have noticed the temperatures getting warmer. There will always be seasonal variations, but the trend is definitely longer, hotter and drier summers, she said. We used to get just three or four days over 28 degrees, and it was constantly over 30 degrees for two weeks [in November 2020], Shine said. We used to get frosts right through to October ... now they stop in July. While the property uses a spring as its water source, Shine said the time it takes to water crops has meant she has had to cut down on how many potatoes, pumpkins and rows of corn she now plants each spring. "I have now got just one small crop of each. But while these crops have been cut back, other veggies are thriving in the conditions when compared with the 1980s. I couldnt grow sweet basil, or capsicums or chilli, but now Im getting really good crops of them. The tomatoes are lasting so much longer Im still picking them in late April when normally I would finish in February. Ruud Kleinpaste, also known as The Bugman, said pest insects and diseases were guaranteed to be more of a problem with climate change . Insects are ectotherms they have no interior heating and take all their heat from the environment. The warmer it is, the quicker they can fly and the more they can reproduce. Thrips, mites, leafminers, caterpillars, scales, mealybugs, ants, even migratory locusts would welcome higher temperatures, especially in the winter as it allows a much better survival rate during the cool season, Kleinpaste said. Gardeners will have to adapt to these threats, he said. For example, Kleinpastes garden in Christchurch's Port Hills has a problem with tomato/potato psyllid . To stop them becoming a nuisance on his tomatoes, he has stopped growing potatoes and vigorously pulls out any solanum weeds, such as nightshades, growing in winter. Climate disruption the increase of droughts and floods will also be more difficult for gardeners to deal with, Kleinpaste said. Water harvesting and storage is key to making the most of rain when it does fall, and using mulch and compost will help retain water when it is dry, he said. But Kleinpaste does see some positives with rising temperatures: Avocados and citrus can successfully grow on the Port Hills, as long as they are shaded from the winds and the frosts. Tropical fruits such as lychees are now viable to grow in Northland, although it might take another 200 years of climate change before they are viable in Christchurch, he said. Climate change has already changed what foods can grow in New Zealand, as shown by a trial of peanuts grown in Northland for Nelson company Pics Peanut Butter , said Manaaki Whenua Landcare Research senior scientist Dr Nicholas Cradock-Henry. Pic's is growing peanuts in Northland that in itself would've been probably regarded 10 years ago as either highly unlikely or totally unfeasible. Climate change means droughts will become more of a problem, especially in east coast areas such as Northland, Gisborne, Hawkes Bay and Canterbury, Cradock-Henry said. In a recent study, Growing Kai Under Increasing Dry , he found droughts cost New Zealanders about $720 million between 2007 and 2017 six times the figure for flood damage. Severe losses of up to 54 per cent in sheep and beef farm profits are expected by 2100. While Cradock-Henry has studied commercial producers, he said there were lessons to be learned for home gardeners too. Water harvesting such as rainwater tanks or dams is key to getting through periods of drought, especially when municipal water supplies are under stress , he said. Crop diversity is important for buffering ups and downs which for home gardeners means growing several types of tomatoes, as well as other crops such as beans and lettuce, Cradock-Henry said. Small gardens are the perfect opportunity to experiment with what works, he said. Cradock-Henry said his studies found New Zealand's food distribution system was very vulnerable to disruption by natural disasters, as demonstrated when flood damage caused the Ashburton Bridge to close in June, cutting off supplies to towns further south. Having a home veggie garden, and preserving some foods, helps protect families against these emergencies, he said. It also helps to cut the carbon dioxide emissions which cause climate change, by reducing the number of trips people take to go to the supermarket. Growing your own vegetables is probably not going to make a big difference, but I think its intrinsically valuable. Hugh Rose agreed, saying the likes of bananas were valuable not only for their fruit, but their flowers - which can also be eaten, their leaves which are used in cooking, the stems which can be eaten by cattle, and the offshoots, or pups, which are in high demand for planting. Bananas also feed on nitrates and phosphates, which New Zealand dairy farmers are under scrutiny for discharging, he said. And growing your own will help reduce some of the 72 million kilograms of bananas imported each year for eating.