Walnuts
Tips for a better harvest
If you want to provide for your children, the old saying goes, plant fruit trees; and if you want to provide for your grandchildren, plant nuts. But these days you may not have to wait too long to enjoy your walnut crop. Grafted trees start bearing within three to five years, and seedlings 10 to 15 years.
The Marlborough property of walnut and hazelnut growers Jenny and Malcolm Horwell, owners of Uncle Joe’s, already had two century-old walnut trees on it when they bought it.
“Those two trees are what got us into Uncle Joe’s as a business,” says Jenny. “The children used to pick up the walnuts and sell them to the Nelson person we bought the nut processing business from. Uncle Joe was his Blenheim uncle, who he used to stay with when he was a young man. They used to listen to the rugby, crack walnuts and throw the shells into the fire, so he named the business after him. Uncle Joe’s family still lives in Blenheim.”
There are many old walnut trees planted around Marlborough by early settlers, but there are many grafted varieties as well, says Jenny. Most commercial walnut orchards grow two main cultivars: ‘Meyric’ and ‘Rex’ – two that were recommended by the New Zealand Tree Crops Association following trials they set up in the mid 1980s. Nelson Hubber, chairman of the New Zealand Walnut Industry Group, gives them the thumbs up for the garden too.
“The smallest tree is ‘Rex’, a New Zealand variety. It will produce early and is blight-resistant, and although the nuts are small, I think it'd be my choice for the home garden,” he says. “‘Meyric’ has a larger, sweeter nut with a wider appeal, but the tree is big and it’s subject to blight. ‘Wilson’s Wonder’ is often sold in garden centres and it creates excitement because the nuts are very large, but they’re often empty.”
Success with growing walnuts depends on several factors – climate, drainage and irrigation among them. Walnuts are susceptible to fungal and bacterial diseases in damp climates, and root diseases including phytophthora in damp soils, so trees are best suited to drier areas with an annual rainfall of under 600mm.
They need fertile, free-draining soil with good irrigation, and must be protected from wind, or their branches will break. Late spring frosts can be a problem for some cultivars too. “‘Franquette’ is a late-producing variety and is the best walnut for frosty areas that I know of,” says Nelson.
Walnut blight is exacerbated by wet and humid spring conditions; Auckland and Northland’s climates are too humid for growing these nuts. But regular sprays with copper are effective in managing the disease elsewhere. Spraying at bud burst is best, though exact timing is different for different cultivars.
“I spray about eight times a year, between the 1st of October and the 14th of December,” says Tony Sigmund, who with his wife Ngaire has planted more than 400 walnut trees on their property in West Melton, near Christchurch. “I use ManKocide, a mixture of copper hydroxide and Mancozeb.”
The use of ManKocide is common practice in commercial orchards. In local trials, sprays without copper proved to be completely ineffective, and spray programmes that relied on copper alone were somewhat effective, but inferior to those using ManKocide.
The majority of the Sigmunds’ trees are grafted ‘Rex’ and ‘Meyric’ types, but they have other varieties as well. “They’ve all had good and bad attributes over the past 15 years,” says Tony. “Some are hard to train, some are very susceptible to blight. At the moment, I like ‘157’ and ‘G120’, because they’re a big nut and fall out of the shell cleanly. The only problem is blight, so we have to spray with copper regularly.
“‘NZ Purple’ is hard to get going, but everyone loves the nuts. ‘Stan’ and ‘Tehama’ are also a big nut and fall out of the shell easily, which makes harvesting easier.”
For home gardeners, though, Tony also recommends ‘Rex’. “It’s small and compact and easy to prune. It’s also less affected by blight. The only drawback is that the nuts are a smaller size, though they’re still nice to eat.”
The Sigmunds’ trees are pruned to a single leader with branches every 300-600mm. “This has been the standard practice, but as with all farming practices, some like to
Success with growing walnuts depends on several factors – climate, drainage and irrigation among them
If you have too many to handle, keep your walnuts in the freezer to protect the good fats they contain
prune lightly, and some like to prune heavily.”
Walnuts are harvested in autumn from the end of March to early May, the timing depending on the cultivar and the weather.
“It's best to get the nuts off the ground as fast as possible,” says Jenny. This prevents moisture spoiling the nuts and deters rats.
“Wash the shell if it's dirty, then get it dry as quickly as possible. This will take an afternoon if they're left in the sun and rotated. The kernel will be softer and pliable at this stage, and as a rough guide needs to dry in an airy place till it snaps. The length of the drying time will depend on weather conditions and temperature, but six weeks is again a rough guide.”
Larger orchards use mechanical harvesting equipment complete with sweepers and vacuums, and home gardeners have options too. The Horwells use the Lourdan Grove NutHarvester. “It's held like a broom and rolls along the ground collecting the walnuts in a wire frame,” says Jenny. “It saves a lot of backache.”
And what can you do if you find yourself with an abundance of nuts? Eat them raw, cook or bake with them, or pickle them. Or if you have too many to handle, keep them in the freezer to protect the good fats they contain, says Jenny.
“You can use them straight from the freezer and enjoy them as fresh as the day you put them in there.”