Gardening: Hard nut to crack

Just when I thought I was getting on top of the idea, if not the reality, of a sustainable food garden, I realised something was missing.

A friend just happened to mention the walnut tree they had in their garden when he was a kid, and whammo, I was on a nut bent. It was exacerbated by my recent visit to the South Island, where quite a few people are growing nuts, having outgrown (oops) the trendiness of such newbies as celeriac and kale.

This is not the time for planting nuts, of course, but it's certainly the time for thinking about them, especially if friends are likely to give you home-grown nuts as Christmas gifts and feed your sense of inadequacy.

A surprising number of different nut trees grow in New Zealand. My thoughts turned immediately to pinenuts, driven by the heart-stopping price tag they carry in the supermarket. I'm certain they price them per 100g and not by the kilo to lessen the chances of cardiac arrest among their nuttier customers.

Heaps of the Pinaceae family have edible nuts but only a few are commercially cultivated. Pinus pinea is the most commonly grown here, far from its origins on the Mediterranean coastline.

Those origins make it an ideal tree for exposed coastal areas - it has a strong taproot, which can penetrate hard soils when looking for water during hot, dry summers. It'll also tolerate salty air, high winds and temperatures in the negative.

Wet soil is the pinenut's nemesis, because the taproot struggles to develop and the tree is inclined to blow over. Assuming it doesn't, you'll eventually have a 15m- to 20m-high tree which, despite its bounty, may not endear you to your neighbours.

It takes about six or seven years for the tree to begin producing cones and it won't reach full production until it's about 40 years old, so, if you're already retirement age, perhaps choose something faster. Furthermore, by the time it's delivering the goods, you'll be too old and grumpy to be bothered trying to get the nuts out.

The mature cones need to be hooked with long poles from the branches or harvested mechanically with tree shakers, then laid on tarpaulins to dry in the sun and release the nuts. The theory is the nuts will fall out of the cone but many are reluctant and have to be put through rollers to crack off the shells.

So, walnuts, then. Much simpler.

First, you need at least a space that's a minimum of 5m in diameter .

Plant during winter in fertile, well-drained soil, in a sunny, sheltered spot. Walnuts don't love frosts, especially in spring when the flowers can be damaged. They need plenty of water when the fruit is developing to produce good-size nuts.

Prune annually to shape the tree, but once it's looking as you want, just remove excess twiggy growth.

Pick up the walnuts as they fall to the ground, and either dry them for storage, or eat them.

There's certainly space for a walnut tree at our place so that's on the wish list but, to be on the safe side, I'll probably have to grow a macadamia as well. It's a shame because, despite the fact that the nuts are gorgeous and the macadamia flower is very beautiful, the trees, I reckon, are pig ugly.

I can never figure out why a tree that likes a tropical climate should look prickly, dried up and half dead.

Macadamias like soil rich in organic matter with good drainage, a pH balance of 5-6, plenty of light, protection from wind when young and average rainfall. Frosts and wet feet are no-nos.

You can prune after planting to reduce the tree to two leaders at each branching, and trim the tree to allow for light, ease of picking and good air circulation in the centre.

The pecan is a member of the Hickory family. It originated in North America but pecan trees have been growing in New Zealand for more than 100 years. They seem to do quite well from the top of the South Island and throughout the North Island, and there are cultivars available that suit other climates.

Close to 200 frost-free days are needed through the growing season for nut production and temperatures need to be warm enough to sustain an adequate growing season, with a chill spell during the winter dormancy. The pecan can stand heavy frosts when dormant, but late frosts prevent fruit setting.

Pecans are native to river and creek bottoms, the soils of which are deep, fertile, well-drained and have substantial water-holding capacity, so any planted in shallow soils will have trouble developing to their full potential.

If you want to sound incredibly knowledgeable if the subject of pecans ever comes up (don't hold your breath), you can trot out the fact that it is not in fact a true nut, but a drupe - a fruit with a single stone or pit surrounded by a husk.

It's also where we get the expression "a hard nut to crack", since the name means a nut that has to be cracked with a stone.