The Back Yard

Justin Newcombe's tips for creating a gorgeous and productive garden

Gardening: The gardening revolution

By Justin Newcombe

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Crop rotation is a sure-fire way to get more out of your garden, as Justin Newcombe explains.

Crop rotation can lead to impressive growing results like this 925g tomato. Photo / Sarah Ivey
Crop rotation can lead to impressive growing results like this 925g tomato. Photo / Sarah Ivey

Crop rotation in gardening is like changing gears in driving. In hungry medieval Europe they had a two-crop gearbox, but things really moved along once they added a third. Then, in the spirit of sacrilegious experimentation, they added a fourth and before they knew it those wicked serfs were cropping like crazy. Their techniques have been handed down ever since as best-practice gardening.

Crop rotation is a way of stopping the soil from tiring, and also reduces pathogens, pests and disease.

Before a four-crop rotation the land was farmed or cropped every second year, then left fallow for a year. A 240ha estate was farmed 120ha at a time - not very efficient. Our basic rotation system is a four-step approach with some optional additions. Most crop rotation is focused on the production and depletion of nitrogen.

Here's a quick rundown of plants to use for each stage of the cycle.

1. Legumes
Most manure crops such as lupins are nitrogen fixers, that is, they convert nitrogen from the air into nitrogen in the soil. So do beans and peas. When planting, add pot ash from the fire. Once the nitrogen is fixed into the soil, the process of depletion starts (see my article on lupins here).

2. Leafy producers
Lettuce, spinach, cabbage and their like come next. Many people also grow broccoli and cauliflower here. I grow these as a separate "in between" crop as the flower head, which is the part you eat, performs a little better with a little less nitrogen in the soil.

3. Fruits
Tomatoes, eggplant, corn, pumpkin, watermelon and peppers all fruit well in a largely nitrogen-free soil, but I always plant them with compost because I want the plants to be nice and strong before they flower. If there is too much nitrogen in the soil you will have excellent leaf growth but poor flower set and small fruit.

4. Roots
Carrots, parsnip and beets all hate excess nitrogen but excel in the nitrogen-depleted soils at the bottom of the rotation cycle. I treat potatoes, kumara and alliums as a separate group which fit in between before roots and after fruits.

The medieval idea of leaving the ground fallow to refresh itself is not dead in the water either but rather enhanced by using a selection of herbs, grasses and flowers to revitalise tired ground. This is called a herbal ley, and is usually sown after fruits.

The idea is to give the ground a rev up before you plant alums and/or roots. One of the most popular plants in a herb ley is chicory, which is a deep rooting herb that mines trace elements and micro nutrients from deep in the soil structure. A herb ley is also a good idea if you aren't gardening in a space for a month or two.

If you haven't used crop rotation before I recommend you give it a go - it is one of the most fundamental gardening concepts. As my 925g tomato demonstrates, the results speak for themselves and no, I'm not showing off ...I'm just saying.

3 of the best: No-fail landscape plants

Canna lily
With an array of bright flowers and foliage that provides a sweet assortment of colour, cannas are plant candy, bringing plenty of lolly to any summer garden.

Nikau palm
With strong upright fronds, the nikau stands like a giant badminton shuttle, growing well in most situations.

Pseudopanx
The lancewood family do well in clay and wet soils, as well as standing up to a summer of beating sun.

- NZ Herald

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