There’s hardly a crop more ubiquitous in our diets, and in our cooking, than the potato
The part of the potato plant we eat is familiar — an oval-shaped, thin-skinned, pitted tuber — but the top growth of the plant may not be so recognisable. It grows to around 75cm high and 45cm wide with rigid, slightly hairy stems and green leaves. The clusters of white to mauve nightshade flowers hint that potatoes are part of the large Solanaceae family. After flowering, round green berries form, but the plants are grown from tubers, not these seeds.
In their native South America, potatoes come in a staggering array of shapes, sizes and colours. In just four centuries, they’ve conquered the world to become one of our most important food crops.
Site and soil
Potatoes flourish in a rich, friable soil tilled with well-composted animal manure or added organic fertiliser. Don’t grow them in recently limed soils and don’t put tubers in direct contact with manure or fertiliser. They don’t tolerate frost, either, which kills the top growth. Select a sunny, well-drained position. Alternatively, plant potatoes in mounds of organic straw or sugarcane mulch.
Planting
Although potatoes grow from sprouted spuds (just cut potato into 50g segments, each with an “eye”), these may introduce virus diseases. It is recommended that gardeners buy certified seed potatoes (small, virus-free tubers) from garden centres or online. Look for organically grown.
Allow seed potatoes to sprout with small stubby shoots before planting. They are best grown between February and August in the tropics and subtropics (to avoid the wet season); July to October and January to February in temperate zones; and August to December in cool or frosty zones.
Growing
In a garden bed, plant seed potatoes in rows 15cm deep and 25–30cm apart. Set rows 60–80cm apart. In a mound system, lay straw one biscuit thick, add seed potatoes, organic soil and compost, then cover with another straw layer. Keep layering as the stem grows. Keep plants mulched and tubers well covered with soil. Potato plants need to be watered regularly, especially as they begin to flower. Provide an occasional feed with an organic liquid fertiliser.
Harvest and eat
Tubers mature after flowering and are ready to harvest at around 12 weeks, when the leaves yellow or the tops die down. Small “new” potatoes may be ready four weeks from flowering but are not suitable for storing because of their very thin skins.
Problems
Caterpillars and 28-spotted ladybirds may attack leaves. Control aphids as they spread virus disease. Potato moth attacks tubers. Excessive wet weather or poorly drained soil can lead to fungal diseases such as blight; affected tubers are unsuitable for storage and may be inedible.
Companion plants
Beans, cabbage, tansy and coriander.
Written by Diane Crawford
Originally in Good Organic Gardening Volume 4 Issue 2
