Friday, 16 January 2009

Growing organic potatoes

by Rhonda Jean @ Down to Earth

Despite advice stating that potatoes should only be planted in the Spring, we grow potatoes all year long here. We are in a subtropical area with 1500mm of rainfall a year and no frost. Our temperatures range from around 2 or 3 degrees centigrade on a winter’s night to 40+ on a hot summer’s day. Generally though, our temperatures are fairly mild, and they tend towards warmth rather than cold. We are a two person family and if we are diligent in our planting, we don’t need to buy potatoes. Usually three crops per year is enough for us.

We plant potatoes from three sources – our own potatoes, store bought organic potatoes or seed potatoes, depending on what we have on hand and what time of the year it is. Our preference is a frugal choice – we plant our own potatoes from the last crop if we have enough of them. If we harvest small potatoes, or they send out a green shoot early – they are the potatoes we plant. When we harvest our potatoes, we keep the smaller ones outside ready for the next crop.

There are many different types of potatoes so choose the ones you like the taste of. For us, that is Dutch Creams, although sometimes we plant Kipflers, and we have tried other varieties. If you can buy local seed potatoes, buy them, if not, go to your organic green grocer and choose something from their range. If you’re not sure of the taste and qualities of the various types, buy some to test taste, then make your choice.

You need to think about your planting a long time before you plant – the soil needs to be prepared and your potatoes need to shoot. This is called chitting. To chit the potatoes, place them outside in the shade in old egg cartons, making sure rodents and dogs can't get at them The egg cartons will hold them nicely so they don’t roll around and break the shoot. Depending on the age of the potatoes, chitting will take between 2 – 6 weeks. Please note, you don’t have to chit the potatoes before you plant them. They will grow without chitting but if you can do it, you’ll have mature potatoes faster and you’ll be sure that every one of the potatoes you planted has sprouted. If you buy your potatoes just before you plant, just go ahead and get them in the ground, especially if you have the weather constraints of very cold or very hot weather. Potatoes take about 16 – 20 weeks to grow to maturity and it’s best to give potatoes their own bed as you’ll have to hill them.

Plant when all chance of frost is passed. Prepare the soil with old compost and cow manure but do not add lime, potatoes like a slightly acid soil of pH 5- 6. You must have good drainage or the potatoes will rot in the ground.

Never plant potatoes in old tyres – there is cadmium and heavy metals in tyres. While you can grow potatoes in potato cages and in no dig beds under straw, I believe the best potatoes are grown in soil. They mine the soil for minerals and it shows in the taste.

The potato bed pre-prepared here had been dug over, we always dig our vegetables, and although we know some gardeners prefer no dig we have found, that here, we only get high quality vegetables if we dig the soil, aerate it and add abundant organic matter between each and every planting. Adding lots of organic matter between plantings also helps reduce disease when you have continuous crops, as we do. So to this bed there has been added – homemade compost, old cow manure, blood and bone and the raked up floor of the chook coop – with decomposed lawn clippings, garden waste and old chook poo. None of these additives smell, they just have the scent of good garden soil because they have all had enough time to decompose. Adding fresh manure may burn your tubers.

Dig furrows in the garden bed about 75 cm (30 inches) apart. Plant the potatoes 15 cm (6 inches) deep, with the shoots pointing up, and with about 30 cm (12 inches) between each tuber. Rake the soil back over the potatoes carefully so you don’t break the shoots. Don’t press the soil down, but water well. Then mulch the rows. If you have any comfrey growing, chop some up and add it to the mulch, potatoes like comfrey. They like moist but not wet soil, so water according to your climate to achieve that.

Depending on your climate, shoots will appear on the surface of the soil in about two or three weeks time. As the potatoes grow, hill up the soil around the plant, just leaving the end tips of the plant exposed. You will need to hill the plants a few times. Always replace your mulch after hilling, especially if you’re in a hot or windy area.

Keep hilling your plants as they grow taller and try to build your soil up to about 30 – 40 cm (12 – 15 inches) by the time the potatoes flower. When you notice the potatoes flower, apply some diluted seaweed extract.

When the leaves at the bottom of the plants begin to go yellow, you will know you can bandicoot new potatoes from the side of the hills. To bandicoot potatoes, gently put your hand into the side of the hill at the base of a plant and feel for small potatoes. Remove any you find. This doesn’t disturb the main plant and will give you a real treat early in the potato season. A meal of new potatoes, fresh from your own backyard, is one of the many rewards of vegetable gardening that you never know about if you always buy your vegetables.

Spiced potatoes with sesame seeds.

Potatoes exposed to sunlight for a period of time will turn green. Never eat green potatoes, they’re toxic.

The potatoes in the photos above were planted here yesterday. Over the coming months, we will follow this bed of potatoes to harvest and then storage. Stay tuned.

POTATO FAQS from North Dakota University