The Miracle of  Growing Food Regeneratively

Creating Local Food Security & Healthy, Vibrant, Regenerated Living Soil, & Nutrient Dense Food

GROWING TUBERS

CONTENTS

1. OCA

2. POTATOES

3. SWEET POTATO (KUMARA)

4. ULLUCO

KUMARA - see SWEET POTATO

Soil & Feeding:

Like potatoes, they love rich ground, so mix in two buckets of well rotted garden compost per square metre + two handfuls of Eco or Organic Fertiliser, per square metre (yard).

Varieties:

Ocas come in a whole range of colours and you can get a ‘rainbow’ mix from some sources, but I bought some pink ones from the supermarket and planted them.

Planting:

Oca is frost tender and prefers light soils, but any well-drained soil will do. Plant the tubers after the last frosts 75mm (3in) deep, 45cm (17½in) apart in rows 60cm (2ft) apart.

Growing:

Earth up the plants as they grow, as you would potatoes, leaving 20cm of the tops showing.

Harvesting:

Lift the crop as late as possible, when the tops are quite dead. The tubers need as long a growing season as possible and only really put on weight towards the end of the growing season. If you harvest too early you will not have much of a crop.

Possible Pests and Diseases:

Ocas are largely pest and disease free, but some have found in wetter areas and in wet seasons, slugs can attack the plants and they can also get a rust fungus on the leaves. Here in Nelson though, I have not had any problems - (see: section ‘Pests & Diseases’ – Beer Traps for slugs and Trichoderma virid spray for fungus).

Soil, Feeding & Planting:

Here’s your chance to really make great strides in creating a healthy, vibrant, living soil full of organic matter. This was how we transformed our first garden at our farm:

1. Clear the plot of weeds or previous crop, especially perennial weed roots, like couch and bindweed.

2. If you have enough well rotted manure or compost spread one bucket every square meter + seaweed meal at the recommended rate (optional) 3. When the last frosts have come and gone, mark out the rows with sticks at each end – earlies need 45cm (1½ft) between the rows – Main crops need 67cm (2ft) between the rows.

4. Dig out a trench, one fork depth, placing the evacuated soil into a wheelbarrow.

5. Line the bottom of the trench with 7cm (2¾in) of well-rotted manure or compost.

6. Spread about 3cm (1in) soil on top of the compost and place out your sprouted potatoes “rose” end upwards on the soil – 30cm (1ft) apart for earlies – 37cm (15in) apart for main crop.

7. If you want some of your main crop potatoes for baking, then break off all the buds except two, this will result in bigger potatoes. If some of your seed potatoes are very big you can slice them in half down from the ‘rose’ end, or 3 pieces, as long as there are at least two buds on each bit.

8. Fill in from the next trench and repeat the process all down the bed, filling the last trench in with the soil in the wheelbarrow from the first trench.

9. The rows will be marked by the raised rows.

Alternatively grow them the No-Dig way:

1. Spread two buckets of compost or well-rotted manure per square metre (yard). Then use a garden trowel to make 15cm (6in) deep holes and drop the potato, ‘rose end’ upwards, down the hole and fill in with soil from the next hole – at the same spacing as above.

2. Water the whole bed.

3. Then spread 15cm (6in) of spray free straw over the whole bed.

4. As the new growth starts to show through the straw mulch, add more straw – up to 30cm, topped with grass clippings to stop light effecting the new potatoes and turning them green.

Varieties:

You may have one type of early potato you like and one type of main crop. For the main crop there are basically two main types – Waxy and Floury. We like both for different jobs in the kitchen. There are so many heritage and more modern varieties, that it would be impossible to list the hundreds that exist. So, here are the ones we love and recommend, along with their qualities and uses:

Earlies

Jersey Bennes – Matures in approximately 80-90 days. They are oval shaped, with white skin and white flesh. A waxy potato, good for boiling, salads, casseroles, and soups.

Rocket – Matures in approximately 60-70 days. They are oval with white skin and flesh. Great boiling and roasting potato.

Maincrop

Desiree (Waxy) – Matures in approximately 90-100 days. They are round with pink skin and cream flesh. Good for all general cooking – a good all rounder.

Agria (Floury) – Matures in Approximately 90-100 days. They are long fat ovals, with a cream skin and yellow flesh. Floury potato, suitable for boiling, mashing, baking, wedges, and great for chips. High yielder.

Pink Fir Apple – (Heritage). This late main-crop variety produces long, knobbly, pink skinned tubers with butter yellow, waxy flesh, and a distinctive nutty flavour.

Urenika – (NZ Heritage). A long potato with dark purple skin that retains its colour when cooked. Waxy when small, floury when large. Great boiled or steamed. Produces big crops but needs a long growing season.

Kowiniwini – (NZ Heritage). A round, light purple potato with indented white eyes and a waxy firm flesh. Great keeper.

Growing:

As the plants grow draw the soil up from between the rows around the plants, this is known as ‘earthing up’. If a lot of weeds sprout, another earthing up on a dry or sunny day should kill them.

Frost Warning: If there is a warning of frost when the shoots are still short, especially with early potatoes, they can be covered with soil to protect them. They will then grow through. If they are too big to cover with soil, then spreading loose straw over them, several layers of newspapers held down with canes, or cover with frost fleece. This will protect them temporarily against late frosts, taking the protection off in the daytime, but remembering to put it back in the evening.

When the plants start to get higher than 30cm it is time to place canes or stakes at the corners and tying 3 or 4 rows of strong garden string round, so as to stop the plants falling over in the wind.

Spraying every two weeks with liquid seaweed, and/or compost tea will help to keep the plants healthy – (see How to Make Liquid Manures in section ‘How to Build Fertility’. 

Harvesting:

For early potatoes, just fossick around under the plant and harvest the ones that are ready to enjoy fresh. Later you can dig up the tubers as described below. They won’t keep as long as the main crop, so enjoy them before the main crop harvest.

For the main crop you can wait until the haulms have died down, unless you have a late attack of potato blight, in which case cut the haulms off and put them out with the rubbish, not in the compost, to make sure they will not infect next years crop. If the haulms have been infected, leave the tubers in for 2-3 weeks before harvesting to kill the spores and harden the skins so they store better. Always leave for 2 weeks to harden the skins.

When harvesting thrust the fork in from the side of the ridges and lever the tubers out. Don’t dig along the ridges, because you will more likely spear the potatoes and they won’t keep!

If you grown them the No-Dig way - just remove the mulch (for the compost heap) and pick up the potatoes. You may have to rummage around for some that are just under the soil. This is one of the great advantages of this way of growing them – less work!

Storing:

Spread the tubers out on sacks to dry in the sun, then sort through them and put any damaged, or any with a sign of rot to one side, to either eat within a few days, or throw away. Then store in hessian bags, or other woven bags in a cool frost free shed or store. Paper or polythene bags will cause condensation and rotting. About a month after storing away, sort them over to remove any that are rotting, as this will spread to others. Remember, potatoes are the most important bulk crop you will grow.

Possible Pests and Diseases:

Tomato/Potato Psyllid

As potatoes are members of the Solanaceae family (tomatoes, egg plants, peppers, etc.) they are subject to the same diseases, the most important at the moment here in New Zealand is the tomato/potato psyllid native to North America which was first found in New Zealand in 2006, and is still spreading throughout the country. In Australia it is present in Western Australia the tomato potato psyllid apart from the Perth quarantine zone. However, many other countries (like the UK) do not have this pest.

Psyllid Nymphs and possibly adults inject bacteria into the plants when they feed. This bacteria causes discolouration of leaves and the plant becomes stunted and the leaf edges turn up and become yellow or purple. The plants internodes shorten, new growth is retarded and crops are severely reduced and the resultant potatoes end up small and watery with ‘zebra’ stripes, becoming inedible.

In potatoes, however not all host plants show ‘toxic’ plant reaction symptoms and interestingly if the psyllids are removed early, the plant may start to grow normally again as soon as the bacteria ceases to be injected by the psyllid mites.

Control

Interestingly the psyllid seems to favour the tomatoes, leaving the potatoes, peppers and egg plants less likely to be affected, this said, I seriously suggest using several effective ways to help control psyllid. I currently am using three methods, plus Neem oil spray when necessary.

1. Neem Granules: Neem granules are usually used to control soil and root pests, but have also been used by sprinkling a small handful in each planting hole when planting the potatoes, or sprinkling the granules along the row when using the trench method of planting. For more details, see: www.gardenews.co.nz and click on The Potato and Tomato Psyllid section.

In the soil the Microbes break down the granules releasing the Neem properties that are still in the granules over time. These properties are taken up by the roots and translocate through the plant. Thus if a chewing or sucking insect feeds on the plant they receive a small dose of the Neem affecting their ability to eat again. Thus they die of starvation.

I was worried at first that the Neem might interfere with the beneficial soil microorganisms, but it seems they actually increase, and conversely, the beneficial effects of the Neem are increased where there are strong soil microorganism populations.

Neem oil comes from the Neem tree fruits and kernels. These are crushed for the oil, and the resultant cake is broken down into granules. The granules contain the active ingredient Azadirachtin. Azadirachtin is known to affect over 200 species of insect when they eat it, and by acting mainly as growth disruptor, whilst showing very low toxicity to mammals. According to my research, it seems that Azadirachtin has no effect on earthworms and a limited effect on mycorrhizae fungi.

Azadirachtin also has a high nutrient value, as well as increasing the availability of the soil’s natural nutrients by stimulating soil micro-organisms, providing more nitrates for the plants and helping to break down organic matter into valuable humus.

2. Diatomaceous Earth: This is a powder made from diatomaceous limestone, made when millions of years ago, small diatoms fell to the sea floor and built up into a unique form of limestone. The tiny bits of powder are sharp and punture the insects sucking them dry and killing them.

Place the powder in a plastic drinking bottle

Potato Blight

This is caused by the fungus Phytophthora infestans, which killed a million people from starvation in Ireland and many more in Scotland and Northern Europe in the 1840’s. Many of the more modern varieties are more resistant. My grandfather worked in conjunction with the UK’s Rothamsted Experimental Station in the First World War period on developing resistant strains.

As there is no cure, the traditional organic preventative spray is Bordeaux Mixture, made from copper sulphate and lime, sprayed on every fortnight in dull warm wet weather that favours the spread of the fungus. Personally I stay away from copper sprays, as they interfere and can even kill soil life, especially mycorrhizae fungi, if used regularly. A safe alternative that is worth trying is Trichoderma viride powder made into a spray. Trichoderma is a fungus that eats other funguses. It might be worth spraying with Trichoderma every two weeks as a preventative measure if you have problems with potato blight.

Fortunately I have found over 40 years of growing potatoes organically, even when we grew 6 tonnes a year on our farm in the UK; most years in the English climate we got away with it until late in the growing season. As soon as the leaves were starting to blacken, we chopped the tops off and waited at least 2 and preferably 3 weeks before harvesting in order to allow the spoors to die off, so they would not infect the tubers.

If you leave the tops on too long the blight will grow down the stems and rot the tubers, so catch it early. Cut the affected tops off and dispose of them in your waste bin. Don’t try to compost them in case the blight is carried over to next years crop.

Creating a healthy vibrant soil (see the section – 'How to Build Soil Fertility') and spraying regularly with seaweed and compost tea will help to control the disease, at least until the last minute.

Soil & Feeding:

Kumara is best grown in a warm climate that has a long hot summer. In cool areas you will need to protect young plants from frost in the spring, or try growing in a glasshouse or Polytunnel. Do not add manure or rich compost, as this will encourage top growth at the expense of roots. However, wood ash and seaweed can be added for extra potassium and trace elements. Ground charcoal can also be added to darken and warm the soil, and will also encourage a good growth of beneficial soil microorganisms (see: TERRA PRETA in the section ‘How to Build Soil Fertility’). Don’t be tempted to fertilise while plants are growing, because this will encourage leaf growth as opposed to tuber growth. However, regular sprays of liquid seaweed will help to keep the plants healthy.

Varieties:

If you can’t obtain the varieties below, you can buy some sweet potatoes from the vegetable section of your supermarket and sprout them as described. In many countries you can buy the sprouted shoots in the spring to plant out. There are a huge number of varieties, so I have listed only a few of the best heritage varieties from New Zealand and a selection from the United States.

New Zealand Varieties:

Candy – A stunning kumara with candy pink skin and pink and yellow flesh. Sweet, good flavoured flesh, which retains its pinky colour when cooked. Very nice roasted or boiled and looks amazing mashed with onion, garlic and cheese as a pink stuffing for baked squash.

Honey Red – Beige coloured skin with a faint orangey-red blush in places. Flesh is pale with light orangey-red colouring throughout. When cooked the flesh is firm and orange, with good flavour.

Hutihuti – An ancient kumara that is a super long white skinned and fleshed variety, prolific cropper with a good flavour. This has been a widely grown and loved kumara all over Maoridom.

Maikio Red – This was originally from commercial stock and especially selected for keeping and disease resistant qualities. It is a good productive main crop kumara.

Reka Rawa – A reliably large, old, cream skinned and cream fleshed variety. Also the best cropper! This is the ultimate kumara, it tastes very much like roast chestnuts. From an ancient Far-North collection.

Romanawa – Another very old kumara remembered perhaps better than all other old cultivars by elders all around this land. It has gold skin and yellow flesh but with orange rings within the flesh when cut in half. It is very sweet and of a medium texture, not too dry or soft.

USA Varieties:

Sweet Potato Name & Origin / Skin Colour / Flesh Colour

Allgold (Oklahoma) / Tan / Orange

Brinkley White / Creamy White / Creamy

Bunch Porto Rico / Yellow-Orange / Yellow-Orange

Continental Red / Pink-Red / Light Orange

Cordner (Texas) / Copper / Medium Orange

Dianne / Reddish / Dark Orange

Garnet / Red / Orange

Hannah (Yellow Hannah, Sweet Hannah) / Light Tan / Light Yellow

Hawaiian Blue – Pale coloured skin /Bluey-purple flesh / good flavour

Hernandez (Louisiana) / Burnt Orange / Deep Orange

Jewell (Carolina) / Copper / Deep Orange

Porto Rico (Carolina) / Rose-pink / Orange Mottled

White Delight (Georgia) / Purplish-pink / White

Sprouting the Shoots:

You can buy young plants, but if you want to try growing your own, then here’s the way.

In late winter, early spring start by sprouting Kumara shoots. Use a deep polystyrene or plastic box with drainage holes and a clear plastic or glass lid. Line the bottom with 10cm of grass clippings, or horse manure that is just starting to rot to provide some heat. Cover that with a layer of straw and top it off with a few centimetres of sand. Push a couple of kumara tubers into the sand layer, then water and cover. Keep the seedbed well watered.

As the grass clippings or manure heats up, the kumara will sprout vigorously. Lift the lid to allow for air circulation to prevent mildew and fungal problems. The sprouts can be cut off the tuber when they’re about 5cm (2in) high and the roots are showing, these can be easily separated from the loose sand. From a single tuber, it’s possible to get a dozen new plants. This will take approximately 4-8 weeks. If they are ready too early, you can pot the rooted shoots in a deep box containing potting compost. Keep in a glasshouse, cold frame or conservatory, until it is time to plant out. In warmer areas kumara can be planted out from early to late spring. In cooler areas you should wait until general risk of frosts has passed before planting – usually sometime around late October in the southern hemisphere and late April in the northern hemisphere.

Growing:

The kumara bed should be made with free draining, coarse river sand which prevents the sweet potatoes from rotting in the spring rain, and only has a small amount of nutrients, so it doesn’t support lots of weed growth. Kumara are grown in a free draining loose soil, with a hard pan about a foot under the surface. If you don’t have a clay pan under the soil bury something like corrugated iron a foot under the soil to act as a hard pan. This is one vegetable where deep and thorough digging is therefore to be discouraged. If your soil is too heavy, the skins will be covered in a patchy brown virus, so adding sharp sand to the top layer of soil will help.

Plant 10cm deep; bend the roots of the cuttings under, into a J shape when planting so the roots face up to the top again under the ridge of soil – this will prevent the vines from spreading too far. As the vines grow, the stems will try to put down new roots where they touch the soil, you want to avoid this, so lift the foliage regularly to stop secondary rooting, some people curl them around in a circle. This is to encourage tuber growth and not leaf growth. If space is limited you can take out the tips later on to prevent the vines smothering other crops. The tips are good steamed or in (like spinach).

Usually there is enough rain to provide the moisture required, but if there is a dry spell water regularly to keep the sand moist, otherwise the kumara won’t grow properly.

Kumara can be grown in containers. Pots need to be at least 30cm (1ft) deep and will require plenty of water through the summer to ensure good-sized tubers. Sweet potato is usually trouble-free in the home garden but don't plant it in the same spot for at least four years.

Harvesting & Curing:

Wait until the weather is cooling, early autumn at the earliest – sweet potatoes don’t start swelling up until then.

Harvest from the end of March (Southern hemisphere) or September (Northern hemisphere)once leaves start to die down or turn yellow in the autumn. After that the drop in daylight hours and temperature means that tubers don’t really increase in size, and there is a risk of the weather becoming too wet and cold, which makes them harder to dry and can reduce their storage capacity and they could even rot.

Use a sickle, or shears, to cut the tops off the plants following the shape of the ridges and make sure that the main stalks remain visible so you know where to dig. You can add the tops to the compost heap, or on a large area you can trample the tops down into the furrows, where they are left to break down into the soil.

Dig them up carefully without breaking them, as they will rot in store if broken. Cure them thoroughly. They can be laid out in the sun if it’s hot enough; otherwise put them in the hottest place you can organise. You can make an insulated ‘micro-house’ inside your glasshouse, keeping them at 30-350C (86-950F) for about a week. This heals any cuts and breaks in the skins, so they don’t get infected.

Storing:

The best ones should be selected for growing next years shoots – not the biggest, but ones with good colour and form for that variety, and with no skin blemishes. These are best stored in wooden boxes with dry hay around them to protect them from rubbing against each other and being bruised.

The rest for eating are then graded within each variety into large, small and damaged. The damaged ones should be eaten as soon as possible. The eating kumara are put into hessian sacks and stored stacked up. Store them in a warm, dry place where the temperature doesn’t drop – commercially they are stored in heated ‘warm stores’ for the winter. Ideas at home include using a cardboard box in a warm room or glasshouse, with newspaper separating the layers of kumara.

Possible Pests and Diseases:

Rotate your kumara, by moving to a new site each year and not growing kumara on the same area for three or four years, is the best way to stop the build up of pests and diseases. Black beetle, crickets, nematode and white fly caterpillars are the usual kumara pests, which can be dealt with using organic and biological sprays (see: section ‘Pests & Diseases’).

There are some fungus diseases of kumara, but again judicious crop rotation and the suggested growing conditions already described should keep these in check.

Recipes:

Kumara Bravas

Feeds 7-8

Ingredients:

• 1 kg (2 pound) large kumara

• Oil for frying

• 2 tablespoons olive oil

• ¼ red onion, chopped

• 500g (1 pound) tomatoes

• 1 tablespoon smoked paprika

• Pinch of chilli flakes

• 1 bay leaf

• 1 teaspoon brown sugar

• 2 tablespoons parsley, chopped

• 1 tablespoon capers, drained

Preparation:

1. Peel the kumara and cube, rinse and pat dry. Cook in hot oil until golden, drain on paper towels. Keep the oil.

2. Chop tomatoes.

3. Heat olive oil in a large saucepan and cook onion for 5 minutes on a low heat. Add paprika and chilli and cook for another 1-2 minutes.

4. Add chopped tomatoes, bay leaf, sugar and ⅓ cup water. Cook until tomatoes are starting to soften but still whole – about 3 minutes, stirring occasionally. Cool slightly and remove the bay leaf.

5. Reheat the oil. Re-cook the kumara cubes ensuring they are extra crispy and drain on a kitchen towel – then place on a platter, and top with onion, tomato mix.

6. Garnish with parsley and scatter over the capers. Serve.

Kumara Glazed with Orange & Butter

Feeds 4

Ingredients:

• 500g (1 pound) kumara

• A little extra virgin olive oil

• 2 tablespoons Rapadura (or dark brown sugar)

• 2 tablespoons butter

• Juice of 2 oranges

• Juice of 1 lemon

• A pinch of nutmeg

Preparation:

1. Set oven at 180 C (356 F).

2. Place peeled & sliced kumara in a baking dish and brush with a little olive oil on both sides.

3. Cook in the oven for 20 minutes.

4. In a saucepan dissolve the rapadura with the butter. Cook until the mixture caramelises, then take off the heat and add orange and lemon juices and a pinch of nutmeg.

5. Pour over kumara and baste the kumara with the sauce every 10 minutes or so until they are cooked – approximately 30 minutes.

Soil & Feeding:

Ulluco thrives even in relatively poor soils. Light soils are better for harvesting. Moderately acidic soils are ideal, but Ulluco doesn’t seem to be too particular. It is better to add garden compost than anything stronger. Incorporate 2 buckets of compost per square metre (yard).

Varieties:

I have only seen them sold as Ulluco. There are a few named varieties, but I wouldn’t bother chasing them up.

Planting:

Plant Ulluco tubers in the spring after risk of frost has passed. It is not recommended to cut your larger seed tubers before planting, as they will rot. Plant the tubers 5cm deep at 45cm (18in) apart in rows 60cm (2ft) apart.

To give you a good start you can start the tubers in 10cm (4in) pots in a greenhouse, transplanting them outside after the last frosts when they are 5cm (2in) tall.

Growing:

It is important to keep the soil weed free, because the little plants are slow growing to start and can get easily swamped. Mound up the Ulluco a bit at a time as they grow, drawing the soil up from between the rows to form long mounds, being careful not to smother the young plants and to break the fragile stems. Ulluco remain smallish plants into midsummer before spreading to cover a much larger area. Ulluco tends to grow prostrate rather than erect and will eventually cover the area just like Oca.

Harvesting:

As with Oca, wait until the tops have died down, or killed by frosts before harvesting, because they put on weight at the end of the season. Tubers store very well in cool conditions as long as the air is not too dry, which may cause them to dehydrate. The tubers will become green when exposed to light, but this does not alter the flavour and they do not become toxic as potatoes do. Store them in boxes in damp peat in a frost-free shed or store.

Possible Pests and Diseases:

Slugs: love these plants in a wet season, especially when they are still small plants, however in a good summer there should be little problem – (see: Beer Traps (for slugs) in section ‘Pests & Diseases’.

Recipes:

In South America Ulluco with its high mucilage levels are often used to thicken stews. Ulluco tubers with high mucilage content are gummy when raw, but after cooking this characteristic is usually reduced or lost. The mucilage can easily be removed by soaking the tubers in water or parboiling before use. Ulluco tubers are usually cooked whole and take about the same time as potatoes to cook. The major appeal of the Ulluco is its crisp texture, which like the jicama remains, even when cooked. Because of its high water content, the Ulluco is not suitable for frying or baking but it can be cooked in many other ways like the potato.