Growing down under

Article originally published by: Kiwi Gardener

Ensure you have the right magic happening in your soil to encourage bumper crops of your favourite root vegetables.

Life in the garden starts and finishes in the root department. Poor soil equals poor results, so it’s really a no-brainer to invest a little time and effort into soil preparation before you start sowing and planting any root crop.

Last month we went over some root vegetables, such as potatoes, parsnips and garlic, all of which needed to be in the ground well before Christmas, so this month is all about what you can plant now.

Carrots, beetroot, salsify (oyster plant) and radishes all have delicate roots that need to be able to anchor themselves deeply into the soil, therefore it is important they don’t tangle, twist or distort if you want a straight, evenly-round, healthy crop.

The aim is to get the soil well dug over and free of any lumps, stones, sticks and clods. Working compost into heavy soils helps, as does sifting the soil if your area is particularly stony or lumpy.

Many root crops are happy in containers. Specially blended potting mixes are loose and light, which is ideal for the young roots to wriggle down into. Ones to try are beetroot, carrots, radishes and spring onions.

Numerous root crops can be sown in the same row, at the same time – for example, radishes and carrots work well together, as do beetroot and carrots. Swedes and turnips are also easy companions and have similar growing periods.

L-R: Celeriac, Carrots, Beetroot, Spring Onion, Swedes & Turnips


Now, this is a crop for people who have a little patience – like about six months of it! Celeriac looks like celery above the ground, with its lush-looking leaves, but it forms a large, knobblylooking, round head below the soil. Celeriac not only needs time, but a little space. Allow about 20cm between each plant. Fortunately, a period of cold weather, frosts and the like actually enhances its flavour. You can sow seed now or get your hands on some seedlings. Celeriac prefers a moist soil over summer to help it develop its large bulbous head. Two main varieties are available as seed: ‘Giant Prague’ and ‘Mars’. It is an easy crop to grow in larger tubs and containers, and as it’s so attractive, you can happily position it in an area you will see often. The leaves can be used, too, although don’t take too many off at once as it will limit the plant’s ability to grow.


The essential thing with carrots, as with most other root crops, is to prepare the ground well in advance. The soil needs to be loose and friable, so the young roots can easily bury themselves into the ground. Lumpy or stony soil will result in misshapen carrots. Some carrots appear as seedlings in the shops, and while these are fine to plant, they will never produce the same quality of carrots as those sown direct from seed. Sow in rows about 30cm apart, and mark the front and ends of the rows, so you know where they are. Little wispy seedlings will appear in a couple of weeks. Aim to keep the soil slightly moist – not wet, but not dry. A great trick is to blend two different varieties of seed together, for example purple carrots with orange ones. This makes harvesting fun, and it looks fabulous too. Thin the plants out so you can fit at least two fingers between each plant; good spacing allows plenty of air movement between the plants, helping prevent aphids and greenfly from appearing.


How good is this vegetable? It has to be near the top of the table for versatility, with both the roots and the leaves being edible. In an ideal world, beetroot seed should be sown directly into the ground. Being a root crop, any time the roots are handled risks damage to the root; seedlings do grow well, but handle with care. A top tip is to look for the smaller seedlings, as the larger ones are easier to damage when transplanting because the roots will be more intertwined. The long tapered varieties are best grown out in the garden whereas the round globe ones are perfect for pots and tubs. Try planting some of the rainbow-coloured ones; the yellow and white ones look neat and still have that great beetroot taste.

Spring onions

You really have no excuse not to have spring onions in the garden, especially if they are a staple on your menu most weeks. They take up such a small amount of room and are very low maintenance to grow – no tying or staking with these steady salad greens! Buying seedlings speeds up the growing process by at least six to eight weeks. Growing them from seed is easy, however, the seedlings are so fine and delicate – and worse still, fiddly to prick out – that it is just easier to buy some that are ready to plant out. Ideal in tubs and containers, too, a 10-litre kitchen bucket is big enough for a couple of punnets. You can plant the whole plug at the same time if you like; this makes harvesting easy since they can all be picked at once. Look for the new red-stemmed varieties, these are slightly sweeter in taste and look fabulous in salads and stir-fries.

Swedes & turnips

Here are another couple of crops that do their business below the ground, ready for harvesting in the winter months. To get the best results with swedes, the seeds need to be sown this month. Sow turnips and swedes in rows, then, once they are up, thin out the seedlings to allow at least 15cm between each plant, especially swedes. They will cope with longer dry periods if they have to, but the risk with not watering often enough is that they can bolt and run to seed. Swedes are another long-term crop, so allow six months for them to mature, whereas turnips only take three to four months to develop. Sow turnips in February or March.

L-R: Radish, Jerusalem Artichoke, Yams, Kumara, Salsify


This is the speediest root crop around. These peppery nuggets of crunch and texture are ready to eat within six weeks of sowing the seed. You won’t find seedlings around at all, due to the seed being so quick to germinate. The first leaves will be poking above the soil within a week, and then they quickly get the job done. The leaves can be eaten as well, however, once they get longer than finger length they start to get too hairy and feel terrible on the tongue – think peach skin, but 50 times worse. Radishes are ideal in patio planters, troughs and window boxes. The round ones only need 15cm of soil depth, and the cylindershaped ones need about 25cm of soil depth. These are an ideal crop for kids because they grow so quickly. A fun idea is to get the kids to sketch out their names in the soil and sow the seeds in the furrows, so, when the seeds germinate, they grow in the shape of the letters. If you’re looking for something different, Egmont Seeds has listed a new black radish for this season – it could well be worth a try!

Jerusalem artichoke

These knobbly, rather unattractive-looking root vegetables may look like they would be hard work to grow, but they are super easy. You main consideration needs to be planting them near the back of the garden or somewhere where they can grow up to their eventual height of over 2m. Plants will appear briefly in the garden centres, however, they are usually sold at farmers’ markets and through online heirloom seed catalogues. Simply nestle the bulbs under the ground, and within a month you will have new shoots and they will romp away. Lovely, small, sunflower-like flowers appear later in summer adding to their appeal. One caveat though – their nickname is ‘fartichokes’, so if you have a sensitive tummy, be aware that wind might be on its way.


It is getting fairly late for yams now, however, if you can find some seed or get some from the supermarket you will be in business. Don’t worry about sprouting them now; put them straight into the garden. Yams are part of the Oxalis family, so what that means is that yes, they are very easy to grow, but if you leave a yam or two in the garden they can easily become a little invasive – however, if you love yams that usually won’t be a problem. Plant them in shallow rows, and as the foliage appears above the ground mound the soil up around the leaves as you would for potatoes. This forces them to produce more tubers, thus increasing your harvest. A side-dressing of potato fertiliser works wonders, and a deep watering once a week is enough in summer. Harvest after the first frosts in May or June.


Our wonderful sweet potato is a crop for the warmer regions only, and the runners need to be planted out before Christmas into a well-worked rich soil. Once the foliage starts running, it grows rapidly, covering large areas in a matter of months. Trim back any runners that may scramble over lawns and paths; this does the plant no harm. As the runners are developing in February and March, aim to water the plants deeply as least once a week. Kumara are ready when the foliage starts to wilt and shrink. Allow six months from planting to harvest for these too, and give them a bit of room – at least 1m per plant.


Are oysters your thing? If they are, then you will probably want to grow some salisfy in your garden. It grows in a similar way to carrots, with a long taproot under the ground, and needs a warm spot to thrive. Cultivate and prepare the soil as you would for carrots, then sow the seeds in rows, thinning to a double-finger spacing apart once the plants are around finger-height. After a few months, tall stalks of lovely soft-purple/ pink flowers appear, adding to the charm of the plant. Salisfy is easy to cook; prepare as you would a carrot, sauté in butter, or add to soups. Seeds are widely available online through Kings and Egmont seed companies.