There are many varieties of onions avaliable to grow in NZ. They vary in their pungency, size, colour and storage abilities. It pays to experiment with different varieties in your own garden to see what grows best. We stock a couple of onion varieties that have done well in Dunedin.
Spring onions are actually just young versions of regular globe onions, before the base of the stem has swollen. However some varieties have been selected that are more suited for harvest in this stage.
WHEN TO PLANT: Sow seeds Late summer to autumn, also early spring. Sow either direct in the ground, or start in trays for later transplanting. Onions grow slowly and are vunerable to competition from weeds, so planting out from trays is a good idea to give them a head start. Plant out seedlings in early to mid spring. In Dunedin, sowing onion seeds in trays in autumn yields more sure-fire results than sowing them in spring. They really benefit from the head start, to produce a good surface area of leaves which is then subsequently used as the powerhouse for bulb formation. The photo to the right is taken in September of onion seedlings sown in April and now ready to plant in the garden.
Plants planted in autumn require well drained soil to handle the boggy winter months. While they will have a decent head start come spring, they will still end up being in the ground for about 42 weeks until harvest, as opposed to around 24 weeks for spring sown onion sets or seedlings.
SOIL REQUIREMENTS: Onions benefit from the addition of plenty of well rotted compost or manure prior to planting, usually in the autumn. Some phosphate rich soil ammendments such as wood ash, bone meal or potash can be a good idea closer to planting time. Onions dislike acid soils so a light dressing of lime (or more if a soil pH test indicates strong acidity) can be a good idea as well.
Sandy but well watered soils are best for spring onions and quick maturing types, whereas heavier soils usually produce a slower maturing but longer keeping onion. Many people will lightly compress the soil around young plants by stepping on it around newly planted out seedlings.
Mulching with straw can be beneficial to hold moisture in the soil and prevent weeds.
SPACING: The size of the onions that you grow are somewhat dictated by their initial spacing. Seedlings planted out quite close together will result in smaller 'pickling' type onions, whereas those spaced further apart are able to grow to full size. As with many vegetables, and particularly root vegetables, just try to imagine the final size and shape of the root (and leaves) and plant accordingly. Try not to go too much beyond this spacing as it leaves the soil less shaded from the sun, and more open space for weeds to become established.
WATER AND FERTILISER: Provided that the soil is well drained enough, onions can handle relatively frequent watering. They can also handle long dry spells. Lack of water can result in an intensification of the flavour, but sometimes with the result of excessive bitterness or spicyness.
HARVEST AND STORAGE: In late summer the tops will wither and most will fall over. Bend any tops over by hand that do not fall themselves. Use the plants with the thickest / most brittle stems first as these are not as suitable for storage. About two weeks after tops bend, pull up the onions and cut off their roots. Lay them in the sun to dry, turning a few times so that they dry evenly over a few days. If the weather is wet, spread them on concrete or a wire net rack to avoid rotting, or spread them out under cover. Select clean, undamaged onions with a dry papery neck for long term storage.
WHEN TO PLANT: Garlic cloves are planted in the ground between June and August. You can buy 'seed garlic' cloves from a garden centre, save cloves from your previous years crop, or use garlic bought from an organic store or farmers market. Use large, plump, undamaged cloves taken from around the outside of the bulb. The smaller inner cloves usually only grow small bulbs of garlic.
Ordinary supermarket garlic, usually from China, has often been treated with preservatives that will also prevent it from growing as well as extending its marketable shelf life.
SOIL REQUIREMENTS: The soil is prepared as for onions and needs to be freely draining. A light dressing of lime prior to planting is beneficial.
SPACING: As with onions, try to imagine the final size of the bulb when planting the cloves out. A spacing of 8-10 cm is usually sufficient.
CROP CARE: It is important to keep your garlic patch well weeded. If there are too many weeds around the garlic stems they become vulnerable to fungal rot due to excessive moisture and a lack of air flow around the base of the stems. Other than that, your garlic crop should be fairly low maintenance.
HARVEST AND STORAGE: Garlic is ready to harvest when the bottom half of its leaves turn brown or yellow. In Otago, this is usually around mid-summer (February). Pull plants out of the ground and leave them to dry in the sun for a couple of days, laying them on top of the soil. Then bring them inside to a warm, dry, well aired place to complete the curing process. If you want to braid your bulbs, let the tops dry out well before doing this. Properly cured garlic can last 8 to 10 months in the right conditions.
WHEN TO PLANT: Sow seeds in trays September through to February. Seeds can be sown quite closely as the plants will only be about the width of a pencil when you plant them out and they can handle some degree of crowding. Plant out when seedlings are about 15cm tall.
SOIL REQUIREMENTS: Adding well rotted organic matter to the soil prior to planting is beneficial. Leeks are susceptible to some forms of nematode that live within the soil; companion planting with marigolds can help reduce their populations, although they are rarely a big problem regardless.
PLANTING OUT: As mentioned, plant out seedlings when they are 15-20cm tall, and space plants about 15cm apart. Leeks are usually either planted deep down inside a 'dibber hole' (a hole made with the likes of a sharpened broom handle), or else they are mounded up with dirt during their growth to 'blanch' the bottom part of the leek, encouring it to remain tightly closed and white in colour.
If planting into holes, use your dibber to make holes that are deep enough that they will leave 5-8cm of the seedling tip above the ground. After placing seedlings into the holes, water well so that the mud and dirt fills the bottom of the hole and secures the seedling in place. Further filling is unnecessary. Mulching can be good to retain moisture and prevent weeds.
WATER AND FERTILISER: Leeks need plenty of water throughout the growing season. Application of compost tea or liquid seaweed solution mid-season makes leeks continue to grow healthily and rapidly.
HARVEST AND USE: Harvest can begin at any stage as leeks are useful from scallion size onwards, although they are sweeter after their first frost. If a flower head starts to form, harvest immediatley as this forms a solid core in the leek and detracts from the flavour and texture. Leeks are an excellent crop to be harvesting over the winter and the most famous dish that is made with them is traditional leek and potato soup.
Shallots are a good option for those who are looking to grow an onion-like crop but have had troubles with normal onions. They are very tasty and easy to grow, and you can easily save a few bulbs for planting the next year. The only drawback of shallots is that they are smaller than onions and so they're a little bit more work in the kitchen.
WHEN TO PLANT: Plant shallot bulbs between the start of July and the end of September
SOIL REQUIREMENTS: The soil is prepared as for onions and needs to be freely draining. A light dressing of lime prior to planting is beneficial. Shallots can handle a slightly clumpier soil as they form pretty much on top of the soil.
GENERAL CARE: Shallots are fairly low maintenance. Keep them well watered and consider one or two applications of liquid seaweed or compost tea throughout the growing season. During the growing season you will notice the shallot plant produce multiple stems and form a clump of 5-9 bulbs. Don't worry if they're above the soil - thats how they grow.
HARVEST AND STORAGE: Somewhere around mid-summer to early-autumn the tops will start to brown off and the bulbs will look plump and mature with a papery onion-like skin. Harvest when most of the tops have started to die back. Leave to cure in the sun or a dry, drafty spot for a few days before storing in a cool, dry, dark place.
SEED SAVING: Shallots are generally propagated from bulbs, although seed is sometimes avaliable. To propagate from bulbs, simply save a few and plant em out again in July-September.