Claire Mummery: How to grow onions, the cost-effective food staple

Onions are an excellent autumn and spring planting crop. Photo / 123rf

Gardening expert Claire Mummery on the key to growing onions - which will provide you with crops for years to come.

With so many onion crops being washed away in recent floods, this is a prime time to be growing our own. I encourage you to think beyond the classic brown and red onions, as there are many different varieties of onions and, with good planning, it will mean you may never be without an onion again.

Remember - when growing any type of onion - it can seem to take forever for them to grow, but I kindly remind you that all good things take time.

It is always smart to grow a couple of long-keeping (8-9 months) varieties and, for this, I grow shallot seeds or buy shallot bulbs, and usually a long-keeping Italian variety. Both these varieties of onions store well once dried.

Growing shallots is great value for money, as they multiply, giving you 4-6 times more than you started with, and they taste deliciously sweet and juicy. The beauty of these is that, year by year, you can increase your seed stock. I like to donate a third of the harvest each year to add to my seed stock for the following year - this way, it is only ever a one-off cost of either buying seed or bulbs.

Spring onions are a great supplement when other varieties are in short supply. These can be left in the ground to get really big and harvested when needed - keep them small for salads and grow them large for cooked meals, remembering to use all of the onion including the green leaves. A top tip for spring onions is to slice the onion off just above the root and they will grow again - this time not as a single onion, but as multiples - isn’t nature just magic? Repeat sowings of these to ensure you always have onions in the gaps while you wait for the others to mature.

Little white pearls and berlotti reds are my intermediary onions, as I grow these for my everyday use and not to keep long term. If you have a small family, or are feeding just one, these are the perfect size and you never have to worry about needing to put half an onion in the fridge.

You can sow/plant the onion family in autumn or spring. Sow directly in the soil or seed trays, remembering the seeds are hard and only like to be planted in shallow drills and covered with a light soil. The key to germination is keeping the soil moist to prevent it drying out, which will only hinder germination.

When they are about 7cm high, it is advisable to thin them out into new trays to prevent attack of onion fly, as these like warm climates without airflow. Once about 10-12 cm high, plant them out in the garden, making sure they are about 6-10cm apart, depending on varieties. With my spring onions, I tend to plant in clumps for better success.

Onions like rich previous-season compost or manure with free draining soil. It’s been my observation that heavy soils tend to make root crops rot.

My top tip when transplanting is to put a nice thick mulch down first and plant through the mulch, which saves additional effort trying to mulch in between each tiny plant.

Harvest when the tops start to die down and you can see the onion bulbing out of the soil.

Onions and strawberries enhance each other’s growth and are great companions, so try to bear this in mind when sowing in autumn so that you can add strawberries to the growing bed once the weather warms up.

Happy gardening.

For more gardening advice, visit growinspired.co.nz and discover Claire Mummery’s online gardening course at www.growinspiredacademy.com