How to Grow Onion Sets

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While it's true all onion plants require a good, free draining soil, onion sets are not as demanding - this is especially convenient for those of us who are new to gardening and are just learning how to grow onions.

 

When you purchase your bag of onion sets empty them into a tray if you are not planting immediately and keep in a cool, light place to prevent premature sprouting. Cut off any excess dead growth from the growing tip so this doesn't become a handle for birds to pull them out of the ground.

 

Plant out your onion sets mid March to mid April... 10cm(4") apart in the row and between-row distances of 23cm(9"). Make a small hole in the soil with a trowel then pop you onion set in so the growing tip is just below the surface and firm the soil around it. Water in.

 

Keep weeds down as too much growth will affect the quality of the crop. Preferably weed by hand as onions hate having their roots disturbed.

 

Feed occasionally with a liquid fertilizer and water the onion plants if the weather is dry... but not otherwise. Apply a mulch to keep weeds down and conserve moisture; don't cover the swelling bulbs though, as they need to be exposed to the sun.

 

Cut off any flower stems that appear - you want all the plants energy going into swelling the bulb and not setting seed. Stop watering once the onions have swollen and begin to ripen.

 

Harvest main crop varieties August to September.  The onion bulb is mature when the foliage turns yellow and tips over - leave for another couple of weeks before lifting.  Choose a dry day. If the onion bulbs are ripe they can be pulled by hand but easing them out of the soil carefully with a gardening fork will ensure no damage occurs.

 

If the weather is dry and settled they can be laid on the ground on some sacking or if possible raised up a 25-30cm(10-12") onto wire netting nailed onto four posts creating a cradle. They can then be left in the garden to dry out.  If the weather is wet lay the onion plants in trays or on sacking indoors somewhere, where it is well ventilated.

 

Depending on the temperature and size of your onion bulbs - I'm sure they will be good healthy specimens by now - it will take approximately 2-4 weeks for them to dry out and cure.

 

 

 

In an effort to provide horticultural information, these educational documents are written by Nancy DuBrule-Clemente and are the property of Natureworks Horticultural Services, LLC.  You are granted permission to print/photocopy this educational information free of charge as long as you clearly show that these are Natureworks documents.