Growing Onion Sets-Our Five Step Guide

Have you ever thought about growing your own onions from scratch? Perhaps some spring, shallot, pickled or red? Onions are one of those rare vegetables that are very easy to become self-sufficient with, even if you don’t have a huge amount of space. A decent sized raised bed filled with a few sets, for example, could easily produce a full years worth of onions. They are usually low maintenance, easy to grow and store relatively well. Relative is the key word as a suitably dry place to store can sometimes be a challenge with our wet Irish winters. So you want to grow onions? Just follow our five step guide and these onions won’t make you cry.

1. Preparing your Site

Onions generally prefer a less acidic, fertile soil; though they will do well almost anywhere. The soil should be firm but not too heavy and dense, if it is too heavy then you can introduce a little natural compost or manure to help retain moisture. However if its overly wet or does not get a lot of natural sun, we recommend using a raised vegetable bed to avoid disease caused by excessive dampness. Try to avoid using an excess of fresh compost matter and manure where possible, as this typically just increases the moisture content of the soil.
Before planting, the soil bed should be firmed up, either by letting it naturally occur as you allow the soil to rest and settle a few weeks before planting. Or you can speed up the process by laying slabs, planks or sleepers on the soil to help compact it down. We do this because if the soil is too loose the roots of the onions won’t be able to absorb water and nutrients efficiently, which can force them to bolt (go to seed).

2. Initial Planting

Now that your site is completely prepared, your can start sowing your sets. This is usually done around mid March to late April, but can be be earlier in a polytunnel. Typically you should plant rows about 30cm apart, and each onion set in the rows should have approximately 10cm between them. They can be done this closely as luckily they generally don’t require any thinning as they grow.
Dig a little hole, place a set in each hole with the neck facing upwards. Cover up the sets with just the very tip of the necking showing through the soil surface. If you’re unsure about which sets to plant, avoid the sets with sprouts already forming, as generally these sets wont thrive quite as well as others. Also check all sets for signs of discoloration and mould, these should be immediately discarded. By choosing only the healthiest tidy round and oval bulbs you should yield very high quality onions. To prevent birds from interfering with your crop, we recommend covering them with plant protection net for the first 4 – 5 weeks.

3. Crop Maintenance

As onions/shallots don’t have foliage to help combat weed growth, you’ll have to maintain them with regular weeding when needed. Hoeing is definitely advised too as it will help increase air and moisture circulation in the soil and encourage bulb development. Watering must be done in the morning as moisture can evaporate too rapidly during the day and doing it in the evening is too late as it may leave those bulbs sitting in excess dampness overnight while temperatures drop, which we most certainly want to avoid.
At this point lower stems should be broken off as soon as they appear, as this is a sign of bolting. Those particular onions may develop a hard stem inside the onion which can make them less suitable for storing. However they will still be perfectly acceptable for consumption of course, but should just be used as soon as possible after harvest.

4. Harvesting

So all your diligence has paid off and your crop is finally ready for harvesting. But how do we know when that is? Well as a rule, the shallots will be almost ready for harvest when about ¾ of the stems have yellowed and listed over. This typically occurs about two weeks before they are fully ready for harvesting. Once those two weeks have passed, grab a fork and lift those bulbs from the soil, taking care not to damage the skins of course as this can encourage decay and micro-organisms to attack the inner onion flesh. If possible we would recommend harvesting on a bright dry day and that you take care to clean excess soil from the bulbs as you pick them. Bulbs should then be left out to dry on a bed of soil where they can be aired out for a few days before consumption or storage.

5. Storing

But what’s the best way to store your onions? Well they generally fall into one of two categories:

  • Autumn-planted sets which will typically only store until early winter.
  • Spring-sown or planted onions which you can typically be expected to last well into the following season.

To get the greatest longevity out of your onions, whichever the situation, we recommend you first place the bulbs in a single layer on a drying rack made from chicken wire or use slatted crates placed upside-down. Use this to ripen the bulbs (in full sun outdoors if possible) for about two weeks or in a greenhouse or well-ventilated shed if the weather turns wet.

Before long they’ll be ready to place into storage, as all the foliage should be papery and dry. To do this, you should tie the bulbs into plaits, and then pop them into a few net bags or in trays in a single layer. Also make sure they’re stored in a light, cool, dry and well-ventilated place, as storing them in the dark encourages sprouting. If everything has gone to plan and your conditions are perfect, your onions could hold for an entire 10-12 months.

Shop For Onion Sets Today

You can shop our range of onion sets here. Alternatively you could try growing onions from seed here