Onion Growing Guide

Starting off on the right foot:

What are onion sets?:

Onion sets are small onion bulbs that were started from seed by growers last season then “forced” into a dormant state through exposure to cold temperatures. While you can technically start your onions from seeds yourself, the vast majority of hoby onion growers start with sets. Starting with sets offers a number of benefits: they produce a larger faster harvest and are more resilient to heat, frost, and drying out. Starting with seeds, meanwhile, means waiting two years before you can harvest or settling for harvesting smaller onions.

Selecting and preparing the planting area:

No amount of care and attention will help a plant thrive that is planted in the wrong conditions. Scout out a site that receives full sun (that means 6-8 hours of direct sunlight per day) and has rich, well-draining soil. Take a look at our article  for advice on preparing and improving your soil before planting.

Planting and caring for your onions:

When to Plant:

Onions prefer cool (however not cold) weather. For that reason, you can plant them two, four or even six weeks before your area’s last frost date, so long as your soil is workable.

How to Plant:

Just push each bulb, pointy end up, an inch or an inch and a half into the soil. Simple! Space each bulb 4 to 5 inches apart in rows 12 to 18 inches apart. Or, you could ditch the rows and plant in a grid formation with the 6 to 8 inches apart from one another on all sides.

Some gardeners like to soak their onion sets in water overnight before planting, this may encourage the sets to start sprouting faster but is not necessary.

Watering: ­­

Because onions have shallow root systems, it is important to keep the soil moist. For the same reason, frequent, lighter waterings are better than soakings. Standing water or overly wet soil can bring on disease or cause your onions to start to rot. Pay extra attention if you have poor draining soil. The best time to water is in the morning. This avoids major evaporation from mid-day sun but still allows foliage to dry out before night fall which protects against funguses and disease.

Fertilizing:

Onions are heavy feeders meaning that they need rich, nutrient dense soil to thrive and produce the best harvest. In addition to the amendments added before planting, you can also fertilize every 3 to 4 weeks throughout the growing season. A good bet is to use a well balanced fertilizer labeled as  10-10-10 or 12-12-12 fertilizer. These three-number codes refer to the proportion of nitrogen (N), phosphorus (P), and potassium (K) it contains.

–           Tip: avoid using sulphate-based fertilizers (opt for more common nitrate-based fertilizer) Nitrate based fertilizer will give the onions a sweeter, milder flavor and make them less irritating to the eyes when they are chopped.

Harvesting, curing and storing  your onions:

Harvesting:

Onions are typically ready to be harvested 40 to 60 days from planting. You can tell that they are ready once the green tops begin to die back, turn brown and/or flop over. The green tops turn brown starting with the lowest leaves. A good indicator that they are ready for harvest is that half of the leaves have turned brown while the other half are still green.

Ultimately, the only factor that determines when they should be harvested is the size of the bulbs. The simplest way to check is to brush the siol back from one to check on its size.

When you are ready to harvest, use a garden fork to gently leaver the onion bulbs out of the soil. Never pull them up. Be careful not to bruise or damage the onions in the harvesting process as this will cause them to go bad faster in those bruised areas; Handle them gently and minimize the number of times that you handle them.

To enjoy fresh onions longer, you can begin harvesting individual onions for immediate use before you are ready to harvest the whole crop. Or harvest some onions even earlier before they are really mature as green onions which are great in stir-fries and soups.

Curing:

Before they can be stored, onions need to be cured. Essentially, this process allows the bulbs to dry out. The foliage (the “necks”) will wither and the protective papery skin will dry and  tighten around the bulbs. The best conditions for cueing are warm (75-80* F), dry and well ventilated . Here’s how to do it:

• Brush off (do not wash off) excess dirt after harvesting
• Ideally, onions should be cured out of direct sunlight as this can cause them to cure unevenly
• Lay the onions out so that they are not too crowded and receive good airflow
• Sweet/mild onions should be cured for a week or less and used quickly as they do not store as well (they can be stored for around two months)
• Storage/pungent onions should be cured for two to four weeks. When the stems and roots are completely dry and the necks are dry and tight, you know that the curing process is complete.
• Trim the roots and stems away with garden shears
• Your home-grown onion supply is ready for storage!

Storing:

The type of onion you grew will determine how long they will store for. Pungent onions should store well until next year’s crop is ready. Store them in any well-ventilated container like baskets, mesh bags, or a cardboard box with extra holes punched in the sides. Keep these containers in a cool, dry, dark and well-ventilated place. Check the onions periodically for any signs of rotting and remove any offenders.

If you are feeling crafty, you can braid your onions or weave them onto a string. These storage methods are practical (ideal ventilation) and look beautiful hanging in your pantry.