Onion Planting Tips

When it comes to onion planting, you want to be sure your plants are set up for success. Here are some tips to help you do just that.

Onions grow best when they receive full sun and good soil drainage. They can also be grown in partial shade.

Location

The site of an onion planting should be sunny, well-drained, fertile soil with plenty of organic matter. Avoid heavy clay soils as they retain water longer after rains.

Suitable locations include raised beds and weed-free fields. Onions like a good supply of phosphorus and potassium, so dig in a bucket of garden compost or well-rotted manure per square metre/yard before planting, to improve soil structure and hold moisture.

Plant onions in rows, 12 to 18 inches apart. Thin seedlings to four inches apart for bulb onions or two inches for green or pulling onions.

Onions will store well for several months if they are properly stored in cool, dry conditions. They are also hardy enough to be sown in late summer for an extra early crop.

Soil

Onions grow best in sandy loam soils, which are free-draining and rich in organic matter. Onions are shallow-rooted and prone to root rot if they’re too dry, so water them regularly.

Before planting, improve the soil by mixing in a good amount of aged compost or well-rotted manure per square metre/yard. Also mix in a high-potassium general fertilizer such as Vitax Q4 at a rate of one handful per square metre/yard.

Plant onion seeds 0.5 to 1 inch deep and space them 2-4 inches apart, depending on the final bulb size you’re after. Seeds can be sown directly into prepared, weed-free ground or transplanted from plug trays.

Water

Onions need consistent watering to get them started and keep them growing. They should be watered about once a week, unless it rains, and it should be just enough to moisten the top half inch of soil.

The best way to tell if onions are getting enough water is by sticking your finger in the soil next to the plants and feeling for moisture. If you can’t feel anything, they need more water.

Onions are photoperiodic, meaning they respond to daylight. Different varieties have been bred for varying day lengths, and you may need to plant them north or south of your usual growing zone.

Fertilizer

Onions are heavy feeders and need regular applications of fertilizer to grow and yield well. Fertilizers contain nutrients like nitrogen, phosphorus and potassium which can be used by the plants to produce more food.

Nitrogen is the most important nutrient for onions as it helps them develop roots and bulbs. Phosphorus and potassium are also essential, especially during the early stages of onion development.

Soil testing is the best way to determine your soil’s current nutrient levels and how much fertilizer is needed. Then you can choose the type and rate of fertilizer to provide all the nutrients that your onions need for maximum growth.

Harvest

Once onions have produced their bulbs, it’s time to harvest them. You can eat them right away or store them for future use.

The harvest should be done after the tops of the onions have wilted. This is about 90 to 120 days after planting.

To speed up the ripening process, bend the onion tops down or stomp them gently. Don’t bruise the bulb, as it can rot in storage.

Onions are photoperiodic, meaning they are sensitive to light. Different varieties are bred for varying day lengths. Long-day cultivars are adapted to Northern climates; short-day types are better suited for Southern conditions. There are also “day-neutral” (intermediate) cultivars that perform well anywhere.