Growing onions is one of the most manageable gardening tasks, making it an excellent option for beginners. Whether planted from seed or onion sets, this versatile crop can produce juicy bulbs in just a few months. Known as Allium cepa, onions are a veg-plot favorite for their ability to thrive in small spaces and provide reliable harvests. These fleshy, rounded, underground storage organs can be used in various dishes and even stored for later use, avoiding a sudden glut. Learning how to grow onions is simple, as they share characteristics with other bulbs like daffodils, tulips, and garlic and are often planted while dormant, making them low-maintenance.
You can grow onions in autumn or spring by planting bulbs or sets. They require well-drained soil, a warm, sunny location, and watering during dry spells. Regular weeding helps maintain their health, and they adapt well to large containers if garden space is limited. The bulbs develop underground, storing energy for the plant’s growth, and their hardiness ensures success with minimal effort. Onions are perfect for gardeners seeking a mix of productivity and simplicity.
For best results, prepare the soil by ensuring it is warm, rich in nutrients, and free from weeds. With proper care, including light maintenance, like watering during dry periods, onions can yield flavorful bulbs that enhance any meal. Whether grown in small plots or spacious containers, onions are a reliable and rewarding choice for gardeners.
Choosing the right variety
Growing onions successfully starts with selecting the best varieties for your needs and growing conditions. Yellow, white, and red onions bring unique flavours—from spicy and tangy to mild and sweet—to your kitchen. Some varieties mature as early as summer, while others are ready by autumn. Certain types store particularly well and are resistant to disease or bolting, which makes them a reliable choice for long-term use. To make the process easier, many gardeners prefer onion sets, which are immature bulbs that provide the easiest and fastest crop. For extra security, heat-treated sets help reduce the risk of bolting.
Understanding your region is vital when choosing between short-day, long-day, or intermediate-day onions, as the amount of sunlight hours affects the plant’s ability to trigger bulb formation. If you prefer flexibility, seeds are often cheaper, more widely available, and offer a more excellent choice of varieties. However, they require more attention since the seedlings—the young plants—need to be handled carefully. For those planting in autumn, select varieties suited to cooler weather, as they can be harvested earlier than spring-planted sets.
The germination process is essential for starting onions from seeds. It begins with the seed coat absorbing water, causing it to expand and split, allowing oxygen to enter and kickstart growth. The embryo then uses its food reserves to grow the first root (radicle), which anchors the plant in the soil and absorbs vital nutrients and water. The first shoot (plumule) rises upwards, reaching toward the light, marking the start of a healthy plant.
Whether planting sets or starting from seeds, onions offer various options to suit any gardener. Choose wisely based on your flavour, storage, and planting season preferences to enjoy a thriving crop. With the right choice and care, your onions will reward you with reliable growth and delicious harvests.
Preparing the Soil
Preparing the soil is the first and most crucial step to successfully growing onions. Onions thrive in loose soil with good drainage, high organic matter, and a slightly acidic pH of around 6.5. If your soil’s acidity is too high, you can reduce it by adding lime in autumn or winter. For an extra nutrient boost, work in organic material, such as manure from a chicken coop or compost, which helps support healthy growth.
Choose a sunny planting site with free-draining soil, ensuring it is clear of weeds. Adding organic matter before planting is invaluable because onions have a limited root system. Mix in a bucket of garden compost or well-rotted manure for every square metre or yard of soil. This enriches the nutrients, improves the soil structure, and helps the soil hold moisture, especially during dry spells.
Properly preparing the soil creates a strong foundation for your onion plants, allowing them to grow healthy and produce a reliable harvest.
Growing Onions from seeds
Growing onions from seeds is a rewarding process that starts with careful planning and preparation. Seeds can be sown indoors or outside during mid-winter to late winter. To ensure a good crop, it is crucial to have plants growing strongly by late spring, as the lengthening days encourage bulb formation. The more leaves a plant has during this period, the larger and healthier the bulbs will become.
Sow seeds in a 2-inch-wide band and 1/4 to 1/2 inch deep when planting.
Make sure the rows are spaced 12 to 18 inches apart.
Once the seeds have sprouted, carefully thin the seedlings to maintain a 3 to 4-inch distance between plants; this spacing ensures each plant has enough room to develop strong roots and large bulbs.
Always check the seed packets for variety-specific variations, as different types of onions may require slight spacing or planting depth adjustments.
Planting Onions
Onion sets are a simple and reliable way to grow onions. In spring, plant them between mid-March and mid-April, or try specific varieties suited for autumn planting. Prepare loose soil and gently press each onion bulb into it, ensuring the neck is just below the surface. The pointed end or sprouted end should always be sticking up. Space the bulbs 4 to 5 inches apart to give them room to grow.
Protect your newly planted onion sets from birds, which may peck them out of the soil. Cover the area with fleece to prevent this until the onions have firmly rooted. Following these steps sets a strong foundation for healthy and productive onions.
Growing Onions in Containers
Growing onions in large containers is an excellent option if you lack ground space or your soil is too damp. Use a sturdy container at least 45cm (18in) wide and deep, and fill it with quality soil-based compost. Plant the sets carefully, ensuring they have enough room to grow correctly. This method allows you to enjoy fresh onions even in limited spaces.
Caring for Onions
Consistent Moisture and Fertilization
Onions have shallow roots and need a steady moisture supply to grow without interruption. Keeping the soil consistently moist ensures the bulbs enlarge correctly. For autumn-planted onions, use a nitrogen-rich fertilizer like sulphate of ammonia in late winter, or apply dry poultry manure or a general liquid fertilizer from spring to mid-summer. These fertilizers boost growth and suppress premature flowering, helping your onions thrive.
Using Mulch and Allowing Sun Exposure
Add weed-free mulch, such as grass clippings or fine mulch, to conserve moisture and prevent weeds. This also allows the tops to bask in the dry sun, which is vital for bulb development. Ensure your onions have space to grow freely without competition from weeds.
Handling Seedlings and Flower Stems
Sort seedlings by size before planting. Larger seedlings with pencil-thick diameters produce bigger bulbs, while smaller ones can be planted closer for green onions or a second crop of scallions. Remove any flower stems as soon as they appear, as they draw energy away from bulb swelling. Proper care ensures your onions are healthy, beautiful, and ready to store well after harvest.
Harvesting
Onions are ready for harvesting when their tops start falling over or turning brown, indicating the plants are mature and have stopped growing. This usually happens in late summer or early fall. While you can pull a few earlier for a good bulb, wait until the majority show these signs for a mass harvest. Avoid leaving them in wet dirt after rain, which can harm the bulbs.
On a dry, sunny day, gently tug the bulb to remove it, but be careful not to yank the leaves, which could cause damage. If the bulbs are tricky to pull, use a garden fork or shovel to wiggle around the outside of the bulb, loosening the soil without touching or damaging the onion. Leave the tops intact during this stage, as cutting them makes the onions vulnerable to bacteria during the curing process.
Storing
Let your onions layout to cure with their tops still attached to ensure they last long. Choose a warm, airy location where they can stay dry and have good air circulation. You can even sling them over a fence if they’re not rained upon. During this time, the roots will shrivel, and the necks above the bulbs will dry naturally, creating a seal that helps prevent rot. This process typically takes 7 to 10 days.
Once cured, use pruning shears to clip off the tops and roots. Carefully remove any dry dirt, but leave the papery outer skins intact. Store the onions in a cool place for best results. For sweet, juicy onions, wrapping them in newspaper or paper towels and placing them in the fridge works well to maintain their freshness.
Final Observations
Growing onions is a simple and rewarding gardening experience that suits beginners and seasoned gardeners. From selecting the right variety to planting and maintaining, onions can thrive in various conditions with proper care. They require well-prepared soil, consistent moisture, and occasional fertilization to produce robust and flavorful bulbs. Whether growing in a garden bed or containers, onions provide a reliable crop that adds value to any kitchen.
FAQs
Q- Can you grow onions from an onion?
Yes, you can grow onions by replanting the base of an onion with roots still attached, but onion sets or seeds are more effective for larger harvests.
Q- How long do onions take to grow?
Depending on the variety, onions typically take 90-120 days to grow from seeds and about 60-80 days from sets.
Q- How to grow onions from bulbs?
Plant onion sets (small bulbs) in loose, well-drained soil, ensuring the pointed end faces up and spacing them 4-5 inches apart.
Q- How do I grow a lot of onions?
Use a sunny location with fertile, well-prepared soil, space the plants properly, and provide consistent watering and fertilization for maximum yield.
