If you’re trying to figure out when to plant onions in the UK, know that the best time to do so is in spring simply because onions are a cool-weather crop in its initial stages of growth. If you live in mild-winter areas, you can choose to grow onions during autumn or winter. In other words, onions grow their tops in a cooler climate while they form their bulbs when the weather’s warmer.
When To Plant Onions In the UK And UK’s Plant Hardiness Zone
The best time to plant onions in the UK depends on your area’s hardiness zone. It’s essential to know the frost dates so you can plant your seeds at the right time.
To ensure an abundant harvest, make it a point to plant your onions at least four to six weeks before the last frost. You can plant it earlier if you initially grow it indoors.
For the UK, they fall under the USDA plant hardiness zones 3 to 10. Take a closer look at the planting schedule for onions (start seeds indoors to plant seed/transplant to harvest):
- Zone 3: n/a
- Zone 4: Mid-April to Mid-September
- Zone 5: April to September
- Zone 6: Mid-March to August
- Zone 7: March to August
For more accurate information, make sure to stay updated on your local weather.
What Are Onion Sets?
Onion sets are small and dry onion bulbs grown from seed in the previous year. They harvest the onion as an immature bulb rather than allowing it to mature. These bulbs are then stored until the next planting season.
When Should Onion Sets Be Planted?
You can plant your onion sets in early spring. They’re straightforward to grow, and you can harvest them quicker since they have already started the initial growth phase.
However, it’s important to note that onion sets are limited to a few varieties. In most cases, you can only plant yellow, purple, and white onions.
How Many Onions Do You Get From One Plant?
You will only reap one onion from one bulb. Even though you can only get one onion, there are other ways you can benefit from one onion plant:
Most people are familiar with green onions (also known as scallions), the green stems that grow above the bulb. If each stem is one scallion, you can expect to harvest around 3 to 11 scallions per onion bulb.
How To Grow Bigger Onions
Here are some of the tips you should remember if you want to grow more giant onions:
Plant them early
Your onions will need all the time they can get to grow big.
Water your onions regularly
Just like most plants, it’s essential to keep your onions well-watered. The more water you give them, the plumper your onions get. So, make sure your soil stays moist.
Adding mulch around your onions will prevent weeds from growing. Otherwise, the weeds will absorb all the nutrients and water, spreading harmful diseases to your plants.
Plant them in good soil
Onions thrive best in loose, sandy loan soil. Onion bulbs that can freely expand will grow the largest. On the other hand, soil compaction restricts the growth of the onion.
Leave your onion until the tops resemble paper
Once you notice that the tops die back, please leave them in the ground for up to two weeks until they fall over. Your onions will continue to grow and absorb water, so make sure to leave them there for a few weeks.
How Many Days Does It Take For Onions To Grow?
Onions take time to mature. For scallions, they will be ready to harvest within three to four weeks after planting. For dry bulb onions, it usually takes 100 to 175 days before they mature.
Growing Onions In Mini Polytunnels
When planting crops in the UK, you need all the help you can get to reap bountiful vegetables and garden plants. As mentioned, growing big and healthy onions take time. Mini polytunnels let you extend your growing season, allowing you to grow big onions.
One of the advantages of mini-polytunnels is that it doesn’t require significant investment. It’s practical and cost-effective, especially for those who don’t want to commit to having an entire greenhouse.
Whether you’re planning to grow onion or off-season vegetables, a mini-polytunnel allows you to enjoy the benefits of growing plants that generally can’t thrive in the UK.
Here are other reasons why you should consider getting a mini polytunnel:
Control the temperature
When exposed to the elements, your plants may be subjected to extreme heat and cold. This negatively affects your onions and other plants, hampering their growth.
Placing them in an enclosed space with a controlled climate ensures that they are safe, regardless of the temperature outside. You can even add heating and ventilation systems, timers, lights, and shades.
Prevent harmful pests and diseases
Onion flies, lesser bulb flies, and botrytis are some of the pests and diseases that affect onions. These pathogens cause stress and stunt growth. Placing them in polytunnel allows your onions to focus on healthy growth rather than repair and defence.
Produce more quality onions
By keeping your onions happy and healthy, you can improve their production and growth. Limiting exposure to extreme weather conditions, pests, and diseases, you create a healthy environment for your onions to grow. This improves the quality and quantity of the onions you harvest.
Planting onions in the UK can be a pleasurable and rewarding experience if you have the right tools and resources. Mini polytunnels are suitable for any property, whether you live in a small apartment or a house with a backyard.
Now that you know when to plant onions in the UK, the next step is to consider investing in a polytunnel. If you’re looking for high-quality and affordable mini-polytunnels, Krostrade offers different options for every gardener. Check out our products today!