Onion Plants

Take the work out of raising onions from seed with our onion plants, ready to plant straight into your patch or plot. Easy to grow and a great choice for gardeners of all experience levels, they’ll give you a generous crop of homegrown onions to pull fresh from the ground, cook with and store for later.

Onion plant FAQs


Take a look at some of the frequently asked questions we receive from those looking for onion plants for sale. You can contact our Customer Service Team or browse our general FAQs for further advice.

When should I plant onion plants?

The best time to plant onion plants is in the early spring, typically around March or April. This gives them time to establish themselves before the warmer weather arrives, which helps them develop into larger bulbs.
When growing an onion plant, you should avoid planting it too early in the winter as it might not survive the colder temperatures. Additionally, planting too late in the spring could lead to a reduced harvest. 

How do I plant onion plants?

  1. Prep your patch. Onion plants prefer an open, sunny site and light, free-draining soil. If your soil is on the heavy side, simply mix in a generous amount of grit and organic matter to help with drainage. You should avoid planting them in very heavy or freshly manured soil.
  2. Both autumn and spring varieties can go straight into your pre-prepared soil. Loosen the soil and add our Concentrated Slow-Release Feed Granules to provide essential nutrients for the best possible growth.
  3. Plant the onion plant so the tips are just poking out of the soil surface. Make sure to plant your onions 5-10cm (2-4 inches) apart, with about 25-30cm (10 inches to one foot) between each row.
    Now you can start growing an onion plant and look forward to a fantastic harvest later in the year.

How do I take care of an onion plant?

Taking care of your onion plants involves providing consistent moisture, weeding regularly, fertilising, mulching and keeping an eye out for pests and diseases.

  • Water your onions thoroughly, giving them about 1 inch of water a week, but be careful not to overwater them to avoid rot.
  • Keep the area around your onion plants weed-free. This will reduce competition for nutrients and water.
  • Apply a nitrogen-rich fertiliser every few weeks until the bulbs start to swell. Mulch with organic material to help regulate the soil temperature and retain moisture.
  • Onion plants come pre-thinned, but you should still thin out any overcrowded plants to promote airflow and reduce the risk of disease. Regularly check for pests and diseases and take action to control them if needed.

How long do onions take to grow?

Onions typically take about 3 to 4 months to be ready for harvest. As you'll be starting with onion plants, you give yourself a decent head start on this process. The time it takes them to grow can vary depending on the onion variety, growing conditions and how you planted them, but your harvest may be ready a little earlier than if you started from seed.
Harvest your onion plants when the tops start to turn yellow and fall over – it's a sure sign that they're ready to be picked.

Where can I grow onions?

Onion plants are wonderfully versatile and you can grow them in all kinds of spaces in your garden. The key is to pick a spot that gets plenty of sun and has soil that drains well. 

  • Garden beds are perfect for planting in rows or clusters.
  • Containers are great if you have limited space on a patio or balcony. Since they come as small plants, they're much easier to start in a container than seeds.
  • Raised beds provide fantastic drainage and soil aeration.
  • Growing onions among other vegetables or herbs is an excellent way to use your space and can even help keep pests away.

Why buy onion plants from Marshalls?

Your Trusted Gardening Experts

We’re more than just a team — we’re your gardening experts, here to provide trusted gardening advice, helpful guidance and expert support for all your gardening needs. Whether you’re an experienced gardener or just getting started, we’re here to help you grow with confidence.

Explore our extensive collection of gardening guides, developed from our years of gardening experience since we were founded in 1948. From growing tips and plant care advice to seasonal gardening inspiration, our resources are designed to help you get the most from your garden.

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When you order from us, you can expect a fast and reliable service. In-stock plants and seeds are dispatched within two working days, and all our packaging is recyclable, helping you make more sustainable choices for your garden and the environment.

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