Onion ‘Karmen’ Heat Prepared (Spring Planting)

Where to Plant

Choose an open, sunny position with fertile, well-drained soil. Onions prefer neutral to alkaline conditions, so acidic soils may benefit from liming well in advance of planting. Avoid freshly manured ground and areas that stay wet, as onions don't grow well in waterlogged conditions.

When to Plant

Plant the sets from March to April, once the soil is workable. If the ground is frozen, waterlogged or particularly cold and wet, wait until conditions improve.

Planting

Plant each set with the pointed end facing upwards and the tip just showing above the soil surface. Space sets around 10–15cm apart, with 30cm between rows. Gently firm the soil around them and water after planting.

Why Heat-Prepared Sets?

These sets are heat prepared for 20 weeks to reduce the risk of bolting. Bolting is when an onion produces a flower stem prematurely instead of concentrating its energy on developing the bulb. Temperature changes and other growing stresses can still occasionally trigger flowering, so remove any flower stems that appear and use those onions first after harvesting.

Growing in Containers

You can also grow the sets in a large, well-drained container positioned in full sun. Give them enough room to develop full-sized bulbs and keep the compost evenly moist during dry weather. Container-grown onions will usually need more regular watering than those growing in the ground.

Watering & Feeding

Keep plants well watered during prolonged dry spells, particularly while the bulbs are actively developing and swelling. Once the foliage begins to yellow and fall over naturally, stop watering to allow the bulbs to mature ready for lifting.

Well-prepared fertile soil should provide a good start. On poorer soils, apply a balanced vegetable feed as growth gets underway. Avoid excessive high-nitrogen feeding, which can encourage leafy growth at the expense of bulb development.

Keep Them Weed Free

Onions have relatively shallow roots, so weeds can quickly compete for water and nutrients. Weed regularly, taking care not to damage the developing bulbs or shallow roots.

Protecting Newly Planted Sets

Birds can sometimes pull newly planted sets from the soil before they've rooted properly. Check them regularly and gently push any disturbed sets back into place. Fleece or suitable netting can be used temporarily until they're securely rooted.

Good Companions

Grow onions alongside crops such as carrots, beetroot, lettuce and other leafy salads. Their upright growth means they fit neatly into a mixed vegetable plot without taking up too much space.

Making the Most of Your Bed

Quick-growing crops such as radishes and salad leaves can be grown nearby and harvested while your onions are still developing. Just make sure the onions aren't crowded and continue to receive plenty of light.

Crop Rotation

Avoid growing onions where onions, garlic, leeks or shallots have recently been grown. These crops belong to the same plant family and can be affected by some of the same soil-borne pests and diseases.

Planning Ahead

Where possible, leave three to four years before growing onion-family crops in the same spot again. Once your onions have been lifted, the cleared ground can be used for later-sown salads and other quick-growing vegetables.

When to Harvest

Harvest once the foliage begins to yellow and naturally fall over, usually from summer into early autumn depending on planting time and growing conditions. Allow the bulbs to mature naturally rather than bending the foliage over.

How to Harvest

Choose a dry day and carefully loosen the soil beneath the bulbs with a garden fork. Lift them gently to avoid bruising or damaging any that you intend to store.

Drying Your Onions

Leave freshly lifted onions somewhere dry and airy until the foliage, necks and outer skins are thoroughly dry. In fine weather they can be dried outside; if conditions are damp, move them somewhere covered with plenty of ventilation.

Storing Your Onions

The bulbs have very good keeping qualities when properly cured. Store sound, undamaged onions somewhere cool, dry and well ventilated, using net bags or slatted trays to allow plenty of air circulation.

Top Tip

Use any damaged, thick-necked or bolted bulbs first and keep the firmest, best-ripened onions for longer storage. Check your stored crop occasionally and remove any bulbs that begin to soften.

Flavour

Expect an exceptionally sweet, mild flavour with crisp flesh. It's a particularly good choice if you prefer a red onion with less of the strong bite found in more pungent varieties.

Best Enjoyed

Slice the bulbs into salads, sandwiches, burgers and wraps to enjoy their sweetness and colourful crimson-edged rings. They're also delicious roasted or added to sauces and other cooked dishes, where the flavour becomes softer and sweeter.

Make the Most of the Colour

Serving the onion raw or only lightly cooked keeps more of those distinctive crimson-edged layers on show. Longer cooking softens both the colour and flavour.

Top Tip

For salads, slice the onion into thin rings or wedges rather than chopping it finely. You'll keep more of the attractive crimson-edged layers intact.

What to Expect When They Arrive
Your onions are supplied as dormant sets in a netted bag, ready for planting. Sets are sold by weight, so the number of individual bulbs you receive may vary slightly from the approximate count shown on our website.

Ready to Plant
Your onion sets can be planted out as soon as they arrive. Each small bulb will establish roots and grow on to produce a mature onion ready for harvesting.

If You Can't Plant Straight Away
Remove the sets from their delivery packaging and keep them in their netted bag somewhere cool, dry and well ventilated until you're ready to plant. Check them occasionally and plant as soon as conditions allow.