Onion ‘Rosanna’ Heat Prepared (Spring Planting)

Where to Plant

Plant Onion ‘Rosanna’ in an open, sunny position with fertile, moisture-retentive but well-drained soil. Before planting, remove weeds and work in well-rotted garden compost if needed. Avoid freshly manured ground and soil that stays wet, as onions can rot in waterlogged conditions.

When to Plant

Plant ‘Rosanna’ sets from March to April, once the soil is workable. If the ground is frozen, waterlogged or particularly cold and wet, wait for conditions to improve before planting.

Planting

Plant each set with the pointed end facing upwards and the tip just showing above the soil surface. Space sets around 10cm apart, with 25–30cm between rows. Gently firm the soil around them and water after planting.

Why Heat-Prepared Sets?

‘Rosanna’ 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 putting its energy into the developing onion. 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

‘Rosanna’ can also be grown in a large, well-drained container. Give the sets enough room to develop full-sized onions 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

Once established, onions generally only need additional watering during prolonged dry spells. Keep them well watered in dry weather while the bulbs are actively developing and swelling, as a lack of moisture at this stage can limit their final size. As the crop reaches maturity and the foliage begins to yellow and fall over naturally, stop watering to allow the bulbs to mature ready for lifting.

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

Keep Them Weed Free

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

Protecting Newly Planted Sets

Birds can sometimes pull newly planted onion 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 the sets are 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

‘Rosanna’ is generally ready to harvest from August into September, depending on planting time and growing conditions. The onions are ready to lift once the foliage begins to turn yellow and naturally fall over.

How to Harvest

Choose a dry day and carefully loosen the soil beneath the onions with a garden fork. Lift them gently to avoid bruising or damage.

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.

After Harvesting

Once thoroughly dried, keep sound, undamaged onions somewhere cool, dry and well ventilated. Check them regularly and use any damaged or softening onions first.

Top Tip

If any plants produce a flower stem despite the heat treatment, mark those onions and use them first after harvesting rather than keeping them for later.

Flavour

‘Rosanna’ has a sweet, fruity and mild flavour, with less pungency than many onions. Slice through it and you'll also reveal the distinctive rosy-pink rings running through its crisp flesh.

Best Enjoyed

Its mild flavour makes ‘Rosanna’ particularly good thinly sliced into salads and sandwiches, where you can enjoy it raw without overwhelming the other ingredients. Cooking brings out its natural sweetness in sauces, casseroles, soups and roasts.

Make the Most of Your Crop

Enjoy freshly harvested onions raw while their crisp texture and distinctive colour are at their best, then use the remainder for everyday cooking as you work through your harvest.

Top Tip

Slice ‘Rosanna’ into thin rings rather than chopping it when serving raw. This keeps more of its distinctive pink-ringed appearance on show.

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.