Domakihub How to Grow Onions: A Simple Guide to a Big Harvest
From soil prep to harvest, everything you need to grow flavourful onions at home in Greece.
Reviewed by Domakihub garden pros · 2026-06-23 · 5 min read
Onions are one of the most rewarding crops you can grow in a Greek garden — they thrive in the sunny, warm climate, store well through the summer, and cost almost nothing to get started. The GrowVeg masterclass above walks through the visual side of planting and bulb development; this guide takes you step by step from soil preparation through to pulling ripe bulbs. Whether you have a terrace bed at a holiday villa, a hotel kitchen garden, or a private home plot, the process is the same.
Why Grow Onions in Greece?
Greece's long, dry summers and mild winters create near-ideal conditions for onion cultivation. Bulbs bulk up best when days are long and soils are warm, which means a late-autumn or early-spring planting lets Greek gardeners time the final swelling phase to coincide with peak summer light. Local varieties such as the famous red Kytherian onion or the sweet white Skopelos onion are well adapted to the climate and worth seeking out at farmers' markets or agricultural co-ops.
For holiday rental managers and hotel teams, a productive onion bed is one of the lowest-effort kitchen-garden additions: onions need little space, almost no watering once established in the ground, and the harvest can be cured and stored for months without refrigeration.
Choosing Your Starting Method: Sets vs. Seeds
Onion sets — small, dried baby bulbs — are the easiest starting point for most gardeners. They go in the ground quickly, are resistant to bolting in cooler early-spring weather, and typically reach harvest in around 14–16 weeks. Seeds take longer (up to 20 weeks from indoor sowing) but give access to a far wider range of varieties and cost a fraction of the price per plant.
In the Greek context, sets are widely available at agronomia (agricultural supply shops) in February and March for a spring crop, and again in September for an autumn-planted crop that overwinters and bulbs up in spring. Both timings work; choose based on your schedule and how much hands-on time you want to invest.
5 Steps to Growing Onions Successfully
- 1
Prepare a Well-Drained, Fertile Bed
Onions demand loose, well-drained soil with plenty of organic matter. Dig the bed to about 25 cm, break up any clods, and mix in a generous layer of well-rotted compost or aged manure. Onions are heavy feeders early in the season but suffer in waterlogged ground — if your soil is clay-heavy, raise the bed by 15 cm or add fine grit to improve drainage. Aim for a slightly acidic to neutral pH of 6.0–7.0.
- 2
Plant at the Right Depth and Spacing
For sets, push each bulb into the soil so the tip sits just at or barely above the surface — planting too deep delays emergence and encourages rot. Space sets 10 cm apart in rows 25–30 cm apart. If starting from transplanted seedlings (grown from seed indoors), set them to the same depth they were growing at, firming the soil gently around each one. Good spacing ensures air circulation and reduces fungal disease risk.
- 3
Water Consistently in the Early Weeks
Until roots are established — roughly the first four to six weeks — keep the soil evenly moist but never soggy. Once plants are actively growing and summer heat sets in, deep, infrequent watering is preferable to daily shallow splashes; this encourages roots to go deep and makes plants more drought-tolerant. As bulbs begin to swell visibly in late spring or early summer, reduce watering gradually to harden the outer skin.
- 4
Feed and Weed Regularly
Apply a balanced granular fertiliser (high nitrogen) when plants reach about 15 cm tall to fuel leafy growth, which directly translates to bulb size. Stop feeding once you can see the bulb shoulders pushing out of the soil — nitrogen at that stage promotes lush tops at the expense of bulb quality. Weed diligently throughout, as onions have shallow root systems and compete poorly against weeds; a light hoe between rows every two weeks is usually sufficient.
- 5
Harvest, Cure, and Store
Onions are ready when roughly half the tops have fallen over naturally and the outer skin begins to paper over. Ease bulbs out of the soil with a fork on a dry, sunny day — never pull by the tops alone. Lay them in a single layer in a warm, airy spot (a shaded terrace or open shed works perfectly in the Greek summer heat) for two to three weeks to cure. Cured onions store for three to six months in a cool, dark, well-ventilated place; braiding the dried tops together is both decorative and practical for hanging storage.
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FAQ
- When is the best time to plant onions in Greece?
- There are two good windows. For a summer harvest, plant sets or transplants in February–March once the worst winter cold has passed. For an autumn-harvest crop (common in northern Greece), plant in September–October so bulbs develop over the cool, wet winter and swell in spring. Southern and island locations can often manage both timings successfully in the same year.
- Can I grow onions in pots or raised beds on a terrace?
- Yes — onions grow very well in containers at least 25 cm deep. A standard terrace planter or a fabric grow bag holds a surprisingly high density of plants. Use a quality potting mix cut with perlite for drainage, feed every two weeks with a liquid balanced fertiliser, and water more often than you would in-ground since pots dry out faster. This makes them an ideal crop for holiday villas with tiled terraces and no garden beds.
- Why are my onions bolting (sending up a flower stalk)?
- Bolting is usually triggered by a sudden cold spell followed by warming — the plant interprets this as a completed winter and rushes to set seed. Using heat-treated sets labelled 'bolt resistant' greatly reduces the risk. If a stalk does appear, snap it off immediately to redirect energy back to the bulb, then harvest those bulbs within a week or two since they will not store as well as non-bolted ones.