These are problems people actually ran into growing onion at home, in their own words. Each answer starts with the answer. Everything here is organic — compost and homemade feeds instead of chemical fertiliser, and no synthetic pesticide — and assumes a pot on a balcony, patio or windowsill rather than a field.
Thin, yellow onion seedlings are usually starving for light or space. Onions need strong sun and room to grow, so seedlings that are too crowded or kept in shade stretch out, weaken, and lose their colour.
The fix starts with moving them somewhere they get at least six hours of direct sunlight a day—a south-facing windowsill or a bright balcony spot. If they are packed together, thin them out by snipping the weakest seedlings at soil level with scissors, leaving the strongest ones about a finger-width apart. Don’t pull, or you’ll disturb the roots of the ones you keep. Once they’ve grown enough, transplant them into a proper pot of at least eight litres, using fresh compost.
Feed with a homemade organic liquid fertiliser, like diluted compost tea or a weak seaweed soak, once every couple of weeks. Keep the soil consistently moist but not waterlogged, and make sure they stay cool—they prefer temperatures between 5 and 28°C. With more light, more space, and a gentle feed, they should green up and stand tall within a week.
Your onions are failing because their watering is inconsistent—not because of seeds, sets, or starts. Onions have shallow roots and need steady, even moisture; letting the soil dry out stops bulb growth, while keeping it soggy rots the roots, and both cause failure.
In a pot, this gets worse because the top dries fast while the lower soil stays wet. Watering a little and often only wets the surface; flooding after a dry spell shocks the roots.
Fix the routine. Use a pot with drainage holes, at least 8 liters in size. Stick your finger into the soil up to the first knuckle—if it feels dry, water slowly until water runs out the bottom; if it's damp, wait. Check it every morning. Lay a finger-thick layer of compost or shredded leaves on top of the soil to hold moisture. If the pot sits in a saucer, empty the saucer after watering.
Keep the pot in their cool growing range (5–28°C) and give it 6 hours of sun, but pull it out of harsh afternoon sun if the soil dries too fast. Consistency, not volume, is what fixes FUBAR onions.
Plant onion seeds or sets in cool weather, in a spot that gets at least 6 hours of sun, and keep the soil evenly moist but never soggy. Onions are a cool-season root crop that germinate in about 10 days and are ready to harvest around 110 days, so start early in the season when temperatures stay between 5 and 28°C.
Choose a container at least 8 liters in size if you’re growing on a patio or balcony, or prepare a loose, well-draining bed in the backyard. Use rich, compost-filled soil and plant sets about a finger’s depth apart, leaving space for bulbs to swell. Water when the top inch feels dry, and feed every couple of weeks with diluted compost tea or a liquid feed made from soaked comfrey or nettle leaves. Avoid synthetic fertilizer — too much nitrogen makes leafy tops but small bulbs.
Mulch with straw or grass clippings to hold moisture and block weeds. Stop watering once the tops flop over and begin to yellow, then lift the bulbs and cure them in a warm, dry, shaded spot for a week or two. For chives, follow the same sun and watering approach, but harvest the leaves by snipping them near the base; they’ll regrow all season.
Sow onion seeds shallowly, about half a centimetre deep, in moist seed compost, and keep the pot somewhere bright but not scorching; germination takes around 10 days. Onions are a cool-season crop, so they dislike heat above 28°C and will still germinate down to 5°C — aim for a cool windowsill or unheated room if your home is warm. Use a wide, shallow container with drainage holes, and water from below or with a fine spray so you don’t dislodge the seeds. Once seedlings appear, give them 6 hours of direct sun a day, and thin them so each has room to grow. Feed weekly with a weak compost tea or diluted homemade liquid feed once true leaves show. Keep the compost evenly moist, but never soggy — water when the top inch feels dry. Onions need a long season, around 110 days to harvest, so start early and be patient. When seedlings are sturdy, transplant them into their final pot of at least 8 litres, burying them only up to the base of the leaves.
Grow onion greens by planting onion sets or seeds close together and cutting the leaves often, never letting them form bulbs.
Onion plants put energy into bulb growth when given space and time. For greens only, you want dense planting and frequent harvesting. In a pot at least 8 liters, scatter sets or seeds about a finger-width apart, so they crowd each other and stay small. Keep the pot where it gets at least 6 hours of sun, and water whenever the top inch of soil feels dry. Feed lightly every few weeks with diluted compost tea or a sprinkle of worm castings — too much rich feed pushes leaf growth, which is what you want.
When the leaves reach finger length, snip what you need with scissors, cutting above the white base so it regrows. Continue cutting regularly; this stops bulbing and keeps tender new greens coming. In cool weather between 5–28°C, greens grow fastest. For a steady supply, sow a fresh pot every couple of weeks. If plants try to flower, cut the flower stalk off immediately to keep leaves edible.
Your onions probably didn't "take" because the seeds either cooked in too-warm potting mix or the soil dried out before germination. Onions are a cool-season root crop; they grow best between 5 and 28°C. On a hot balcony, a dark pot can heat up far past that and stop germination. They also need 6 hours of sun, but morning sun is gentler than afternoon heat in warm weather.
What to do: Sow again in cooler weather, into an 8-litre container with drainage holes. Use moist, good-quality compost and sow seeds shallowly, only lightly covering them. Keep the top inch of soil evenly damp—check with your finger—and expect seedlings in about 10 days. Once they're up, give them the sunniest cool spot you have; if the pot heats up, shade it during the hottest part of the day. Feed with a weak compost tea once established, not synthetic fertiliser. Be patient: this crop takes roughly 110 days from seed to harvest. If the first failure was in a tiny tray or shallow box, the lack of root depth is another reason they lost.
Yes, you can grow onions and Swiss chard together in the same container, as long as you give them enough space and water. Onions need at least 6 hours of sun and are a cool-season crop, so they pair well with leafy chard. In a pot, plant chard on one side and onions on the other so the onion bulbs have room to swell and the leaves don’t shade each other. Use a large container — onions alone need about 8 liters of soil, so size up for both. Water when the top inch of soil feels dry. Feed with compost or a diluted homemade compost tea every few weeks. Harvest onion bulbs around 110 days from seed, or earlier as green onions. Onions germinate in about 10 days. Avoid crowding: thin seedlings so each onion has space. If temperatures go below 5°C or above 28°C, move the container to protect it. No synthetic chemicals needed; keep pests off by hand-picking, and improve the soil with organic matter. The chard and onions won’t harm each other — go ahead and plant them together.
For cold zones, choose short-day or overwintering onion varieties and protect them, because onion's minimum temperature is 5°C, so they won't survive hard frost unprotected.
Onions are cool-season crops, but the crop facts say they only tolerate down to 5°C. That means in a cold zone you must keep them from freezing solid. Overwintering works if you sow at the right time so they establish roots before winter, then slow down and restart in spring.
Sow indoors or in a sheltered spot so germination takes its normal 10 days. Use a container of at least 8 liters, with good drainage. Place it where it gets 6 hours of sun. Before hard frost, wrap the pot in burlap or old blankets, or move it against a warm wall under an overhang. Mulch the soil surface with straw or leaves. Water when the top inch of soil is dry, but keep them on the dry side in winter to avoid rot. Feed with compost tea in early spring. Harvest 110 days after spring growth starts, or sooner for small bulbs. Choose "overwintering" or "Japanese" types if available, as they cope better with cold and re-grow quickly.
Your spring onions will not form proper bulbs, but they may swell slightly if left long enough. Spring onions are usually harvested before bulb formation; they’re picked for their tender stalks, not for a round bulb. Bulb growth is triggered by day length and temperature, and even then the variety matters — many spring onions simply stay slim.
Why it happens: in a pot, they also lack space and depth to swell. If you want to try, give them more room, keep the pot in at least 6 hours of sun, and keep the soil cool — this crop prefers cool weather, roughly between 5 and 28°C. Water regularly, but let the top inch dry out before the next watering; an 8-litre container handles that well. Feed with compost tea or a sprinkle of homemade compost to encourage growth.
What to do now: harvest the huge ones — chop and use the white base like a small bulb and the greens as scallions. If you leave a few in the pot, they may flower; let them, then collect seeds. Otherwise, eat them; huge spring onions are still good.
No — onions do not regrow after harvest. You get one bulb per plant, and once you pull it up, the plant is finished, so you need to replant new seeds or sets in fresh soil for another crop.
Onions are a single bulb crop, not a cut-and-come-again leafy green. They spend their whole growing season building that one bulb, which is why harvest takes about 110 days from seed. When you harvest, you are taking the entire plant. Nothing is left in the pot to regrow.
To get more onions, save some of your harvest to use as seed stock or buy new sets. After the first crop, refresh the potting mix by mixing in finished compost before replanting — the old soil is drained of nutrients. Onions are a cool-season crop, so replant when temperatures are within their comfortable range, and give the pot at least 6 hours of sun a day. Keep the soil consistently moist but not waterlogged, and water when the top inch feels dry. If you want a continuous supply indoors, stagger plantings every few weeks instead of expecting one plant to produce multiple harvests.
Plant one onion for every 8 liters of soil in your raised bed, so the count depends on the bed’s volume. Onion bulbs need that rooting space to swell properly—overcrowding gives small, misshapen onions and can invite rot. Measure your bed’s length, width, and depth, calculate the total soil volume in liters, then divide by 8. That gives your maximum number of plants. For a typical balcony-style raised bed, this usually means far fewer plants than you might think. Onions are cool-season crops, so keep the bed in a spot that gets at least 6 hours of sun. Work in compost before planting and feed with a homemade liquid feed every few weeks. Keep soil evenly moist but not soggy. Expect germination in about 10 days, and wait until around 110 days for harvest. If your bed is shallow or the weather gets hotter than 28°C, shade it and water more often. When in doubt, plant a little wider—healthy bulbs in loose soil beat a packed bed every time.
Look at the base of the stem: if it is flat and white like a thick wand, it's a leek; if it forms a small round bulb with the leaves coming from the top, it's a spring onion. The easiest test is to feel the lowest part of the plant just above the roots — a leek stays straight-sided and barely widens, while a spring onion swells into a little bulb. Another clue: leek leaves are flat, folded like a fan, and grow from one side; spring onion leaves are round, hollow, and bluish-green. If you planted just one seed and the plant is still young, it may be too early to tell, since spring onions can look leek-like before they bulb. Wait until the stem is at least finger-thick. If you need the bulb to form, give it the cool season and at least 6 hours of sun. For container growing, keep the pot well-watered in a pot that holds about 8 liters, and never let it go dry. Leeks can be harvested around 110 days, but spring onions come earlier. Both are edible young, so if you're unsure, just pull one and look — you'll know immediately.
Sow onion seeds in a pot of moist, well-drained compost, cover them lightly, and keep them in a cool, bright spot. That’s all germination needs.
Onion seeds sprout in about 10 days when kept in cool conditions and between 5 and 28°C. Here’s exactly what to do:
1. Fill a small pot with organic seed compost and press it down gently.
2. Scatter the seeds on the surface, spacing them a finger-width apart.
3. Cover them with a very thin layer of compost, just enough to hide them.
4. Water gently from below or with a fine mist so you don’t dislodge the seeds.
5. Keep the soil consistently moist, but not waterlogged. Put the pot somewhere with indirect light until seedlings appear.
Once the green shoots show, move the pot into direct sunlight for at least 6 hours a day. When the seedlings are sturdy enough to handle, transplant them into an 8-litre container or thin them out. Use only organic compost and water; no synthetic fertilisers are needed at this stage. Onions are a cool-season root crop, so don’t let them get too hot or dry.
For Kratky onion growing you need an 8-liter container with a lid, a net pot, one onion seedling or set, inert growing media like perlite or clay pebbles, and an organic nutrient solution.
The Kratky method works by suspending the plant so its roots dangle into a nutrient reservoir; as the onion drinks, the water level drops, creating an air gap that feeds the roots. This is why a deep, covered container and a net pot are essential — the lid holds the net pot in place and blocks light from the reservoir.
For organic feeding, fill the container with a dilute compost tea or worm-castings extract instead of synthetic hydroponic salts. Change this solution when it looks cloudy or smells off. Keep the onion where it gets at least 6 hours of sun daily, and remember onions prefer cool weather — stay within 5–28°C. Germination takes about 10 days if you start from seed, and harvest comes at roughly 110 days.
Once the onion is set, top up the reservoir only if the roots are still dry; otherwise leave the air gap alone. This passive system needs no pumps or electricity — just your container, media, and a quality organic feed.
Grow a Free Onion Garden on Your Windowsill
Grow Onions at Home: From Seeds, Sets, or Scraps to a Stored Harvest
If you haven't sown yet, the full container guide covers pot size, light, timing and what it costs versus buying it: how to grow onion at home in a pot.