Guides »

How to grow onions

How to grow onions

Onions can be grown from seed, but the best results come from transplanting young plants grown in a nursery or greenhouse. You may want to start your own onion seedlings if you want to grow unusual varieties of these pungent vegetables that require more time than other vegetables to mature.

Know your climate

The most important factor affecting onion growing is climate. You can't plant onions in the winter and harvest them in the summer, so it's crucial to know your climate before you start growing them.

If you live in an area that freezes, you'll need to wait until spring to plant your onions. Onions grow best when temperatures are between 50 and 65 degrees Fahrenheit (10-18°C), but they won't tolerate frost or freezing temperatures at any point during their growth cycle; if they do get too cold, they'll stop growing and ultimately die back completely.

If you live somewhere where winters are mild enough for this not to be a concern, then go ahead and plant your onions in the fall! They can handle some light frosts here and there—it's best if you give them as much time outdoors as possible before bringing them inside for storage at about 40 degrees Fahrenheit (4°C).

Pick a suitable variety

Choosing the right variety is an important step in growing onions. If you don't pick a variety that suits your climate, soil, and drainage conditions, your onions may fail to grow properly. You should also consider whether or not you want to grow seedlings or transplants when choosing a variety—some varieties can be grown either way while others cannot. Finally, some varieties are suited better for certain growing methods than others.

In general, choose a short-day onion if you live in southern latitudes (southern California to Florida) and a long-day onion if you live farther north; these days refer to how far apart spring and fall occur on average in each location when compared with the equator (the further north/south from the equator one lives). If this doesn't make sense to you at first glance, just remember that day length increases as one goes farther north or south from the equator; therefore short-day onions will generally be more successful closer to where spring arrives earlier than fall leaves us while long-day types perform best at locations where both seasons last longer—and thus require longer days—before they begin their own transition into dormancy.

Space plants properly

Planting distance is important for onion variety, but you should also consider the size of your garden. If you have a large space, you can plant onions more closely together without worrying about them being stunted or any other issues with overcrowding. Onions don't need much room to grow, so if you have enough space in your garden and the variety will grow well in those conditions, then it's best to plant closer together than recommended by the seed packet or seedling tray tag.

Onion plants should be spaced at least 4 inches (10 cm) apart in rows that are 18–24 inches (46–61 cm) apart. This will allow ample sunlight penetration and airflow between plants; placing them too close together may result in smaller bulbs due to shading by neighboring onions bulbs as they grow taller during summertime months when temperatures rise above 80 degrees Fahrenheit (27 C).

If space allows for closer planting distances than what was mentioned above then go ahead and plant as close as possible without making sure there isn't any overcrowding on each individual plant itself since this could cause problems down the road once harvest time comes around later this year where all those tiny leaves start dying off which would lead us back into our next topic called "How To Handle Dead Leaves".

Ensure correct soil drainage

Because onions are a root vegetable, it's important to make sure that your soil has good drainage. A well-drained soil will allow the roots to breathe, which is crucial for the plant's health. If you have heavy clay or wet soils, it may be necessary to use raised beds or add more organic matter to improve drainage. If your soil drains too quickly (meaning it doesn't retain enough moisture), make sure that you don't over water them so as not to drown them!

In addition, ensure that your soil pH is somewhere between 6 and 7. Onions prefer slightly acidic conditions (like most vegetables) but can tolerate alkaline soils as well.

Temperature control

Temperature control is essential for onion production. If you are growing onions indoors or outdoors, you need to ensure that the temperature stays within a specific range. The optimum temperature for germination and growth is between 5 and 20 degrees Celsius; however, it should never exceed 20 degrees Celsius. If you are growing them indoors, your best bet is to grow them in trays filled with soil or peat moss which allows good drainage and aeration of roots.

If you are growing outdoors, make sure that the ground has been well prepared beforehand so that water does not pool up on top of it after rainfall events (this can cause fungal diseases). After sowing seeds into trenches dug out on sloping land with slopes facing northwards towards morning sunlight (if possible) where there's plenty of natural shade cover already existing at all four corners of fields will provide ideal conditions for growing healthy plants all year round without worrying too much about pests eating away at young leaves as long as they're protected by netting against birds etcetera which may damage seedlings before they've matured sufficiently!

Water appropriately

Watering is an important part of growing onions, but it's not as simple as just watering whenever the plants need it. Watering frequency and the amount of water needed depends on your climate, soil type and weather conditions.

Keep in mind that onions do not require deep waterings or frequent watering to grow well; they actually prefer to be watered infrequently. The best way to ensure that you aren't overwatering or underwatering your plants is by using a soil moisture meter (available at most home improvement stores). If you're unsure how often to water your onions, use this handy guide:

  • Soil type = clay = less than once per week
  • Soil type = sandy loam = up to once per day
  • Soil type = peaty soil = up to twice per day

Harvest at the correct time

There are several signs to look for that will tell you when your onion is ready to be harvested:

  • The leaves begin to yellow and die back, then start falling over.
  • The leaves turn brown.
  • The leaves wilt and hang low.


All in all, growing onions is a pretty simple process. It can be rewarding too as you’ll soon be enjoying a delicious batch of garden grown onions!