Watering onion plants successfully can be tricky. Too much or too little can cause problems. Before you choose the best way to water your onions, you should learn about how much water they need.
When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works.
Onion plant watering can be a tricky business. The bulbs will not grow as big or as well if they don’t get enough water. If they get too much water, fungi can get into the plants and cause them to rot. You can water onions in a few different ways, so it’s helpful to learn about how onions should be watered in general before choosing the best way to water them for you.
Onions need a lot of water, but the soil should never get soggy. Ideal onion water needs are to irrigate to a depth of an inch (2. 5 cm. ) once a week rather than a light sprinkling each day.
If you use a hose or sprinkler to water your onions, do it in the morning instead of the middle of the day when the water will soak away.
Overhead watering can spell trouble. If you water in the evening, the foliage will stay wet overnight, which can foster disease. There are two other onion plant watering methods, though, that can alleviate the problem with wet foliage.
Onions are a popular vegetable to grow in home gardens. With their pungent flavor onions can elevate any dish. However growing tasty, large onions requires paying close attention to irrigation. Knowing how much water onions need and when they need it is crucial.
Onion Growth Stages and Water Needs
Onions go through three growth stages, each with different watering needs:
Onion Seedling Stage
- Lasts approximately 45-60 days after seeds are planted
- Seedlings need consistent moisture in the top 6 inches of soil
- Water 1 inch per week during this stage
Onion Bulb Formation Stage
- Lasts approximately 45-60 days after the seedling stage
- This is when the onion bulb begins to form and expand
- Water needs increase to 2 inches per week
Onion Maturation Stage
- Lasts approximately 15-30 days before harvest
- Watering can be decreased to 1.5 inches per week
- Stop watering completely 1-2 weeks before harvesting
General Onion Watering Guidelines
- Space onion plants 4-6 inches apart in rows 1-2 feet apart
- Plant onions 1/2 inch deep
- Onions need approximately 1 inch of water per week
- Water deeply and infrequently, about once a week
- Water at soil level, avoid overhead watering
- Stop watering once onion tops start to fall over, about 2 weeks before harvesting
How Often Should You Water Onions?
-
Water onions about once per week, providing 1 inch of water
-
Adjust frequency based on soil type. weather and growth stage
-
Sandy soils will require more frequent watering than clay soils
-
Hot, dry weather increases water needs
-
More water is needed during bulb formation stage
-
Stick your finger 1 inch into the soil to check moisture before watering
-
If soil is dry, it’s time to water
Watering Methods for Onions
There are several methods to properly irrigate onions:
Hand Watering
- Use a hose or watering can to manually water onions
- Water at soil level, avoid overhead watering which can promote diseases
- Water in morning so foliage dries quicker
Drip Irrigation
- Most efficient method, provides water directly to roots
- Use drip tape buried 2-4 inches deep, with emitters every 12 inches
- Moisture is consistent with less water lost to evaporation
Furrow Irrigation
- Channels or furrows are dug between onion rows
- Furrows are flooded with 1-2 inches of water, allowing it to soak into soil
- Avoids wetting onion foliage, reducing disease risk
Sprinkler Irrigation
- Set up sprinklers or impact sprinkler heads between onion rows
- Water early in day so foliage dries quickly, avoiding fungal issues
- May be less efficient than drip or furrow irrigation
How Much Water Do Onions Need in Total?
Onions are relatively high water users. Total water needs depend on climate and onion variety.
- Short-day onions need approximately 18-24 inches of water total per season
- Long-day onions need approximately 24-30 inches of water total
Track rainfall and irrigation amounts to ensure onions are getting adequate water through each growth stage.
Signs Onions Need More Water
Watch for these signs your onions may be under-watered:
-
Soil is dry 1 inch below surface
-
Onion tops appear shiny, curled or wilted
-
Stunted onion growth
-
Small onion bulbs
-
Pale or yellowed onion leaves
Signs Onions Are Getting Too Much Water
These are signs your onions may be getting over-watered:
-
Soil is soggy or stays wet for days after watering
-
Soft onion bulbs
-
Mushy roots or root rot
-
Fungal leaf diseases like downy mildew or botrytis
-
Onion bulbs with delayed maturity, thick necks
Best Practices for Watering Onions
Follow these tips for success in irrigating onions:
-
Choose well-draining soil and raised beds if possible
-
Mulch around onions to retain soil moisture
-
Irrigate based on soil moisture, not on a fixed schedule
-
Water thoroughly, moisture should penetrate 6-12 inches deep
-
Avoid overhead watering methods that wet foliage
-
Stop watering once tops start falling over before harvest
-
Provide supplemental water during dry spells
Proper onion irrigation, adapted to your soil and climate, will result in the best yields of large, flavorful bulbs. Pay close attention to onion growth stages, monitor soil moisture, and adjust your watering schedule accordingly. With good moisture management, you can enjoy lush, healthy onion plants.
Frequency of Entities:
onion: 44
water: 38
inches: 12
soil: 11
irrigation: 7
bulbs: 6
row: 5
foliage: 4
drip: 4
weeks: 4
moisture: 4
needs: 4
growing: 4
furrow: 3
overhead: 3
disease: 3
roots: 3
irrigate: 3
emitters: 2
evaporation: 2
rainfall: 2
raised beds: 2
stop: 2
mulch: 2
supplemental: 1
shiny: 1
curled: 1
stunted: 1
pale: 1
yellowed: 1
soggy: 1
wet: 1
soft: 1
mushy: 1
rot: 1
downy mildew: 1
botrytis: 1
delayed: 1
maturity: 1
necks: 1
thoroughly: 1
penetrate: 1
adapted: 1
flavorful: 1
yields: 1
growth stages: 1
monitor: 1
adjust: 1
schedule: 1
lush: 1
healthy: 1
management: 1
enjoy: 1
Gardening tips, videos, info and more delivered right to your inbox!
Now is the time to sign up for the Gardening Know How newsletter and get our most popular eBook, “How to Grow Delicious Tomatoes,” for free. “Please send me news and deals from other Future brands. I also agree to receive emails from us on behalf of our sponsors and trusted partners.”
Place the tape 3 to 4 inches (8 to 10 cm) deep in the middle of the onion bed between rows. ) with emitter spacing about a foot (31 cm. ) between emitters. Water occasionally and deeply; provide an inch (2. 5 cm. ) of water at each onion watering.
To tell if the plants have enough water, stick your finger in the ground next to the plants. If you can’t feel any moisture up to your first knuckle, it’s onion watering time.
How to Irrigate Onions
Besides using a hose or sprinkler, furrow irrigation and onion drip irrigation are two other ways to water onion plants.
Furrow irrigation is just what it sounds like. Furrows are dug along the length of the onion row and flooded with water. This allows the plants to slowly soak up the water.
A drip tape, which is just tape with holes punched in it, is used for onion drip irrigation. The holes in the tape send water directly to the roots of the plants. This method for watering onions eliminates the issue of fungal disease that can result from overhead watering.
How Often to Water Onions for Perfect Growth?
FAQ
Do onions need to be watered a lot?
How much water does an onion plant need per day?
When should I stop watering onions?
How much water do onions need?
I find that watering onions at the correct time is as important as how much to water. Generally, onions need 1 inch of water per week, but I check the soil moisture using a moisture meter to be precise. I recommend watering early in the morning or late in the afternoon to reduce evaporation.
How do you water an onion plant?
Install the tape in the center of the onion bed between rows at a depth of 3 to 4 inches (8-10 cm.) with emitter spacing about a foot (31 cm.) between emitters. Water occasionally and deeply; provide an inch (2.5 cm.) of water at each onion watering. To tell if the plants have enough water, stick your finger in the ground next to the plants.
How often should I water my onion garden?
A good watering session can sustain your onions for up to a week, especially in wet or cool temperatures. Be mindful not to give your plants too much water, as it can lead to disease and affect the overall health of your garden. When tending to your onion garden, understanding the balance of moisture needed can enhance the quality of your crop.
Should you water onions before harvesting?
Overwatering is equally problematic. If leaves develop a yellow tinge, cut back on watering. The closer to harvest time, the greater the need for water, but watch the plants carefully—when the onion tops start falling over, stop watering and let the soil dry out before harvesting.