When to plant onions?


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Onion Growing and Harvest Information

Germination 50-85F
For Growth 55-75 F
Soil and Water
Fertilizer Light feeder, use compost
pH 6.0-7.5
Water average
Planting depth
– seed 1/2″
– set 1″
Root depth 18″ – 3′
Height 15-36″
Width 6-18″
Space between plants
scallions 1″
Bulbs 3″
Average plants per person 40
Wait until the tops fall over; pushing them can shorten shelf life. When bulbs pull out very easily, rest them on the ground to dry and cure. Treat gently as they bruise easily. Turn once or twice in the next few days; cover if it rains. When completely brown, they’re ready for further curing. For regular onions, clip the tops 1″ from the bulb. Do not clip tops of multipliers or separate bulbs. Spread onions no more than 3″ deep on wire screens in a shady, warm, well-ventilated area. Cure for up to 2 months before storing for the winter. The flavor and quality of multipliers keeps improving. After 2 months, check for spoilage and remove bad or marginal onions. Separate multiplier bulbs by cleaning and cutting off dried tops about 1″ above bulbs. Keep the smallest bulbs for spring planting.
First Seed starting Date 46-92 days before last frost date
Companions lettuce, pepper, spinach, strawberry, tomato
Incompatibles All beans, asparagus, peas, sage

Onions are easy to grow, have a fairly short growing period and take up little space in the garden. If you don’t have a vegetable garden, plant a few onions in your flower garden or in a pot or box and set them on your patio or in a sunny window. For an easy perennial onion patch, grow potato onions. Almost a lost variety, with flavor stronger then shallots, they can substitute for regular onions. Buy them once, plant in fall or spring, and enjoy harvests for decades.

Where to Grow Onions

Onions are a cool-season crop, hardy to frost and light freezes, although certain varieties are exceptions. They can be grown practically everywhere, and prefer a cool- season start. Onions are as hardy as they come. Frosts, freezing temperatures and snow will not kill them. They should have steadily moist soil and even growing weather to mature at a steady pace. Otherwise they bolt to seed or do not form good bulbs. High temperatures and low humidity are advantageous during bulbing and curing.

Recommended Varieties of Onions

Common Slicing Varieties: White, Yellow or Spanish Onion (most commonly used)
– Vidalia Onions – good sweet onion to cook with, look for Walla-Walla, Vidalia onions are trademarked and only grown in the state of Georgia.
– Red Onion – known for it’s sweet taste, often eaten raw on salads, looks purple
– Scallions or Green Onions – grown for it’s long stem, has little or no bulb
– Pearl Onions – for pickling
– Shallots – mild tasting, small bulb, more expensive than other onion varieties
– Leeks – mild tasting stalk
– Chives – onion flavored herb, usually used on salads or as a garnish
Note: Home grown onions have a much stronger flavor than store bought onions.

Multiplier onions, such as shallots and perennial potato onions reproduce vegetatively and are usually started by sets. Similarly, bunching onions, such as scallions, Welsh and Japanese, don’t form full bulbs and are usually started by sets. Sets should be started with small bulbs no larger than 3/8 to 7/8 inches. Sweet onions are best started from seed, as is the common or regular onion.
What’s the difference between Long and Short Day Bulbs?
Most onion varieties begin to form a bulb when the temperature and hours of daylight reach certain levels.
Long Day Bulbs, for northern latitudes, begin to bulb when there is 14-16 hours of daylight.
Short Day Bulbs, for southern latitudes, begin to bulb when there is 12-14 hours of daylight.

Soil for Onion Growing

A fertile, mellow soil, well enriched with compost and rotted manures. The ground should be free of pebbles and stones and moisture retentive. Since onions are shallow rooted and need constant moisture to develop well, a well-balanced fertilizer should be worked in before planting. Onion growth and yield can be greatly enhanced by banding a fertilizer rich in phosphorous (10-20-10) 2-3″ below transplants at planting time. Make a trench in the center of the bed 4″ deep and distribute 1/2 cup of fertilizer per 10′ of row. Cover the fertilizer with 2″ of soil and plant onions 6″ from the trench on either side, don’t plant onions in the trench. Plant onions in a sunny location with good drainage and always keep the soil moist.

Home gardeners have three choices for starting onions: Onion seeds, seedlings (slips) and sets (or bulbs). Seeds take the longest time and should be started indoors, but are the cheapest. Slips give you a head start on growing and are hardy. Onions started from seeds generally grow larger and store longer, while sets are easier and faster to grow, but are more subject to bolting and rot.

When –

Onions are relatively hardy, so planting can begin as soon as the soil is dried out and workable in spring. In milder climates( >zone 8), they can be planted in fall for spring harvest. If planted in too cool weather, onions will not form bulbs. Onions can be planted as soon as the garden can be tilled in the spring, usually late March or early April in prime growing regions. Good fertility, adequate soil moisture and cool temperatures aid development.

How –

Plant onions 1 inch deep and 3 to 4 inches apart in double rows, leaving 6 to 10 inches between rows. Be sure to leave enough room between rows to weed. If the onions are planted closer together, you can harvest every other plant as a green onion so that bulb development of the remaining plants is not impeded.

How Onions Grow

The onion is a bulb-forming plant with long, tubular, deep, rich green leaves. They vary in size from the tiny green or spring onions to the large sweet Bermuda-type onion. Colors are white, yellow, and red. Bulb onions mature in response to changing amounts of daylight. The longer the plants grow before forming bulbs, the bigger and better those bulbs will be. In North America, days become shorter after the summer solstice (June 21st). Summer days are longer in the North than in the South, which is the determining factor in choosing the best plants for your area. Be sure to chose short day, intermediate day, or long day based on your latitude for the best onions. Buying from a local reputable dealer, or a legitimate supplier should offer some guidance to help you choose.

Cultivating Onions

Onions have shallow roots and compete poorly with weeds and grasses. Timely shallow hoeing and cultivation are important, especially when the onions are small. Onions need fertile moist ground. Side-dress with fertilizer rich in nitrogen every 2 to 3 weeks and water well in any dry spells. It is important to stop fertilizing within 3 weeks of harvest when the necks begin to feel soft.

Storage Requirements
Onions sprout in the presence of ethylene gas, so never store with apples, apricots, avocados, bananas, figs, kiwis, melons, peaches, pears, plums, and tomatoes. Eat the largest ones first. They are the most likely to sprout.
Temperature Humidity Storage Life
36-40 F 65-70 % 1-8 months (dry)
Method Taste Shelf Life
Canned good 12+ months
Frozen fair 3 months
Dried good 12 months

Onions are ready to harvest approximatly 150 days after planting seeds, and approximately 100 days after transplanting sets. Green or spring onions are pulled as needed when the stems are about 1/4 inch thick.
Pull green onions anytime after the tops are 6 inches tall. Green onions become stronger in flavor with age and increasing size. They may be used for cooking when they are too strong to eat raw. Sweet onions generally store poorly, whereas pungent varieties store well because of a high content of aromatics, which act as preservatives.
Remove any plants that have formed flower stalks and use immediately. They do not produce good bulbs for dry storage.
For dry onions, those that will be dug and stored, the tops will start to yellow off and fall as the bulbs are maturing probably late July or early August, as can be seen in the nearby image. If the entire row does not ripen uniformly, when the majority of onions are ripe, knock down the foliage of the others with the back of a rake. Dig the onions carefully and allow them to dry in the open sun for a few days. Rinse off the dirt and allow the onions to dry with the tops still attached in the open air for about 2-3 weeks. Then, cut the tops and roots off of the onion, and allow the cuts to air dry for two or three days. This will help to seal the onion and avoid premature spoiling. Store in a porous or net bag in a cool, dry place.
To keep mature onions for a longer period of time, lay them in a single layer on newspaper in a warm, well ventilated place to cure for 2-3 weeks. Leave undisturbed until the outer skin becomes papery and crispy dry. Select unbruised onions, rub off the stringy roots and braid the tops. Braid and hang them in bunches or place in mesh bags and hang away from moisture. If onions are stored in a cool dry place (50 to 60 degrees), they will keep for 6-8 months.

To store scallions or green onions, place them in a jar or vase and put some water in the bottom. You can continue to cut the tips as they grow, and they won’t spoil for quite some time.

Onion Pests

– Thrips – Keep areas near onions mowed to reduce the weedy habitat that onion thrips prefer.
– Onion maggot – Be alert for flies in spring. The adult flies are attracted to rotting onion tissue, so rotate onions with other crops, and compost all refuse after harvesting.

Onion Diseases

The onion family is resistant to most disease, although wet and humid weather can increase the likelihood of disease. Most members of the onion family are resistant to insect problems; however, above 40 degrees north latitude, root maggots may attack the roots of onion plants. Insecticidal soap sprays are very effective should you have a problem. Onions and garlic are ingredients in a number of organic insect sprays. Buy quality sets and plants to be sure of clean stock.

Why do onions make you cry?

When you cut into an onion, the cell walls are damaged releasing a sulfur compound called propanethial-S-oxide which floats into the air. This compound is converted into sulfuric acid when it comes in contact with water which is why it stings your eyes. Chilling inactivates the propanethial-S-oxide so it does not float into the air. Thus, no tears.
To keep eyes dry when chopping onions, try chilling peeled onions in the refrigerator before chopping. To get the onion smell off of your hands, rub with lemon juice or vinegar. To freshen onion breath, chew a little parsley or a coffee bean.

Other bulb plants for the garden similar to onions:


Garlic is simple enough to grow. Simply pull apart a garlic bulb, and plant the individual cloves about 2 inches deep and about 2 inches apart. Mature garlic bulbs should be ready in 3 months.
Shallots are highly prized by French chefs and can be difficult to find year round in your local market. They tend to be expensive, and are as simple to grow as garlic. The flavor reflects the quality of the soil, however, and since bitter taste seems to follow planting in clay soil, use typical good onion soil for shallots. The tops will start to brown off and yellow when the bulbs are mature, in about 90-110 days.
Unless noted otherwise below, leeks have the same needs as onions. Varieties are Broad London (Large American Flag); Swiss Special; Conqueror. Seed is usually sown indoors about 2 months before planting but can be seeded directly outdoors. Germination is in 10 days. Seedlings are set in a 6 inch trench, in rows 2 feet apart, with 6 inches between sets. The object of the trench is to blanch the leeks white as they grow; the row is gradually filled in as the leeks develop or the soil is merely hilled around the plants as they near maturity; but be careful not to brush soil into the leaf stalks. Leeks should be pulled when fully mature, about an inch in diameter, in 120-130 days. In mild climates they can be left in the ground over winter and dug as needed. But in colder climates, they should be harvested before frost, although some gardeners have been successful in mulching leeks heavily and harvesting all winter.


Free set of Onion Bulbs!

Find your coupon at the end of this article.

Growing your own spuds and onions is easier than you might think.

If you think you love French fries, wait ‘til you taste fries made from your own home-grown potatoes! Maybe you prefer hash browns…. or tiny new potatoes in cream sauce with parsley… or pan-fried potatoes with roasted red papers and onions! You get the idea. I’m a spud-lovin’ kind of girl. So it’s great that with just a little T.L.C., those beautiful potatoes can be thriving in your garden or mine.

The best time to plant potatoes is at least four along the Front Range is at least four weeks before Mother’s Day, so the timing now is purr-fect!

Tagawa Gardens’ spud department is open for business!

Your potato crop needs to start with “seed” potatoes. These are very young potatoes grown specifically to be used for planting, not eating. Potatoes from the grocery store are routinely treated to prevent sprouting. They’re not what you want in your potato bed.

Tagawa’s bulk seed potato selection includes the always popular, rich and buttery Yukon Gold. We also have Kennebec and Red Pontiac in bulk.

For organic gardeners, Tagawa’s carries a variety of seed potatoes, including Rose Finn Apple, French Fingerling and Purple Majesty.

Seed potatoes about the size of a golf ball are ideal. Larger potatoes can be cut in half. Let the cut ends air dry at least overnight indoors to create a skin… a seal again infection before they’re planted.

Be sure that each “seed” has at least two “eyes” or buds. That’s where the tubers will sprout and send up shoots.

Good soil comes first

Colorado is one of the top potato-producing states in the country. But odds are, the soil in the potato fields of the San Luis Valley in western Colorado has a pretty good head start on our Front Range gardens, so let’s work on that.

Potatoes will rot in soggy, poorly-drained soil. Two to three inches of high-quality compost worked into the potato patch before you plant can make a huge difference. Be sure to locate your potato bed where the plants will get at least six hours of bright sun every day.

Dig a trench about four inches deep. Mix your compost and some well-balanced plant food into the loosened soil at the bottom of the trench.

Tagawa Gardens is proud to offer Nature’s Yield® compost. Popular fertilizers include Espoma® Garden Tone for organic gardeners or Grow Rich® lawn food by Richlawn. The Age Old® Organics line of fertilizers work well as supplements later in the season, too.

Planting and watering

Tuck your seed pieces into the loosened soil at the bottom of the trench, setting them about 18 inches apart in rows two feet apart. The “eyes” should be facing up. Cover them with a few inches of compost-enriched soil and water them well. Take note: Never let your potatoes dry out! They like moisture, but they hate soggy soil. Give them occasional deep soakings. Check the trench after you water until you get the hang of it.

Grow and cover…. cover and grow

As the potato vines emerge, keep gently adding soil over the plants, a few inches at a time, always leaving part of the vine exposed. When the vines have grown taller than the trench, mound one last time, creating a slight hill.

With good sunshine and proper watering, your spuds should be ready to harvest in the fall, about two weeks after the first frost kills their foliage. And then, bring on the hash browns!

Want some onions with those hash browns?

You’re in luck! Spring is onion-planting time, too!

I think onions are one of the easiest garden crops of all. Like potatoes, they do best in soil well-amended with compost. Beds should get at least six hours of full sun daily.

Onion “sets” look like miniature onions. Tagawa Gardens sell top-quality sets for red, yellow or white onions. The sets should be just barely tucked into loosened soil, with their tips no more than 1½” below the soil surface. Place the sets about four inches apart in rows a foot apart.

A little extra water

Because the roots of the onion plants are so close to the soil surface, they dry out quickly. Water the onions well when you first plant them. Keep watering throughout the season as the top layer of soil dries out. Applying water at the soil line rather than from overhead will help to avoid disease. Feed with a 5-10-5 fertilizer at the recommended rate once a month during the growing season.

Onions don’t compete well with weeds. A loose layer of mulch like straw around your onion plants can keep the weeds down and conserve moisture.

By mid- to late summer, the leaves of the onion plants will start to yellow and shut down. Their job is done. Withhold water as the necks or stems of the onions bend over and lay down. Let the onions “rest” in place for a couple of weeks, then gently pull them out of the ground and finish curing them in a well-ventilated area.

As soon as your potato crop is in, it’s time for hash browns with onions. Which means I’ll be right there! Have fun!

Get Your Free Pack of Onion Bulbs!

to plant other early season vegetables such as bare-root asparagus and seeds for root vegetables such as carrots and beets and radishes. See our video below.

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Multiplier Onion Sets


Plant seed as soon as the soil can be worked in the spring. Onion seed germinates in a wide range of soil temperature, 18-29 degrees C. Sow and cover seed with 1⁄2 inches of soil; keep moist. Onion seeds started indoors 6-8 weeks ahead of transplanting will be earlier, larger and have a better shape than sets and direct seeded onions. Plant 3-4 seeds in a1 inch cell. Thin to 2 seedlings per cell. Seedlings can be trimmed to 3-4 inches in height to promote stockier transplants. Thin or transplant to 3-4 inches apart in rows 18-24 inches apart. To plant onion sets, simply press sets into the soil about 2 inches apart. Later thin to about 4-6 inches apart to allow bulbs to mature. Bunching onions can be left at 1-11⁄2 inches apart. Space shallots 1 inch apart in rows 4 inches apart.


Onions benefit from full sun, soil pH of 6.0-7.5 and a well-drained soil with plenty of compost or well-rotted manure added. Feed with a complete balanced fertilizer during the growing season, particularly when the bulbs start to form.


Bunching onions are used when young and green. To harvest storage onions: when onion tops begin to fall over, turn brown and wither, it is time to harvest. Tipping bulbs over to break some of the roots will speed drying. Pull and place onions in dry, warm airy location out of direct sun for up to 3 weeks to cure. After curing process is complete, store in cool, dry location. The drier the onions, the better they store.

Pests & Diseases:

Storage rot may be the result of diseases encountered during the growing season. Onions should be cured before storing.


Beet, cabbage family, carrot, kohlrabi, lettuce, parsnip, pepper, spinach, strawberry, tomato, turnip.

Onions are some of the easiest things to grow and require very little looking after. As our friend Dermot Carey (last head gardener of Lissadell House) says if you can’t grow onions you might as well hang up your gardening gloves and take up golf.
Now, Dermot is a professional vegetable gardener and while I agree onions are an easy crop there are a couple of things worth looking out for to make sure you get a successful harvest. Most of us will know you can either grow onions from ‘sets’ or seeds so here’s a little information on both:

Onion Sets
Onion sets are just immature or part grown onion bulbs from the previous year. They are produced by sowing onion seed very thickly which results in plants with very small bulbs. These little onions are sown the following spring to mature and produce full grown onions.

Sets are the easiest way for the beginner to grow this essential crop as they are so easy and pleasurable to set out. You won’t get as wide a choice of varieties but you will have a greater chance of success.

When to sow onion sets
The best time to sow onion sets is mid March to mid April. If you are sowing red onion sets is better to leave them till April as they are more prone to bolting and a later planting may help.

Sets can also be sown in Autumn from September to early October. If you have a wet garden or live in an area of high winter rainfall growing in raised beds is recommended as sets left in wet soil are likely to rot.

You can also plant sets in modular trays which can be kept in an unheated greenhouse or tunnel for planting out when the weather allows from mid March.

Site and Soil
Onions like an open sunny site. Your soil should be fertile with a good bucket or two of well rotted garden compost raked into the surface layer as onions have relatively small and shallow root systems. Avoid manure or high nitrogen feeds as this can result in thick necks which won’t try properly and will rot from the inside out.

If you are looking for a good soil amendment before planting onions I can happily recommend ‘Envirogrind‘ soil improver which I use every year, I just spread it on the surface of my beds and cover with the ‘Growgrid’ onion planting mat I mention below.

Sowing Onion Sets
Once you have your bag of little golden onion sets you’ll have to pick the best ones to sow. This is very important, if you’re doing your job properly you’ll end up throwing half of them out so bear that in mind when you’re ordering. Here’s a quick diagram to help you pick the best.

From left to right:

  1. You don’t want any shoots, you might think you’re getting a head start but you’ll just get a very poor quality bulb.
  2. Avoid any skinny looking ones.
  3. Discard anything with mould or brown patches on the skin.
  4. Any very big sets are more likely to run to seed.
  5. Now, that’s the fella. Nice, tidy and round, will produce a perfect onion.

Planting (If you have any left after sorting them…..)
Push the sets about 1 cm into loose soil approx 10cm apart, leave about half of the onion showing above the soil. Birds seem to love pulling your handiwork out of the ground and scattering them round the garden. You can solve this by placing enviromesh or cloches over them till they get going.

If you want to be clever and save weeding later on you can plant through a sheet of black plastic. Spread the plastic over your prepared bed, make a hole just large enough for each set and just pop them in. We stock ‘Growgrid’ onion planting mats which are a ready made version with pre cut holes. I use them every year and find excellent.

The mats have a grid of heat sealed holes spaced at 15cm intervals which is perfect for growing medium to large sized onions. The heat sealing is the trick and prevents the mat from unravelling. I have been using the same mat for the last 4 years and it is still going strong, it is one of the best value items in my garden.

Sowing Onion Seeds
You have a much better choice of variety when you grow from seed but you need to start off much earlier in the year. You will need a greenhouse and heat bench to get them going as you’re sowing late January to February.

The best way is to sow 4 seeds per cell in a modular tray. You can move the tray from the heat bench around mid march but keep inside till early April when you can begin hardening off. Put your trays out on days without frost but back in again at night. You can plant them in their final positions in early May (Late April if not too cold) spacing them in a staggered pattern 30 x 30cm apart.

Spring Onion
I never had much success with spring onions until I tried Ishikura. Most people, including me struggle with the popular ‘White Lisbon’ which produces a weedy looking result. You will get a scallion much more like the larger crunchy variety you’re used to in the shops with my new best friend, Ishikura Bunching.

You can sow them from late march in a greenhouse and continue outside until July. We find the easiest way of growing them is in modular trays. Sow 8-10 seeds in each module and plant the whole lot out 4 weeks later. There is no need to separate them making it easy to harvest a bunch at a time when you need them.

Your scallions will be ready to pick 8 to 10 weeks after sowing and don’t last long once ready. It’s best to sow a new lot every 2 weeks or so.

Onion Problems
The most common headache you’ll have in Ireland is downy mildew. This is because of our damp climate and why we recommend ‘Santero’ and ‘Golden Bear’ which have resistance to it. To try to avoid it keep your onion bed weed free with plenty of air circulation. If you have a wet garden it’s also worth growing on ridges or in raised beds to avoid wet, waterlogged conditions.

White rot can also be a problem but if you stick to a good rotation system you should be able to avoid it. Do please heed this advice as if you do get it you won’t be growing onions in your garden for 7 years. You’ve been warned!

Varieties for Spring Planting:
Santero F1
Resistant to downy mildew which can ruin gardeners onion crops. Santero produces an excellent quantity and quality of onion without any mildew problems, great news for onion growers. Stores extremely well.

An RHS Award of Garden Merit variety producing well sized semi-round bulbs with good keeping qualities. A standard, round globe shape with a sweet and mellow flavour, yellow flesh and light brown skin. Sturon is bolt resistant and stores very well.

CentrurionCenturion is an early maturing variety that keeps well. Uniformly globe shaped bulbs with even skin colour – excellent eating onions which are good enough to show.

Rumba Onion sets are a top performing crop variety that’s ideally suited to growing in the our climate. Producing high yields of large round onions with a sweet flavour. A good all rounder.

Stuttgart onion sets produce firm semi flat shaped onions with a vibrant golden skin colour. They have a deliciously crisp and mild flavour, are slow to bolt and store very well.

Varieties for Autumn Planting:
Radar onion sets for autumn plantering and overwintering. They are extremely frost hardy and produce nice round bulbs.

Shakespeare is a brown skinned variety with excellent storage potential. Has good resistance to bolting.

Senshyu Yellow
Senshyu Yellow onions are a very popular overwintering Japanese variety that have a high yield. These yellow globe onions are a very hardy variety with golden skin and white flesh.

Red Winter
Red Winter onions are a heavy yielding variety of autumn onions that store very well. They are a mid to late maturing variety that are great for cooking with or using as an addition to any salad.

Onion Seed: Golden Bear F1
This is the one to grow if you have ever had White Rot on your onions as this variety is resistant to it. It also has good resistance to grey mould and some tolerance to downy mildew. Matures early and has a very high yield of perfect onions.

Spring Onion: Ishikura Bunching
An outstanding variety, perfect for bunching. Leaves are upright and dark green with straight long white stem. If you’ve been disappointed by spindly spring onions in the past, try this you’ll never turn back! Perfect.

Time to plant onions!

How sweet it is – Noonday Sweet Onions, that is. You don’t have to live in Noonday, Texas to grow your own crop of tasty onions, though. Several factors are involved in producing a successful onion crop. The first factor for success is planting the right varieties. Onion varieties are classified as short-day, long-day and intermediate. Plant the wrong type, and you won’t get a bulb! Short-day onion varieties are the best for our area, although intermediate types will also produce bulbs here in northeast Texas.

One of the more popular onions adapted for our area is the 1015Y or Texas SuperSweet onion, developed by Texas A&M for the Texas onion industry for disease resistance and good size. A bonus was the incredibly mild flavor of this onion. Home gardeners have reaped the benefits of A&M’s research since this is a great variety for backyard gardens. Other varieties for our area include Yellow and White Granex, White Bermuda (also called Crystal Wax), Grano 502 (literally mother of all the sweet onions) and Red Burgundy. Sweet Red and Cimarron are 2 popular intermediate types.

Timing of onion planting is also important. Short day types are planted late January through mid-February, while intermediate types can be planted from early February through early March.

Pick onion transplants that about pencil size, no bigger, to reduce risk of bolting.

When buying onions, don’t grab the bundles with the fattest plants. The best size transplant is about the size of a pencil or slightly smaller. Any bigger and they may bolt, or flower, resulting in a hollow center and shorter shelf life. Don’t be concerned if they look a little dried. The onion is a member of the lily family and will live for approximately three weeks off the bulb. The first thing that the onion will do after planting is grow new roots.

Onions prefer a fertile, well-drained sandy loam. Make raised beds if your soil is poorly drained to reduce the impact of drenching rains and help warm up the soil more quickly in the spring. Raised beds allow the soil to dry quickly, which is important when the bulbs are nearing maturity. A raised bed of soil 4 inches high and 20 inches wide will allow you to plant two rows of onions down the bed.

Some east Texas soils might be too acidic for good onion growth. If a soil test indicates a soil pH below 6.0, add lime to bring the pH between 6.0 and 6.5.
Early onion growth and yield is promoted by banding a fertilizer rich in phosphorous 2 to 3 inches below transplants at planting time, and plant the transplants so their roots are not touching the fertilizer band.

Set the plants approximately 1 inch deep, 4 inches apart, and 4 inches from the edges of the raised bed. If you want to harvest green onions during the growing season, set transplants 2 inches apart and gather every other one before they begin to bulb.

If you are after large onions, keep this fact in mind: for every leaf there will be a ring in the onion. The larger the leaf, the larger the ring will be. Onions will first form a leafy top, and then, once the proper day length arrives, bulbs will begin forming. Steady soil moisture and adequate fertility during the growth phase are needed to keep those plants growing more leaves.

Mulch will help conserve water, and a drip or soaker hose down the row is a good way to keep the soil moist. The most critical time for water is from bulb initiation until they begin to mature.

Soils rich in nitrogen will produce bigger plants and bulbs. Organic fertilizers high in nitrogen, like cotton seed meal, should be worked into the soil when the beds are made. Side dress with supplemental nitrogen about 3 or 4 weeks after transplanting, and continue monthly until the neck of the bulb starts to feel soft. This should happen about 4 weeks before harvest.

Do not pull soil from around the bulbs to make them larger – it does not trigger bulbing or increase bulb size, but can result in sunburning which turns the top of the bulbs green.

When onions are mature, they develop a soft neck and the tops will naturally begin to fall over. At this time, withhold water to let the bulbs properly cure and dry. “Walking down the tops” does not hasten maturity, as some farmer fables claim, and actually can reduce yields.

Pull onions when they are ready for harvest and cure them in a dry place for several days. After curing, clip the top, leaving about 1 inch of stem attached to the bulb, and let them cure a few more days to help prevent rot organisms from entering.

From leeks and shallots to red salad onions, the members of the onion family are an incredibly versatile lot and they’re wonderful crops to grow at home too. For most areas, now is the time to sow seed or plant seedlings and it’s particularly urgent in warmer areas where true onions need a long cool growing season to fully develop. If you’re in a cool area you can delay planting some varieties until winter.

Onions need full sun and excellent drainage. They like a soil that’s high in organic matter, but not overly rich. A good spot to choose is one where a leafy vegetable has just been harvested – in other words, a well-prepared area where most of the nitrogen has been used up by the previous crop. Too much nitrogen will result in excessive leaf growth at the expense of sweet white swollen bulbs. pH is important. Onions need something around 6.5. Add lime or dolomite if necessary to sweeten the soil and you’ll be guaranteed the best results.

All onion seeds look the same – weird and angular – like oversized grains of black sand. They are easy to sow, but must be fresh. If you have an old packet sitting around that’s passed its use by date, toss it out and buy a new pack. I find that sowing into punnets is the best way to go as it gives you greater control over spacing when they go in the ground. If you can’t be bothered with seed, a $3 punnet from your local nursery is great value and they usually contain up to 50 seedlings or more.

Seedlings are ready to plant out when they get to 10-15cm long. Pull them out of the punnet and shake all of the potting mix off the roots then separate them into individual plants. No need to be overly gentle, they can handle some fairly rough treatment.

Planting them out is easy. Just make a 5cm deep groove or trench in the soil, lay the seedlings down at their required spacing with the roots at the bottom of the trench and then backfill. Don’t worry that the plants are lying flat on the soil surface; within a week or so, they will stand upright again all by themselves.

Once that’s done, water them in well with a liquid seaweed preparation and you’re on your way. Leeks, red, white, brown onions and shallots all need a regular drink to perform well so remember to look after them on those dry days.

Some other things to remember:

  • Avoid high nitrogen fertilisers, particularly in the final stages of maturity
  • True onions take around 6 months to develop and are ready to harvest when the tops yellow.
  • Spring onions are basically white onions harvested young. Harvest them any time.
  • Shallots are the easiest of the bunch to grow and can be grown any time of year in most areas.

First published: March 2010

Onions To Grow Over Winter: How Do You Grow Winter Onions

Winter onions are a form of multiplying onion grown for the flavorful green tops and for the bulbs, which are typically harvested when they are 3 inches in diameter or less. Winter onions are basically the same as “regular” onions, except they grow in bunches and the flavor is slightly milder. As the name suggests, winter onions are great onions to grow over winter. They are also known as potato onions or ground onions.

How to Grow Winter Onions

Winter onions can actually be planted in spring or fall. However, onions planted in fall generally produce larger yields. Many gardeners like to plant onions in fall, then save a few small onions in a dry location for planting in spring.

Winter onions can be planted any time the ground can be worked – usually between October and December in most climates – or two to three weeks before the first hard freeze. Growing winter onions require full sun, as the onions won’t grow in shade.

Plant the onions 2 to 4 inches deep, allowing 4 to 6 inches between each bulb. Water well. The onions are underground and tolerate cold weather. However, a layer of mulch is helpful for overwintering onions in cold, northern climates.

You can also plant winter onions in a container. Keep the container near the kitchen door and harvest onions for use throughout the winter. A container with a width of at least 18 inches is best.

Harvesting Winter Onions

Harvest the first winter onions two to three months after planting. Although you can harvest earlier, the onions will be very small and they won’t have time to multiply. (When allowed to mature, each bulb usually produces seven or eight bulbs.)

Continue to pull or dig onions until spring. To save a few for fall planting, allow the tops to dry before pulling, then lay the onions in the sun for a few days so the outer covering dries. Store the onions in a cool, dry location until fall planting time.

Best Winter Onions

Many types are available and the best way to determine the best winter onions for your area is to experiment with different varieties. Example of popular winter onions include:

  • White multiplier onions, which develop thumb-size bulbs
  • Yellow potato onions, heirloom onions that have been around for well over 200 years.

Others include:

  • Kentucky Hill
  • Red
  • Yellow
  • Greeley’s

Winter Onions

By Jodi Torpey

Are you the kind of grower who’s ready for a new gardening challenge? If so, you might enjoy growing winter onions.

Winter onions are planted in fall and spend the winter in the garden so they’re ready to harvest in early spring. If you’re up for the challenge, you can get started with help from onion experts, such as Dr. Becky Sideman.

Sideman, an extension professor in sustainable horticulture and a researcher with the New Hampshire Agricultural Experiment Station in Durham, N.H., has researched ways to overwinter onions in a cold climate and has a few words of advice for other growers: Don’t be afraid to experiment in your own garden.

The three keys to overwintering onions include selecting the right varieties or cultivars, planting them at the right time, and giving plants winter protection, she says.

“One of the biggest problems with overwinter plantings is that onions are biennial, and once the plants experience winter, they tend to flower or bolt (go to seed),” she says. “Varieties differ greatly in their susceptibility to bolting after experiencing cold temperatures.”

To overcome bolting, growers should choose onion varieties that are known to overwinter in their region. The research in New Hampshire included 18 different varieties of bulb onions (Allium cepa) . The varieties found to resist bolting included Bridger, Gatekeeper, High Keeper, Keepsake, and Tough Ball yellow onions; and Desert Sunrise and Electric red onions.

The research showed “choosing varieties that have been selected for overwintering, ideally in your region, will decrease the chances of bolting and increase the chances of getting nice bulbs,” Sideman says.

Sometimes winter onions are sold as “autumn planting onion sets” or sets produced of bulb varieties suitable for fall planting. Check with your county’s extension office to see about specific recommendations for your region.

Multiplier or potato onions (Allium cepa aggregatum) are another type of overwintering onion. These onions grow small bulbs similar in size to shallots. Multiplier onions grow in clusters, like potatoes, and one set can grow as many as 8-12 small, but tasty, onions. Multiplier onions may be another way to avoid onion bolting if you’re satisfied with smaller bulbs.

The combination of the right varieties and matching them to their prime planting dates makes for successful overwintering. Planting dates will vary by hardiness zones, but most fall-planted onions are in the ground between September and December.

Multiple planting dates, spread over several weeks, are a good method to find what works best in your region for reducing the risk of bolting and increasing the chance of growing market-sized onions.

Fall onion planting is similar to spring planting. Whether planting in the garden or a raised bed, onions need a sunny location. Plant either onion sets or onion transplants about 1 inch deep and about 4-6 inches apart in rich, well-draining soil. Water after planting.

Fall-planted onions can be protected with a layer of straw mulch, row cover fabric, or no protection at all, Sideman says. In the New Hampshire growing experiment, onions were planted four different ways, but onions showed consistently good winter survival in low tunnels covered with row cover cloth, she says.

When onions start growing in spring, the plants need irrigation to develop good-sized bulbs. Remove the low tunnels when daytime temperatures reach 60 degrees and nighttime temperatures remain above 20 degrees, Sideman says. Onions are ready to harvest when the green tops have fallen, but before the foliage dries completely.

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