Onion nursery management is the work of turning a few kilogrammes of seed into a known number of pencil thick seedlings on a date you chose. A tenth of a hectare of seedbed supplies a hectare of crop, so a small patch of ground carries the whole season. Expect to sow somewhere between a third and twice as many seeds as you want plants, and to move them at the three leaf stage.
Why the Onion Nursery Carries the Whole Crop's Risk
Onion in Uganda is raised in a bed and moved, only rarely sown where it will grow, and that bed is where three things get settled which the field cannot fix afterwards. How many plants you end up with, which sets your population and your yield ceiling. When they go out, which sets your harvest month and the price you meet. And how good each seedling is, because a weak transplant sits in the field for weeks recovering while a strong one starts growing.
Ugandan growers buy their onion seed from agro input dealers, which a farm survey across all three major growing regions confirmed. There is no national variety list to check the pack against, and the day length class on that pack is settled before the nursery starts, so the seed buying guide is where that decision belongs. Everything on this page assumes you have already made it.
How Much Nursery Bed an Acre of Onions Needs
This is where most people start guessing, and the best available source turns out to contradict itself, so it is worth working through rather than copying.
A regional seed company's onion production guide gives three figures. It says 3 to 5 kg of seed produces the 600,000 seedlings needed for a hectare of crop. It says to sow 7 to 10 grams of seed per square metre of seedbed. And it offers a rule of thumb that one hectare of seedbeds supplies enough seedlings for ten hectares of crop.
For a first acre, a bed area somewhere between 250 and 400 square metres is a defensible starting point on those figures, and you should record what it actually produced so the next season's number is your own rather than anybody else's.
Onion Seed Rate and What the Circulating Figures Get Wrong
Pages ranking for Ugandan onion widely give a seed rate of 4 to 6 kg an acre. Check it against the sourced figures and it does not hold up.
| Figure | Value | Where it comes from |
|---|---|---|
| Seed for a transplanted hectare | 3 to 5 kg | Seed company production guide |
| The same, per acre | about 1.2 to 2 kg | Converted from the above |
| Seed for a direct seeded hectare | 6 to 8 kg | Same guide |
| The same, per acre | about 2.4 to 3.2 kg | Converted from the above |
| Sowing density in the bed | 7 to 10 g per square metre | Same guide |
| Seed count | about 270,000 seeds per kg | Same guide |
So the circulating figure is two to five times what a transplanted acre needs and roughly double what a direct seeded one needs. The likely explanation is simple: a per hectare number relabelled as per acre somewhere along the chain of pages copying each other. Onion seed is expensive enough that the difference is real money, and the seed rate calculator will do the conversion for whatever your own layout turns out to be.
One more number falls out of the guide's own three figures and it is the most useful thing on this page. At 270,000 seeds a kilogramme, 3 to 5 kg is between 810,000 and 1,350,000 seeds sown to yield 600,000 transplantable seedlings. That is a strike rate of roughly 44 to 74 percent from seed to usable seedling, and the arithmetic is mine from the guide's figures. Sow the exact number of seeds you want plants and you will be a quarter to a half short. Run a germination count on your own batch before sowing so you know which end of that band you are working with, because the percentage printed on a label is a laboratory figure and your bed is not a laboratory.
Siting and Preparing the Onion Seedbed
Four siting decisions, and they are all made before you touch a hoe. Put the bed where you can get water to it two or three times a day, because that is the watering regime a germinating onion bed needs. Put it in full sun, since a shaded bed makes drawn weak seedlings. Put it where you can see it daily, because damping off spreads over days rather than weeks. And keep it off ground that has just carried onion, garlic or another crop from the same family, which is the same rotation logic that applies to the field.
Preparation is about tilth rather than depth. Onion seed is small and the bed needs a fine, level surface with no large clods, because a seed that lands in a gap between clods either dries out or gets buried too deep. Beds run 1.2 to 1.6 m across the top, carrying six or eight rows about 20 cm apart. Make the bed short enough that you can reach the middle from both sides without stepping on it, and leave a path round it.
Raised beds are the sensible default in Uganda for the same reason they are elsewhere: they drain, and a saturated onion nursery loses seedlings to damping off faster than a dry one loses them to drought.
Nursery Medium for Vegetable Seedlings in Uganda
If you are sowing into open ground, the medium is your soil plus whatever you work into it, and the aim is fine textured and free draining rather than rich. A Ugandan onion trial raising seedlings in trays used sandy loam soil mixed with chicken litter at a ratio of four parts soil to one part litter, homogenised before filling. That is what one trial used rather than a rate to copy, because poultry litter varies a great deal in strength and a hot litter at that ratio will burn onion seedlings. How poultry manure behaves as a fertilizer covers why, and composting it properly first is the safer route.
There is also Ugandan work on substituting nursery medium that is worth knowing about, with a caveat. A Makerere trial replaced peat with biochar at rising proportions for vegetable seedlings. Replacing a fifth made no measurable difference against an all peat control, at 49.2 mm of seedling height against 48.71. Replacing two fifths dropped height to 43.07 mm and three fifths to 36.47, with collar diameter and leaf area moving the same way. The crops were tomato, cabbage and capsicum. Onion was not one of them, so do not read this as an onion result.
The transferable principle is the shape of the curve: a modest substitution into a known medium cost nothing measurable in all three crops tested, and a large one cost seedling size in all three. If you are cutting your medium with something cheaper, cut it lightly and keep a control block of the old medium so you can see what it did.
Sowing Onion Seed at the Right Depth
Depth is a short section with a long argument behind it, because two sources say different things and one of them contradicts itself.
Practically: open shallow drills with a stick, sow along them, and cover with fine soil to about the depth of the seed's own width several times over rather than by burying. Then mulch the bed surface lightly with dry grass, which holds moisture at the surface between waterings and is the cheapest thing you can do for germination.
Watering an Onion Seedbed Without Losing Seedlings to Disease
The watering rule for a freshly sown onion bed is the one the production guide states plainly: the soil surface must not be allowed to dry out, which means short irrigation cycles two or three times a day depending on the weather. Note the shape of that instruction. Short and frequent, not long and occasional.
That is because the two failure modes pull in opposite directions. A surface that dries out kills germinating seed outright at the point where it has broken the coat and has no root yet. A bed kept saturated starves the seed of oxygen and then hands the survivors to damping off. So you are aiming at damp rather than at wet, and you are aiming at it several times a day rather than once.
Two habits make the difference. Water in the morning and early afternoon rather than at dusk, so the surface is not sitting wet overnight. And lift the mulch to check the soil underneath rather than judging by the surface, because mulched beds look drier than they are.
Feeding Onion Seedlings, and Why Less Is Better
The production guide is direct about nursery nutrition: it says it is important that not too much nitrogen is given to the growing seedlings, and puts the figure at approximately 30 to 50 kg of nitrogen a hectare of seedbed. On a bed of a few hundred square metres that is a small quantity, which is the point.
An overfed onion seedling is soft, tall and dark, and it transplants badly. What you want is a seedling that is thick for its height, and thickness comes from light and from moderate feeding rather than from pushing growth. If the medium already carries composted manure, the seedlings may need nothing at all.
The same restraint applies to water in the last week before lifting. Easing off firms the seedling up, and a firmer seedling survives the move better. No Ugandan source publishes a hardening period in days for onion, so work to the plant rather than to a calendar: reduce the water and increase exposure until the seedlings stand stiff rather than flopping when you brush a hand across the bed.
Damping Off and Other Onion Seedling Losses
Damping off is the named nursery disease for this crop and it is a conditions problem before it is a pathogen problem. Seedlings emerge, then fall over at soil level with a pinched water soaked stem base, in patches that grow outward. The drivers are all things you control: a medium held too wet, seed sown too thickly, no air moving between seedlings, and a surface that never dries out at all.
The controls are physical and they are free. Drain the bed. Sow at the density the guide gives rather than heavier, since thick sowing is the commonest cause. Water in the morning. Take patches out as soon as you see them, medium included. Reuse trays only after washing them out, and do not top up a failing bed with new medium over the old.
Nematodes and soil pests also sit at the nursery stage on the production guide's own calendar. Nematode trouble shows on a lifted seedling rather than on a standing one: stunted plants with knotted or stubby roots that do not match the top growth. Lift a few doubtful seedlings and look at the roots before you conclude anything about the leaves. This page names no seed dressing and no soil treatment, because the rate for any such product is on the label of one currently registered in Uganda and a district extension officer is the person to confirm it.
Trays and Plugs Against an Open Ground Seedbed
Trays look like the modern option and for onion they come with a specific limitation. The production guide records that tray raised onion seedlings reach only 3.0 to 3.5 mm in diameter, which is thinner than a bed raised seedling, and it warns against a shortcut growers reach for: planting a whole plug without separating the seedlings inside it. Clusters planted together do not develop properly and produce malformed bulbs with flattened sides. So if you use trays, you separate every plug by hand at planting, and that is slow work.
Direct Seeding Instead of Raising a Nursery
Direct seeding deserves a fair hearing because it removes the two hardest jobs in the sequence, and it fails for a reason that is easy to underestimate. The seed requirement roughly doubles, to 6 to 8 kg a hectare. That is affordable. What is not always affordable is the weed control: the entire field has to be kept clean while the onion seedlings are still small and weak, instead of one small bed, and onion competes badly with weeds at every stage. Irrigation is harder too, because you need small amounts applied often and evenly across the whole field until germination finishes rather than across a few hundred square metres.
Where it wins is timing. A direct seeded crop matures about six weeks earlier than a transplanted one, which on a crop whose price swings hard by month can be worth more than the seed and the weeding put together. Read it against the harvest month you are aiming at, which is where the onion growing guide works the whole season backwards from a dry finish.
For reference, direct seeding is the minority method where anybody counts it: an Indian research body puts the direct seeded share at 10 to 15 percent of area against 85 to 90 percent transplanted. No Ugandan split is published, so read that as an indication from elsewhere rather than as a local figure.
When Onion Seedlings Are Ready to Transplant
Not on a date. Two Ugandan trials, run independently for entirely different purposes, both moved their onion seedlings at the three leaf stage, and one of them recorded the seedlings as pencil sized and slightly over four inches high at 45 days from sowing. The seed company guide gives pencil thick at about six to eight weeks. Those agree: a thickness, with an age as the rough expectation rather than the trigger.
Bear in mind what a three leaf onion is. A well grown onion plant in the field carries something like seven to nine leaves in Ugandan measurements, against a reported thirteen for a plant grown to its potential. A three leaf seedling is an early plant being moved deliberately young, which is why the handling in the next section matters as much as the timing.
Lifting and Moving Seedlings Without Setting Them Back
Water the bed thoroughly a few hours before lifting so the soil releases the roots instead of tearing them. Lift rather than pull, working a tool under the row, and keep the seedlings shaded and their roots damp between the bed and the field. Sort as you go and discard anything thin, bent, or showing a collapsed stem base, because a weak seedling planted out is a gap in the row three weeks later.
Planting is done into shallow furrows opened on top of the field bed, with the seedlings laid at a slant against the side of the furrow and the roots covered to 1 to 2.5 cm. They will lie flat for a few days and then stand up on their own once the settling waterings have gone in, which alarms first time growers and should not. Water daily until they are upright.
Transplant in the cool of the late afternoon, or under cloud, so the seedlings are not fighting heat on the day they have no root contact. Then get the field spacing and the population right, which the growing guide covers and the plant population tool will check for you against the bed you have built.
Buying Seedlings Instead of Raising Them
Buying in seedlings moves risk around rather than removing it. It takes away the two or three months of daily watering, the damping off exposure and the nursery land, and it hands you three new problems: you do not know what variety you actually received, you do not know the day length class, and you inherit whatever disease was in somebody else's bed.
If you go that route, buy from a nursery you can walk into and inspect, look at the seedlings against the four checks above before money changes hands, and get the variety name written on the receipt. The economics are a different question and running a seedling nursery as a business is a separate enterprise from raising your own.
Buying Onion Seed and Costing It Per Surviving Seedling
The number that matters when you are buying is not the price of the sachet. It is the cost per seedling that actually reaches the field, which on the strike rate above means paying for between a third and twice as many seeds as you will plant. Check current onion prices to sanity check the harvest month you are sowing towards, work through the input supplier listings for who stocks onion seed near you, and ask two questions at the counter: the day length class, and the germination percentage on the label. The cost of onion farming puts the seed and nursery lines against everything else an acre needs. All of it sits inside the wider vegetable farming section.
Onion Seedling Questions Growers Ask
How long does an onion nursery take?
Six to eight weeks to pencil thickness on the production guide's figure, and one Ugandan trial transplanted at 45 days. Treat it as six weeks minimum and check the seedlings weekly from there, because temperature and watering move the date by a fortnight either way.
How big should the nursery bed be for one acre?
Between about 121 and 289 square metres on the seed rate and sowing density, or about 405 square metres if you follow the one to ten rule of thumb from the same source. Those two do not agree, which is why the page shows the arithmetic. Build the larger one on a first crop and record what it actually produced.
How many kilogrammes of onion seed do I need per acre?
About 1.2 to 2 kg for a transplanted acre, and about 2.4 to 3.2 kg if you direct seed. The 4 to 6 kg an acre that circulates for Uganda is two to five times the transplanted requirement and looks like a per hectare figure that got relabelled.
Why did so few of my onion seeds produce usable seedlings?
Some loss is normal and it is larger than most growers expect. Working the production guide's own figures, 3 to 5 kg of seed at 270,000 seeds a kilogramme is 810,000 to 1,350,000 seeds sown for 600,000 seedlings, a strike rate of roughly 44 to 74 percent. Beyond that band, look at sowing depth, at whether the surface dried out during germination, and at damping off.
Can I sow onion seed straight into the field?
Yes, and it is a real option rather than a compromise. It doubles the seed, removes the transplanting labour and brings maturity forward by about six weeks. The cost is that the entire field has to be kept weed free and evenly watered while the seedlings are tiny, which is harder than doing the same for one bed.
How deep should onion seed go?
Around 10 to 12 mm, and the Ugandan methods figure of roughly a quarter to a half inch brackets it. One Ugandan paper's abstract says 4 to 5 cm, which contradicts its own methods section and is too deep for the seed to emerge from reliably. Go shallow and mulch the surface.
Is it cheaper to raise onion seedlings or to buy them?
No figure appears here, because seedling prices in Uganda cannot be sourced to anything better than a listing, and the cost page carries the input stack. The question worth asking instead is which risk you would rather hold: raising your own costs daily labour for two months and gives you control of the variety and the health of the bed, while buying in saves the labour and hands you somebody else's seed and somebody else's disease.
Do I need to treat the nursery soil before sowing?
Start clean rather than start treated. Fresh or well composted medium, washed trays, a bed that has not just carried onion or a relative, and drainage. A Ugandan research trial sterilised its trays and seed with laboratory reagents, which is not farm practice and is not repeated here. Any product rate belongs on the label of one registered for the purpose in Uganda, confirmed with an extension officer.
What does a good onion seedling look like at transplanting?
Three leaves, pencil thick at the base, around 10 cm tall, stiff rather than floppy when you brush a hand across the bed, and with a clean white stem base and no pinching at soil level. Thickness matters more than height, and a tall thin seedling has usually been shaded or overfed.