The agricultural landscape in Kenya is shifting rapidly from the vast open fields of the Rift Valley to the concrete balconies of Nairobi, Kiambu, and Eldoret. Urban farming is no longer just a hobby for the retired; it is a serious economic survival strategy for families looking to beat the rising cost of living. Growing bulb onions in crates is one of the most efficient, high-value ways to utilize small spaces like balconies, rooftops, and backyards. Unlike leafy greens that spoil quickly, onions have a long shelf life and high market demand, making them a “gold bullion” crop for the urban farmer.

This master guide will take you through every single detail of growing onions in milk or bread crates. We are not just talking about throwing seeds in soil; we are talking about precision agriculture adapted for the Kenyan urban context. You will learn how to mix your soil to replicate the fertile loams of Oloitokitok, how to source the best F1 hybrid seeds from certified Kenyan suppliers, and how to manage pests like Thrips without destroying your ecosystem. Whether you are in a high-rise in Kilimani or a plot in Syokimau, this guide is your roadmap to harvesting premium red onions right outside your door.

CURRENT MARKET ANALYSIS AND PROFITABILITY IN KENYA

Before you buy your first crate, you must understand the financial terrain of onion farming in 2026. As of January 2026, the retail price for dry onions in major markets like Wakulima (Marikiti) and Kongowea ranges between KES 60 and KES 100 per kilogram depending on the quality and origin. Prices recently spiked due to weather conditions affecting local supply, pushing families to seek alternatives to buying from the “mama mboga.” While farm-gate prices can fluctuate down to KES 30 during peak harvests when Tanzanian onions flood the market, urban crate farmers have a distinct advantage. You are not subject to transport costs, broker fees, or post-harvest losses associated with long-distance shipping. Your “farm-gate” is your kitchen door.

The profitability of crate farming lies in density and turnover. A standard plastic milk crate (approx. 60cm by 40cm) can comfortably hold 15 to 20 large bulbs if spaced correctly. If you stack your vertical space or utilize a small 5×5 meter rooftop area, you can manage over 100 crates. With a yield of roughly 2 to 3 kilograms per crate (depending on the variety and care), a 100-crate system could yield 200-300 kgs of onions per cycle. At a conservative market saving of KES 80/kg, that is KES 24,000 worth of produce that you did not have to buy, produced with minimal inputs.

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Furthermore, the price of inputs has stabilized but remains high, making homegrown food even more valuable. DAP fertilizer is currently retailing around KES 4,500 to KES 6,400 per 50kg bag depending on the vendor, and certified hybrid seeds like Jambar F1 are premium priced. However, in a crate system, your input usage is fractionally small. You are not wasting fertilizer on weeds or leaching it into deep soil. Every granule of DAP or CAN you apply goes directly to the bulb, making crate farming one of the most cost-efficient methods per square foot of production.

CHOOSING THE RIGHT ONION VARIETIES FOR CRATES

Selecting the right seed is the first critical decision you will make. In Kenya, we generally have two categories of onions: Open Pollinated Varieties (OPVs) and F1 Hybrids. For crate farming, where space is expensive and you need guaranteed returns, F1 Hybrids are often the better choice despite the higher seed cost. They offer disease resistance, faster maturity, and uniform bulb sizes, which is crucial when you want every inch of your crate to be productive.

Jambar F1 is currently one of the most popular varieties in Kenya for good reason. It is a high-yielding red onion that produces deep red, globe-shaped bulbs. It is favored for its strong pungency, which is a key preference for Kenyan consumers who use it for frying sukuma wiki and meat stews. Jambar F1 matures in about 90 days after transplanting, which is relatively fast. Its resistance to Pink Root and Fusarium Basal Rot makes it a safer bet for beginners who might struggle with soil-borne diseases in a contained environment.

Red Creole is the classic choice if you prefer open-pollinated seeds. It is widely available at almost every agrovet in Kenya, from Kenya Seed Company stockists to small village shops. Red Creole is famous for its excellent shelf life; you can store these onions for up to six months in a dry, well-ventilated area without them sprouting. However, it takes slightly longer to mature (up to 150 days) and the bulbs tend to be flatter compared to the high-globe shape of hybrids. If you are farming for your own long-term storage, Red Creole is a fantastic, low-cost option.

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Neptune F1 and Red Pinoy are other excellent contenders. Red Pinoy is an early maturing variety that is perfect if you are in a rush to get a harvest. It can be ready in as few as 90 days. Neptune F1 is known for its uniformity. When growing in crates, you want onions that grow at the same speed so they don’t overshadow each other. Neptune delivers this consistency, ensuring that when you harvest one crate, almost all the onions are of marketable size.

SOURCING AND PREPARING YOUR CRATES

The foundation of this system is the crate itself. You do not need to buy brand new expensive planters. The black plastic crates used for milk or bread delivery are ideal because they are durable, deep enough for onion roots (which are shallow), and have built-in handles for moving them around. You can find these second-hand in markets like Gikomba in Nairobi, Kibuye in Kisumu, or hardware sections in major towns. Expect to pay between KES 150 and KES 300 per crate depending on its condition and your bargaining skills.

Once you have your crates, you cannot simply fill them with soil. The large holes on the sides and bottom will let all your soil wash away during watering. You need to line the crates. The best material for this is the porous sacks (gunny bags or “magunia”) often used to package potatoes or charcoal. Do not use solid plastic sheeting or garbage bags, as these will trap water and cause root rot. Onions hate “wet feet.” Cut the sacks to fit the inside of the crate, ensuring the bottom and sides are covered.

Secure the sack lining to the crate using binding wire or strong twine. Stitch it through the crate holes so it stays firm when you pour in the heavy soil. Ensure that the lining is not too thick at the bottom; you want excess water to drain out freely. If you are placing the crates on a concrete balcony, place them on bricks or wooden blocks to elevate them slightly. This prevents the bottom from sitting in a puddle of water and allows air to circulate underneath, which air-prunes the roots and prevents fungal diseases.

FORMULATING THE PERFECT SOIL MIX

Onions are heavy feeders but they need loose, well-draining soil to expand their bulbs. If the soil is too hard or compact (like pure clay), the bulbs will be small and deformed. If the soil is too sandy, it won’t hold enough water or nutrients. For crate farming in Kenya, we use the “3:2:1 Rule” to create the perfect potting mix. This ratio represents 3 parts Topsoil, 2 parts Manure, and 1 part River Sand.

The topsoil should be sourced from a reliable area, preferably Red Kikuyu Loam or similar fertile soils found in agricultural zones. Avoid soil from construction sites as it often contains cement and chemicals. The manure must be “boma manure” (cow or sheep) that is well-decomposed. Do not use fresh manure; it is high in ammonia and will burn the tender onion roots (a condition farmers call “burning”). The manure should look like dark earth and have no strong smell. This provides the nitrogen and organic matter needed for leafy growth.

The third component, river sand, is non-negotiable. You can buy a wheelbarrow of sand from local construction suppliers. Sand ensures that the soil mixture remains loose and drains water instantly. Onions grown in crates without sand often suffer from waterlogging. Mix these three components thoroughly on a tarp or a clean concrete floor before filling your crates. At this stage, you should also mix in a handful of DAP fertilizer (about 50g per crate) to provide the phosphorus needed for strong root development immediately after transplanting.

ESTABLISHING AN ONION NURSERY

While you can direct seed onions into the crates, it is highly inefficient for space. Onion seeds are tiny and take about 6-8 weeks to reach transplanting size. If you direct seed, your crates will be occupied by tiny grass-like seedlings for two months, wasting valuable production time. The professional approach is to start seeds in a separate “nursery basin” or a dedicated nursery crate, and then transplant only the strongest seedlings to your main crates.

To make a nursery, use a plastic basin or a single crate with the same soil mix described above. Smooth the soil surface until it is perfectly flat. Draw shallow lines (drills) across the soil about 2cm deep and 5cm apart. Sprinkle the seeds thinly along these lines. Do not bury them deep; cover them lightly with a thin layer of soil or fine sand. Water gently using a watering can with a fine rose (head) so you don’t wash the seeds away.

Cover the nursery container with a damp gunny bag or dry grass mulch to retain moisture and keep it dark, which speeds up germination. Check every day. As soon as you see the tiny “loops” of onion seedlings breaking the surface (usually 5-7 days), remove the cover immediately to let them get sunlight. If you leave the cover on too long, the seedlings will become tall, white, and weak (etiolated). Keep the nursery moist but not soaking wet. Weekly foliar feeds with a vegetative booster can help them grow sturdy stems.

TRANSPLANTING: THE PENCIL THICKNESS RULE

Your seedlings are ready to transplant when they are about the thickness of a pencil (or slightly thinner) and have at least 3 to 4 true leaves. This usually happens 6-8 weeks after sowing. Do not rush this. If you transplant too early, the delicate seedlings may die from shock. Two days before transplanting, reduce watering to “harden off” the seedlings. This toughens them up for the move.

On the day of transplanting, water the nursery heavily so the soil is soft. Gently pull out the seedlings, trying to keep as much root as possible. Expert farmers use a technique called “trimming.” Use a clean pair of scissors to trim the roots to about 2cm long and trim the top leaves by about one-third. Trimming the roots stimulates new root growth, and trimming the tops reduces water loss through transpiration while the roots are re-establishing themselves.

In your main production crates, water the soil well before planting. Use a stick or your finger to poke holes. The spacing is critical: 10cm to 15cm between plants is ideal for crates. In a standard crate, you can arrange them in a grid-4 rows by 5 plants, totaling 20 onions. Do not plant them too deep. The tiny bulb at the base of the stem should be just below the surface, but the point where the leaves fan out must be above the soil. If you bury the neck, the onion will not bulb properly. Firm the soil around the base of each seedling.

WATERING AND MANAGEMENT FOR CRATES

Container gardening requires different watering discipline than field farming. In a field, roots can go deep to find moisture. In a crate, they are prisoners. If the crate dries out, the plants stop growing immediately. In the hot months of January to March, you may need to water every day or every two days. The rule of thumb is the “finger test.” Poke your finger an inch into the soil. If it feels dry, water. If it is damp, wait.

However, beware of overwatering. Nairobi’s cool season (June-July) brings low evaporation rates. Watering daily during this time will lead to fungal diseases like Downy Mildew. Always water in the morning (between 6 AM and 9 AM). This allows any water splashed on the leaves to dry off during the day. Wet leaves at night are a recipe for disease.

Weeding in crates is easy but necessary. Since you used clean soil and manure, weeds should be minimal. Pull them out by hand as soon as you see them. Weeds in a confined crate compete aggressively for the limited nutrients. You should also aerate the soil occasionally by lightly scratching the surface with a small fork, being careful not to damage the shallow onion bulbs.

FERTILIZER APPLICATION REGIME

Onions are hungry crops. The manure you put in the soil mix is a great start, but for big, market-quality bulbs, you need to supplement. We have already added DAP during planting for root establishment. The next critical stage is the vegetative growth phase, where the plant builds the leaves that will eventually fuel the bulb size.

About 3 to 4 weeks after transplanting, apply a nitrogen-rich fertilizer. CAN (Calcium Ammonium Nitrate) is the standard in Kenya. For a single crate, you only need about one tablespoon (10-15 grams). Sprinkle it carefully between the rows, ensuring the granules do not touch the plant stems or leaves, as they will burn the plant. Water immediately after applying to dissolve the fertilizer into the root zone.

The second top dressing should happen about 6-8 weeks after transplanting, just as the bulbing process begins. At this stage, switch to a balanced fertilizer or one higher in potassium, like NPK 17:17:17. Potassium is the element that makes fruit and bulbs swell. Avoid excessive nitrogen at this stage (don’t use Urea), as it will encourage thick necks and leafy growth but delay bulb formation and reduce storage quality.

PEST AND DISEASE CONTROL

The two biggest enemies of onion farmers in Kenya are Thrips and Downy Mildew. Thrips are tiny, microscopic insects that hide deep in the center of the onion leaves. They suck the sap, causing the leaves to turn silvery or white and dry up. If you see your onion leaves looking like they have silver streaks, you have Thrips. Because crates are often near the house, you might prefer organic or low-toxicity controls. Neem oil is effective if used regularly. For chemical control, products containing Lambda-cyhalothrin (like Duduthrin) or Acetamiprid are common in Kenyan agrovets. Always spray in the evening when bees are not active.

Downy Mildew is a fungal disease that appears as a violet-grey mold on the leaves, usually during cold, wet weather. It causes the leaves to collapse. Prevention is better than cure: ensure your crates are spaced out to allow airflow and never water the leaves in the evening. If infection occurs, fungicides containing Metalaxyl or Mancozeb (like Ridomil Gold) are the industry standard for control.

WARNING: Always observe the Pre-Harvest Interval (PHI) indicated on any pesticide bottle. This is the number of days you must wait after spraying before you can eat the produce. For onions, this is crucial for your family’s safety.

SIGNS OF MATURITY AND HARVESTING

How do you know when your crate onions are ready? They will tell you. As the bulb reaches its maximum size, the “neck” of the onion (the part just above the bulb) becomes soft and weak. The leaves will naturally collapse and fall over. This is called “neck fall.” When about 75% of the onions in your crate have toppled over, it is time to harvest.

Stop watering completely about 1-2 weeks before you intend to harvest. This helps the bulb dry out and creates a papery skin, which is essential for storage. To harvest, simply loosen the soil gently and pull the onions out by the leaves. Do not bang them against each other to remove soil, as this bruises them and causes rot.

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CURING: THE SECRET TO LONG SHELF LIFE

You cannot cook the onions immediately after pulling them if you want to store them. They need to “cure.” Curing dries the neck and seals the bulb against bacteria. In a field, farmers leave onions on the ground, but in a crate system, you should move them to a warm, dry, shaded area.

Lay the onions out in a single layer on a wire mesh or a dry sack. Do not pile them up. Keep them there for 2-3 weeks. You will know they are cured when the outer skin is dry and papery, and the neck is completely tight and dry. Only then should you cut off the dried roots and the dried leaves, leaving about an inch of the neck attached. Your onions are now ready for the kitchen or the market.

BUYING SEEDS ONLINE IN KENYA

In the digital age, you don’t need to travel to Nairobi’s River Road to get certified seeds. Several reputable Kenyan agricultural platforms deliver seeds countrywide.

KENYA SEED COMPANY: The state corporation has robust varieties tailored for local climates. While their website is informative, you can often order via their regional stockists or authorized online distributors. https://www.kenyaseed.co.ke/

AGRIJIBU: A comprehensive online agrovet that stocks seeds from Simlaw, Royal Seed, and Syngenta. They offer delivery services across Kenya. https://www.agrijibu.com/

M-SHAMBA: A digital platform connecting farmers to inputs. They verify their suppliers, ensuring you don’t buy fake seeds. https://m-shamba.com/

ROYAL SEED (KENYA HIGHLAND SEED): Known for their premium F1 varieties like Red Pinoy and Jambar. Their website lists authorized distributors, and some third-party platforms stock their full range. https://www.royalseed.co.ke/

SIMLAW SEEDS: You can find their “Online Shop” link on their official website, offering a wide range of vegetable seeds including Red Creole. https://www.simlaw.co.ke/

EXPERT TIP: When buying online, always check for the KEPHIS certification label on the packet image or description. This seal guarantees that the seeds have been tested for germination and purity.

FREQUENTLY ASKED QUESTIONS (FAQ)

Q1: Can I use soil from my backyard for the crates?

Generally, yes, but only if you amend it. Pure backyard soil is often too compact (clay) or too exhausted. You must mix it with well-rotted manure and river sand (3:2:1 ratio) to ensure drainage and fertility. If your soil is very sticky (clay), add more manure and sand.

Q2: How many onions can I grow in one crate?

In a standard milk/bread crate (approx. 60x40cm), you can comfortably grow 15 to 20 onions. This assumes a spacing of roughly 10-12cm between plants. Planting more than this will result in smaller “salad” onions rather than large bulbs.

Q3: My onions are producing flowers. Is this good?

No, this is bad. It’s called “bolting.” When an onion flowers, it sends a hard stalk through the center of the bulb, making it tough and inedible. Bolting is caused by temperature stress (hot days/cold nights) or transplanting seedlings that are too old. Harvest bolting onions immediately and use them; they won’t store well.

Q4: Why are my onion bulbs small?

Small bulbs are usually caused by three things: planting too deep (burying the bulb), lack of sunlight (onions need full sun), or lack of potassium. Ensure your crates are in the sunniest spot possible and use a balanced fertilizer or NPK 17:17:17 during the bulbing stage.

Q5: How often should I water the crates?

Perform the finger test daily. In hot weather (Jan-Mar), you might water daily. In cool weather, maybe 2-3 times a week. The goal is moist, not wet, soil. Inconsistent watering (letting it dry out completely then flooding it) causes the bulbs to split.

Q6: Can I grow spring onions (vitunguu vya majani) in the same way?

Yes, absolutely. In fact, spring onions are easier as they don’t need to form a bulb. You can plant them closer together (5cm spacing) in crates. Varieties like “White Lisbon” are excellent for this.

Q7: How much profit can I make from one crate?

A single crate yields about 2-3 kgs of onions. At a market price of KES 80/kg, that’s KES 240 per crate. It sounds small, but if you have 50 crates, that’s KES 12,000 per harvest from a “waste” space on your roof. The real value is in saving on your grocery bill and having chemical-free food.

Q8: What is the best season to plant onions in crates?

Since you can control water in crates, you can plant year-round. However, the best market prices are usually found between January and April. To hit this window, you should plant your nursery in September/October and transplant in November.

CONCLUSION

Growing bulb onions in crates is more than just a gardening trend; it is a declaration of food independence for the Kenyan urban dweller. It transforms idle concrete spaces into productive, high-yield mini-farms. By following the precise steps of soil mixing, selecting the right F1 varieties like Jambar, and managing your water and nutrients with care, you can harvest professional-quality onions that rival anything found at Marikiti.

The initial effort of sourcing crates and mixing soil is a one-time investment. Once established, your crate farm becomes a renewable asset, producing cycle after cycle of fresh, pungent, and valuable red onions. Start with five crates today, master the water balance, and soon you will be scaling up to cover your entire roof. The soil is ready, the market is waiting-get planting.

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