For most gardeners, TPS Nutrients Liquid Onion Fertilizer, 32 fl oz is my best overall pick because its larger liquid format suits regular feeding across an onion bed. Old Cobblers Farm Wicked Growth Garlic and Onion Fertilizer stands out for gardeners who want a product aimed at several bulb crops, while Prevegenics Onion Fertilizer, 32 fl oz offers another dedicated liquid option to compare. The main tradeoff is between liquid concentrates that are easy to portion and larger or solid-format products that may better suit broad, repeated use. Pack size, label directions, and whether you grow onions alongside garlic, shallots, or leeks all affect the right choice. Read on for the full breakdown and a guide to matching a fertilizer to your garden.
Get garden gear delivered free with Prime
- Fast, free delivery on millions of items
- Prime Video, Amazon Music and more included
- Member-only deals all year
Complete the kit
Key Takeaways
- The 32 fl oz TPS Nutrients liquid is my overall pick for gardeners seeking a larger-format onion-specific fertilizer; the 8 fl oz version suits a smaller trial or a limited planting more closely.
- Old Cobblers Farm is the lineup’s multi-crop option, with a garlic-and-onion focus that also names shallots and leeks; its 20 lb format is a different scale of purchase from the smaller product listing.
- Liquid format is a practical advantage, not a guarantee of better results. Mixing and application depend on the label directions, so compare instructions before choosing between concentrates.
- Pack size changes the value calculation. A larger container can make sense for a sizable bed or repeat use, while a small bottle can reduce leftover product for a few containers or a short row.
- Product specialization varies. The TPS and Prevegenics listings are onion-focused, while Wicked Growth explicitly covers several bulb crops; choose based on what you grow, not the broadest label alone.
| onion fertilizer | Brand | Form | Target plants | Volume |
|---|---|---|---|---|
| TPS Nutrients Liquid Onion Fer | TPS Nutrients | Liquid | Onions and other alliums | 32 fl oz |
| Old Cobblers Farm Wicked Growt | Old Cobblers Farm | Granular | Onions, garlic, shallots, leeks, and chives | — |
| TPS Nutrients Liquid Onion Fer | TPS Nutrients | Liquid | Onions, garlic, and other alliums | 8 fl oz |
| Old Cobblers Farm Wicked Growt | Old Cobblers Farm | Granules | Garlic, onions, shallots, leeks, and chives | — |
| Prevegenics Onion Fertilizer | Prevegenics | Liquid | — | 32 fl oz |
| Gardenera Liquid Power Onion F | Gardenera | — | — | — |
More Details on Our Top Picks
TPS Nutrients Liquid Onion Fertilizer, 32 fl oz
The larger TPS liquid bottle suits growers who want an onion-focused feed they can apply to garden beds, raised beds, or containers with a watering can or sprayer. Its allium-specific positioning makes it a more targeted choice than a general-purpose plant food, while the liquid format can fit into a regular watering routine. Compared with the 8 fl oz TPS Nutrients Liquid Onion Fertilizer, this size offers more product for ongoing use across a larger planting. The tradeoff is that the supplied details give no nutrient analysis or dilution instructions, so buyers have less information for planning feed strength and frequency. I’d choose it for application flexibility, but favor the smaller TPS bottle if its stated mixing ratio is a priority.
Pros:- Formulated for onions and other alliums
- Liquid format works with a watering can or sprayer
- Suitable for garden beds, raised beds, and containers
Cons:- Supplied details do not include a nutrient analysis
- No dilution instructions are provided in the supplied details
- Requires mixing or application equipment rather than direct granular placement
Best for: Gardeners feeding onions and other alliums across beds, raised beds, or containers who want a larger liquid bottle and flexible watering-can or sprayer application.
Not ideal for: Growers who need a published nutrient analysis or exact mixing directions to plan a measured feeding schedule.
- Brand:TPS Nutrients
- Form:Liquid
- Volume:32 fl oz
- Target plants:Onions and other alliums
- Application method:Watering can or sprayer
- Suitable growing areas:Garden beds, raised beds, and containers
- Made in:USA
Our verdict“Choose this larger TPS bottle for flexible liquid application across several allium planting areas, but pick the 8 fl oz version if you want a stated mixing ratio.”
Old Cobblers Farm Wicked Growth Garlic and Onion Fertilizer, Bulb Crop Plant Food for Onions, Shallots and Leeks
Wicked Growth’s 5-10-10 formula is the most explicit nutrient option here for growers who want a granular allium fertilizer with a stated analysis. Its 3% sulfur, calcium, boron, and zinc distinguish it from liquid picks such as Prevegenics Onion Fertilizer, whose supplied details describe a blend but do not list exact nutrient percentages. The pre-plant and side-dress directions also suit gardeners who plan feeding around planting and bulb growth. That specificity comes with more hands-on work: the granules need measured application, should stay off foliage and bulb shoulders, and the product information advises careful rate calculation and soil testing. I’d favor it over the TPS liquids when a defined NPK ratio matters, but skip it if you want a simple feed mixed into routine watering.
Pros:- Published 5-10-10 NPK analysis
- Includes 3% sulfur, calcium, boron, and zinc
- Formulated for onions, garlic, shallots, leeks, and chives
- Provides pre-plant and side-dress application rates
Cons:- Requires careful rate calculation and soil testing to avoid over-application
- Granules must be kept off foliage and bulb shoulders
- Less convenient than liquid fertilizers for mixing into routine watering
Best for: Allium growers who want a granular fertilizer with a published 5-10-10 analysis, sulfur, and directions for pre-plant and side-dress feeding.
Not ideal for: Container gardeners or beginners seeking an easy liquid feed, especially if they do not want to measure granules or manage soil-based application rates.
- Brand:Old Cobblers Farm
- Form:Granular
- Weight:5 lb
- NPK ratio:5-10-10
- Sulfur content:3%
- Calcium:2%
- Micronutrients:Boron and zinc
- Application rate:1/2 to 1 cup per 10 sq ft pre-plant; 1/2 cup per 10 linear ft for side-dressing
- Target plants:Onions, garlic, shallots, leeks, and chives
Our verdict“Pick Wicked Growth if a defined granular analysis and broad allium coverage matter more to you than the simpler application of a liquid fertilizer.”
TPS Nutrients Liquid Onion Fertilizer, 8 fl oz
This 8 fl oz TPS bottle is the most compact option for gardeners feeding a modest onion patch or a few allium containers. Its stated mix of 1 tablespoon per gallon of water gives buyers clearer use directions than the larger TPS bottle, whose supplied details omit a dilution ratio. It targets onions, garlic, and other alliums, so it offers broader crop relevance than Prevegenics Onion Fertilizer, which is described for onion growth specifically. The small size is also its main limitation: larger beds or repeated feeding can use up the bottle sooner, and the supplied product information lists no nutrient analysis. I’d choose it for a small planting where measured liquid application matters, but the 32 fl oz TPS bottle makes more sense when volume is the priority.
Pros:- Formulated for onions, garlic, and other alliums
- Provides a clear mixing ratio of 1 tablespoon per gallon
- Suitable for garden beds, raised beds, and containers
Cons:- Small 8 fl oz volume may not suit larger plantings
- Requires dilution before application
- Supplied details do not provide a nutrient analysis
Best for: Small-space gardeners and container growers feeding a limited number of onion, garlic, or other allium plants who want a stated dilution ratio.
Not ideal for: Gardeners with large beds or season-long feeding needs who want a larger supply or a disclosed nutrient analysis.
- Brand:TPS Nutrients
- Form:Liquid
- Volume:8 fl oz
- Target plants:Onions, garlic, and other alliums
- Mixing ratio:1 tablespoon per gallon of water
- Suitable growing areas:Garden beds, raised beds, and containers
- Country of manufacture:USA
Our verdict“Choose this compact TPS option for a small allium planting and clear dilution directions; choose the 32 fl oz TPS bottle for a larger supply.”
Old Cobblers Farm Wicked Growth Garlic and Onion Fertilizer, 20 lb
The large-format Wicked Growth listing is aimed at growers managing substantial allium beds who want a granular feed for pre-plant use and side-dressing. Its stated 5-10-10 analysis, 3% sulfur, calcium, boron, and zinc match the nutrient profile of the 5 lb Wicked Growth option, but the larger title weight could make it a better fit for covering more ground. There is, however, a major purchasing ambiguity: the title says 20 lb while item details say 5 lb. I would verify the delivered weight before choosing it over the 5 lb listing, which has a consistent stated weight. This fertilizer also needs measured placement and timed feeding, including stopping 2 to 3 weeks before harvest, so it is less hands-off than the liquid TPS options.
Pros:- Formulated for onions, garlic, shallots, leeks, chives, and other alliums
- Lists 5-10-10 nutrients with 3% sulfur and 2% calcium
- Includes boron and zinc
- Provides pre-plant and side-dress rates plus a stop-feeding window
Cons:- Weight is inconsistent: title says 20 lb while item details say 5 lb
- Requires measured granular application and careful timing
- Must stop feeding 2 to 3 weeks before harvest
Best for: Experienced growers with large onion or mixed-allium beds who want granular pre-plant and side-dress feeding and can confirm the package weight before purchase.
Not ideal for: Buyers who need a reliable stated package quantity, small-space gardeners, or anyone seeking a low-handling liquid fertilizer.
- Brand:Old Cobblers Farm
- Model number:WG-5-10-10
- Form:Granules
- Weight:20 lb in title; 5 lb in item details
- Nutrient analysis:5% ammoniacal nitrogen, 10% phosphate, 10% potash
- Additional nutrients:3% sulfur, 2% calcium, boron, and zinc
- Target plants:Garlic, onions, shallots, leeks, and chives
- Application rate:1/2 to 1 cup per 10 sq ft before planting; 1/2 cup per 10 linear ft for side-dressing
- Pack count:1
Our verdict“Consider this large-format Wicked Growth listing for a substantial allium garden only after confirming its actual package weight.”
Prevegenics Onion Fertilizer – 32 fl oz
Prevegenics Onion Fertilizer pairs a 32 fl oz liquid format with a clearly stated 1:3 dilution ratio, making it a practical choice for onion growers who want a defined mixing step without handling granules. Its listed blend of macronutrients and micronutrients is positioned around plant vigor and onion growth, though the supplied details do not give an exact NPK analysis. That leaves less formulation detail than the 5-10-10 Old Cobblers Farm Wicked Growth fertilizers, which also cover more allium types. Prevegenics is the more focused pick for Allium cepa, but that specialization limits its appeal if you also feed garlic, leeks, or other crops. I’d choose it for a dedicated onion planting and pick a broader allium formula for a mixed bed.
Pros:- Liquid format offers a straightforward alternative to granular feeding
- Provides a clear dilution ratio of 1 part fertilizer to 3 parts water
- Described as containing macronutrients and micronutrients
- Identifies onion as the target species
Cons:- Designed specifically for onions and may not suit other crops
- Supplied details do not list exact NPK percentages
- Requires dilution before application
Best for: Onion gardeners who want a 32 fl oz liquid feed, a stated dilution ratio, and a formula identified for Allium cepa.
Not ideal for: Growers feeding garlic, leeks, or mixed crops who prefer a fertilizer explicitly listed for several allium types or need a published NPK breakdown.
- Brand:Prevegenics
- Form:Liquid
- Volume:32 fl oz
- Target species:Allium cepa
- Mixing ratio:1 part fertilizer to 3 parts water
- Nutrient blend:Macronutrients and micronutrients
- Manufacturer:Prevegenics LLC
- Part number:OBF-32O
Our verdict“Choose Prevegenics for a clearly diluted liquid feed focused on onions, but favor Wicked Growth if you want a stated NPK ratio and wider allium coverage.”
Gardenera Liquid Power Onion Fertilizer Concentrate, 8 fl oz
Gardenera’s onion-specific formula makes this a focused pick for growers who want a liquid concentrate for containers or a modest garden bed. It is described as supporting roots, bulb development, and upright foliage, while chelated micronutrients are intended to help nutrients remain available in soil. Compared with TPS Nutrients Liquid Onion Fertilizer, 32 fl oz, this bottle contains less product, so it suits smaller planting areas better than repeated or broad-scale applications. The tradeoff is its approximately 1.69 pH: that is highly acidic, calling for careful handling and clear dilution guidance before use. The listed 3:1:2 mixing ratio may also leave questions about exact preparation, so buyers who want straightforward instructions may prefer a product with more explicit directions.
Pros:- Formulated specifically for onions rather than general garden feeding
- Designed to support both root growth and bulb development
- Includes chelated micronutrients intended to improve nutrient availability
- Liquid format is suitable for pots as well as garden plots
Cons:- Very acidic listed pH calls for careful handling and dilution
- The 3:1:2 mixing ratio may need clarification before application
- Eight fluid ounces may be insufficient for larger plantings or frequent feeding
Best for: Container growers and gardeners feeding a small onion patch who want a liquid product formulated specifically for onions.
Not ideal for: Growers with large beds or anyone who prefers forgiving, clearly specified mixing instructions; the small bottle and very acidic formula may be inconvenient.
- Brand:Gardenera
- Product form:Liquid
- Specific use:Onions
- Liquid volume:8 fl oz
- Item weight:4 oz
- Mixing ratio:3:1:2
- pH:Approximately 1.69
- Number of items:1
Our verdict“Choose Gardenera for a small onion planting if you want a crop-specific liquid concentrate and are comfortable checking its dilution instructions carefully.”
How We Picked
I compared the six listings by crop focus, format, and pack size—the details that most directly affect an onion grower’s purchase. I also weighed how readily each option appears to fit different garden scales and routines, from a small planting to repeated feeding across a larger bed. Product names and stated formats inform this comparison; I do not assume unprovided nutrient ratios, application rates, or performance claims.
The ranking favors practical fit and clarity over sheer container size. The 32 fl oz TPS option leads as a straightforward larger-format onion-specific liquid, while Wicked Growth earns a distinct place for its stated use across several bulb crops. Smaller bottles rank as better fits for limited needs rather than automatically weaker fertilizers, and Prevegenics remains a dedicated liquid alternative. I treat the 20 lb Wicked Growth listing as a scale choice, not proof of superior results; buyers should verify directions and coverage on each label before comparing how much product they need.
| onion fertilizer | Brand | Form | Target plants |
|---|---|---|---|
| TPS Nutrients Liquid Onion Fer | TPS Nutrients | Liquid | Onions and other alliums |
| Old Cobblers Farm Wicked Growt | Old Cobblers Farm | Granular | Onions, garlic, shallots, leeks, and chives |
| TPS Nutrients Liquid Onion Fer | TPS Nutrients | Liquid | Onions, garlic, and other alliums |
| Old Cobblers Farm Wicked Growt | Old Cobblers Farm | Granules | Garlic, onions, shallots, leeks, and chives |
| Prevegenics Onion Fertilizer | Prevegenics | Liquid | — |
| Gardenera Liquid Power Onion F | Gardenera | — | — |
Factors to Consider When Choosing Best Onion Fertilizers
Before choosing, match the fertilizer to your planting scale, crop mix, and application habits. The right package can reduce waste and make feeding easier, but no product format can replace following the label and responding to your soil and plants.
Match Package Size to Your Planting
Estimate how many onions you plan to feed and how often the label calls for application before buying a large container. A small bottle can be a sensible starting point for a few containers or a short row, even if its upfront package seems less convenient. Larger packs suit gardeners who expect repeated use or have more ground to cover, but unused fertilizer can sit in storage. Check storage guidance and the product’s usable life rather than assuming a bigger package is automatically better value. My rule is to buy for the planting you actually maintain, not a garden you might expand later.
Read the Application Directions Before Comparing Formats
Liquid concentrates and dry fertilizers can call for different preparation and application routines, so compare the instructions rather than judging by format alone. Look for how the product is measured, whether it is diluted, and how often it is applied. A concentrate may be convenient to portion, but measuring errors can lead to using more or less than directed. Dry products may suit gardeners who prefer handling a solid amendment, yet still require careful label-based application. Choose the method that fits your routine and equipment, then follow the stated rate rather than improvising.
Choose for the Crops You Actually Grow
An onion-focused label may be the most direct fit for a garden devoted to onions, while a product naming garlic, shallots, and leeks may suit a mixed bulb-crop bed. Shared crop language does not mean every plant has identical needs or application timing. Read the label for the crops and directions it specifically covers, especially if you plan to use one fertilizer across several species. Avoid buying a broader-use product solely because it names more crops; unused versatility does not help if the package or routine is a poor fit. Crop focus is most useful when it matches what is already in your garden.
Use Soil and Plant Needs to Guide Feeding
Fertilizer choice should follow the condition of the growing area, not the assumption that every onion bed needs the same feeding. A soil test can help identify existing nutrient levels and reduce the risk of adding nutrients your soil already has. Consider the garden’s history, including recent compost or fertilizer applications, before layering on another product. Follow the product label and local growing guidance for timing, since excess or poorly timed feeding can work against your goals. If plants look weak, check water, light, spacing, and pests as well as nutrition instead of responding with extra fertilizer alone.
Decide When a Larger Pack Is Worth It
A larger package makes most sense when the label’s directions and your planting area point to regular use of the product. Compare the amount required per application and the number of applications listed, rather than comparing bottle or bag size in isolation. The 32 fl oz liquids and the 20 lb dry listing in this roundup represent different formats and scales, so their package sizes are not directly interchangeable. Storage space, lifting, measuring, and the chance of leftover product all belong in the decision. For a first season with an unfamiliar fertilizer, a smaller pack can limit commitment while you learn whether its routine suits your garden.
Keep Feeding Consistent and Avoid Overapplication
More fertilizer does not automatically mean larger or healthier bulbs, and exceeding directions can create problems rather than solve them. Use the label’s stated rate and schedule, and keep notes on application dates so repeated feeds do not accidentally overlap. Apply consistently across the planting instead of concentrating product around a few plants. If growth changes, assess moisture, soil conditions, and other possible causes before increasing the dose. A simple routine that you can follow accurately is often a better fit than a complicated program with several overlapping products.
Frequently Asked Questions
Should I choose the 32 fl oz TPS bottle or the 8 fl oz version?
Choose based on the area you intend to feed and the label’s stated application rate, not bottle size alone. The 32 fl oz listing makes more sense when you expect repeated use or have a larger planting, while the 8 fl oz version can suit a small bed, containers, or a first purchase. Compare the directions and storage guidance for the exact product before deciding. If you are unsure how much your garden will require, starting with a smaller amount can limit leftover product.
Can I use a garlic-and-onion fertilizer on shallots and leeks too?
Wicked Growth’s product name specifically includes onions, shallots, and leeks, but the label remains the authority on approved crops and application directions. Check that it names the plants you intend to feed and follow any crop-specific instructions. Do not assume that a shared bulb-crop label means the same rate or schedule is suitable for every plant. If you grow several crops together, apply carefully so each receives only the amount directed for its use.
Is liquid fertilizer a better choice than a 20 lb dry product for onions?
Neither format is automatically better; the better fit depends on how you prefer to measure and apply fertilizer and how much garden you need to cover. Liquids can suit gardeners comfortable with mixing or portioning concentrate, while a dry product may fit a different handling routine and larger-scale use. Compare the label’s application method, rate, and storage instructions before choosing. The 20 lb package is a larger-format option, but package size alone does not establish coverage or performance.
Do I need a specialized onion fertilizer if I already use compost?
Not necessarily. Compost adds organic matter and may contribute nutrients, but its nutrient content can vary, so it does not by itself tell you whether your soil needs more fertilizer. A soil test can clarify what is already available and help prevent unnecessary applications. If you add a fertilizer, follow its label and account for other amendments you have used. For a modest planting in fertile soil, checking conditions first may be more useful than adding another product by habit.
How do I choose an onion fertilizer for a small container garden?
For a small container planting, focus on clear directions, manageable package size, and whether the label covers the crop and growing setup you have. A smaller bottle, such as one of the 8 fl oz options in this roundup, can reduce the chance of keeping more fertilizer than you need. Measure carefully because a small volume of growing medium can be affected by overapplication. Follow the label’s instructions for container use rather than adapting a rate meant for a garden bed.
Conclusion
My best overall pick is TPS Nutrients Liquid Onion Fertilizer, 32 fl oz for gardeners who want an onion-specific liquid in a larger format. For best value by practical fit, I’d choose the 8 fl oz TPS bottle when a smaller planting makes a large container unnecessary; the right value depends on how much you will use. Best for beginners is also the smaller TPS option if you want to start with a limited amount and can follow its label directions. For best for mixed bulb-crop needs, Wicked Growth is the clearest match because its listing names garlic, onions, shallots, and leeks; the 20 lb version suits buyers who have a larger-scale reason for that package size. Best premium-style alternative is Prevegenics Onion Fertilizer, 32 fl oz, for shoppers comparing another larger-format, onion-focused liquid. Choose by crop list, directions, and garden scale, then apply only as the product label instructs.
Columbus Day / Indigenous Peoples' Day Picks
long weekend sales
As an affiliate, we earn on qualifying purchases.
