FoxFarm Grow Big Liquid Concentrate – Gal

FoxFarm Grow Big Liquid Concentrate is a 6-4-4 NPK fertilizer designed for the vegetative stage of plant growth. The one-gallon concentrate blends earthworm castings, Norwegian kelp, and essential micronutrients to build plant size and canopy structure — the foundation for abundant fruit, flower, and bud development when plants move into bloom.

FoxFarm Grow Big Liquid Concentrate Specifications

The table below summarizes the key specifications for the one-gallon size of Grow Big Liquid Concentrate. Values are drawn from the canonical product data and manufacturer documentation.

Specification	Value
Brand	FoxFarm / Hydrofarm
SKU	FX14007
NPK Formula	6-4-4
Volume	1 Gallon (liquid concentrate)
Key Ingredients	Earthworm castings, Norwegian kelp, essential micronutrients
Recommended Application Rate	2 teaspoons per gallon of water, every other watering
Foliar Application	Apply to both sides of leaves; preferred time is early morning
Growth Stage	Vegetative only — discontinue at first sign of flowering
Category	Base Nutrients / Organic
Weight (shipping)	10 lb

Why Choose FoxFarm Grow Big Liquid Concentrate

Grow Big is a vegetative-stage fertilizer, not a general-purpose feed. Its formulation targets the biological needs of plants during the period of rapid leaf and stem expansion — before energy needs to shift toward reproduction. Here is what distinguishes it from basic NPK solutions:

• Organic-derived inputs alongside conventional nutrients. The formula includes earthworm castings and Norwegian kelp — ingredients that contribute trace minerals and biological compounds not always present in purely synthetic vegetative feeds. These inputs support both the plant and the soil food web in amended media.
• Nitrogen-forward ratio for canopy development. The 6-4-4 NPK profile delivers the higher nitrogen proportion that vegetating plants require for chlorophyll production and leaf area expansion. This is the right ratio for plants actively building structure before the transition to bloom.
• Dual application method. Grow Big works as both a soil drench and a foliar spray. Foliar feeding allows nutrients to bypass the root zone entirely, which is useful when roots are stressed, root zones are cold, or growers want faster correction of visible deficiencies during veg.
• Designed to pair with FoxFarm’s complete feeding schedule. Grow Big is one component of FoxFarm’s documented feeding program. Growers who follow the FoxFarm Feeding Schedule use Grow Big through veg and transition to FoxFarm blooming fertilizers at the onset of flowering, creating a planned progression rather than guessing at transitions.
• One-gallon size yields a large volume of working solution. At 2 teaspoons per gallon of water, a single gallon of Grow Big concentrate makes approximately 384 gallons of feed solution — suitable for established commercial or large hobby grows running regular fertigation schedules.

Best Uses for FoxFarm Grow Big Liquid Concentrate

Grow Big is purpose-built for vegetative growth. The following scenarios represent the most appropriate applications based on the product’s documented formulation and use instructions.

• Soil and soilless media — vegetative phase fertigation. Mix 2 teaspoons per gallon of pH-adjusted water and apply every other watering after allowing new transplants a few days to establish. This is the primary intended use — feeding soil-grown plants from seedling establishment through pre-flower.
• Foliar spray to address early deficiencies. When plants show signs of slow growth or pale new growth during veg, foliar feeding with Grow Big delivers nitrogen and micronutrients directly through leaf tissue. Apply to both sides of leaves in the early morning so solution dries before light intensity peaks.
• Coco coir and amended growing media. Grow Big works in non-soil organic and semi-organic substrates where growers supplement base feed with organic inputs. The earthworm castings and kelp components add microbial substrate value to media that benefits from biological activity.
• Greenhouse and outdoor vegetable gardens. The canonical description mentions fruit, flower, and bud development as downstream outcomes — Grow Big supports that trajectory by building robust plant structure during the veg window in any garden environment, including outdoor beds and raised containers.
• Companion use with carbohydrate supplements like Earth Juice Hi-Brix Molasses. In organic soil programs, growers sometimes add molasses-based carbon sources alongside vegetative nitrogen feeds to fuel microbial populations in the root zone. Grow Big’s organic inputs are compatible with this approach.
• Large-scale production grows. The one-gallon concentrate format is appropriate for commercial greenhouse operations or multi-light cultivation spaces where purchasing by the gallon reduces per-application cost compared to smaller sizes.

FoxFarm Grow Big vs Similar Vegetative Fertilizers

When selecting a vegetative base nutrient, growers commonly compare Grow Big against other liquid organic-conventional hybrids available in the market. An alternate supplier listing for Grow Big (SKU FX14007) shows pricing around $109.80, while this listing is available at $103.94 — a meaningful difference for growers buying by the gallon on a regular schedule.

Purely synthetic vegetative nutrients — such as single-part or two-part hydroponic base nutrient solutions — typically deliver precise EC targets without the variability introduced by organic ingredients, but they do not provide the biological inputs (earthworm castings, kelp) that Grow Big includes. Growers running sterile hydroponic systems with inert media (rockwool, hydroton) generally prefer synthetic feeds. Growers running living soil, coco amended with biology, or outdoor beds where microbial health matters tend to get more utility from a product like Grow Big.

Compared to dry organic amendments such as Down to Earth Crab Meal — which releases nutrients slowly through microbial breakdown — Grow Big is immediately plant-available in liquid form. This makes it more suitable for container grows with shorter veg cycles where waiting for slow-release amendments to become available is not practical. Dry amendments and liquid concentrates can be used in combination, with dry amendments incorporated at transplant and liquids applied during fertigation.

Growers exploring root zone biology enhancement during veg may also consider dedicated microbial inoculants such as Advanced Nutrients Tarantula as a companion product alongside Grow Big, rather than as a direct substitute. These products address different plant needs and are generally complementary rather than competing.

Compatibility

Grow Big is compatible with a broad range of growing environments during the vegetative stage. The following notes are based on the product’s documented use cases and formulation type.

• Soil and amended growing media. Grow Big is designed for soil-based systems. The earthworm casting and kelp inputs interact beneficially with active microbial populations in amended soils. It is also compatible with soilless amended mixes such as peat- and coco-based media that have been inoculated with beneficial organisms.
• Coco coir systems. The product can be applied to plants grown in coco coir as a supplemental organic input alongside a primary coco base nutrient. Growers should monitor EC to avoid over-application when combining multiple nutrient sources.
• Foliar spray equipment. Grow Big is suitable for use in standard hand sprayers and backpack sprayers when prepared as a foliar solution. No special equipment is required beyond what is used for standard foliar programs.
• FoxFarm feeding programs. Grow Big is explicitly designed to integrate with FoxFarm’s published Feeding Schedule. At the first sign of flowering, the schedule calls for transitioning to FoxFarm bloom-stage fertilizers. Following the complete schedule as published provides the clearest guidance for transitions between growth stages.
• Not formulated for sterile hydroponic recirculating systems. Because Grow Big contains organic-derived ingredients (earthworm castings, kelp), it is not ideal for sterile recirculating deep water culture (DWC) or nutrient film technique (NFT) systems where organic particulates can introduce pathogens or clog drip emitters. It is better suited to drain-to-waste soil and coco applications.

Dosing Guidelines

The dosing instructions below are sourced directly from the canonical product description. Always start at the lower end of application rates with new plantings and adjust based on plant response.

• Standard soil drench rate: 2 teaspoons (approximately 10 mL) per gallon of water. Apply every other time you water — not at every watering — to avoid nutrient accumulation in the root zone.
• New plantings: Allow newly transplanted seedlings or cuttings a few days to settle into their growing media before beginning Grow Big applications. Starting feeds too early on stressed transplants can cause fertilizer burn or slow establishment.
• Foliar feeding rate: Dilute at the standard 2 teaspoons per gallon rate and apply to both sides of leaves. Foliar feeding is most effective when done early in the morning, allowing the solution to be absorbed before midday heat causes rapid evaporation or tip burn.
• Transition to bloom: At the first sign of flower development (pistil formation in cannabis, flower bud formation in fruiting crops), discontinue Grow Big and switch to a FoxFarm bloom-stage fertilizer. Continuing high-nitrogen vegetative feeds into bloom delays the shift in plant energy allocation toward flower production.
• FoxFarm Feeding Schedule: For growers running the complete FoxFarm program, refer to the published FoxFarm Feeding Schedule for week-by-week rate adjustments and product transition timing. The feeding schedule accounts for the combination of multiple FoxFarm products used across the full crop cycle.

EC targets and pH ranges are not published in the canonical product data. As a general practice for liquid organic fertilizers in soil and coco, maintain water pH between 6.0 and 6.8 for soil applications and 5.8 to 6.3 for coco-based media.

How to Use FoxFarm Grow Big Liquid Concentrate

1. Allow transplants to establish. If you have just transplanted seedlings or rooted cuttings, wait two to three days before beginning any fertilizer applications. This settling period allows roots to begin exploring new media without the added stress of fertilizer salts.
2. Measure the concentrate. Shake the Grow Big bottle before measuring. Use a calibrated measuring spoon or syringe to measure 2 teaspoons (approximately 10 mL) of concentrate per gallon of feed water.
3. Add to pH-adjusted water. Fill your reservoir or watering container with the appropriate volume of clean water. Adjust pH to your target range before adding concentrate (approximately 6.0–6.8 for soil; 5.8–6.3 for coco). Add the Grow Big concentrate and stir thoroughly.
4. Verify pH after mixing. Adding the nutrient concentrate may shift pH slightly. Re-check and adjust if necessary before application.
5. Apply every other watering. Water plants with plain, pH-adjusted water on the off cycles. This practice prevents nutrient accumulation and salt buildup in the root zone between feedings.
6. For foliar feeding: Prepare the same 2 teaspoon per gallon solution in a clean sprayer. Apply to both sides of all leaves in the early morning hours. Allow foliage to dry completely before lights-on or before full sun exposure outdoors.
7. Monitor plants and adjust. Observe new growth weekly. Pale, slow-developing leaves may indicate insufficient nitrogen. Dark, clawing leaves or tip burn may indicate overfeeding. Adjust dose up or down in small increments based on what you observe.
8. Transition at the onset of flowering. As soon as flowering indicators appear, stop Grow Big applications and introduce your chosen FoxFarm bloom fertilizer according to the FoxFarm Feeding Schedule.

Sources & Further Reading