The Source Gro A&B – Vegetative Stage Nutrients

A Two-Part Grow Feed With Amino, Fulvic and Humic Acids

The Source Gro A&B is the two-part base nutrient for the growth and vegetative stage in The Source range, sold as a matched Part A and Part B set. Gro A has an NPK of 5-0-2 and Gro B an NPK of 1.2-2-4, with Part B carrying the trace elements zinc, boron, copper, cobalt, molybdenum and EDTA-chelated manganese. Both parts add amino acids, fulvic acids, natural humic acids, vitamins, sugars and natural stress-relieving agents, and Gro A includes natural plant-extract growth hormones, with no artificial plant growth regulators. It was designed for AutoPot Watering Systems but suits every hydroponic feeding method, in soil, coco or hydro, on hard or soft water, and gives relentless, even growth that sets plants up for flowering.

Key Benefits

• Balanced two-part feed — Gro A 5-0-2 and Gro B 1.2-2-4, mixed in equal amounts.
• Organic acids built in — amino, fulvic and humic acids, vitamins and sugars support root development and nutrient uptake.
• Full trace-element package — zinc, boron, copper, cobalt, molybdenum and chelated manganese in Part B.
• Stress-relieving agents — help plants hold steady through heat and transplanting.
• Economical — full strength is just 1 ml of each part per litre.
• Any medium, any water — soil, coco and hydro; hard or soft water.

Slow, Uneven Vegetative Growth

Too weak a feed in veg gives pale, slow plants; too strong and young roots scorch. Gro is dosed by EC: equal parts of A and B into the water until you hit a gentle EC for young plants, raised as they grow, so vegetative growth stays fast and uniform and plants go into flowering with strong structure and healthy roots. The vegetative stage can run as long as you need, though the maker advises not switching to flowering before week two.

How to Use

• Mixing: add equal amounts of Part A and Part B to the water, stirring between parts, until you reach your target EC. Measure your plain water first; tap water usually reads between 0.1 and 0.8 EC.
• EC: keep young plants low at about 1.0–1.4 EC, rising to 1.7–2.4 EC as they grow, per The Source's guidance.
• Stimulators after: add Origin, Delta, Elements or Alluvium once A and B are in; EC will rise by about 0.4–0.7, which is expected.
• Soil and compost (AutoPot and greenhouse charts): 0.25 ml of each part per litre for weeks one and two, 0.5 ml for weeks three and four, then 1 ml from week five (label range 0.25–1 ml).
• Coco and hydro, and any medium on hand watering, drip, NFT or flood and drain: 0.5 ml of each part per litre for weeks one and two, then 1 ml from week three (label range 0.5–1 ml for coco and hydro).
• Moving to flowering: switch to The Source Flo A&B when the growth stage is complete.
• pH: set the reservoir to about pH 5.8 for soil and compost and about pH 5.6 for coco or rockwool, as The Source recommends.

Frequently Asked Questions

Works Well With

Bluelab Nutrient TruncheonDoses A and B to your target EC Bluelab pH PenChecks pH once the feed is mixed AutoPot SystemThe gravity-fed pots Gro was designed for