Terra Grow Dosage Guide: Soil and Hydro Mix Steps

Plagron Terra Grow is a soil-based base nutrient for the vegetative (grow) phase, and the correct starting dosage is 5 mL per litre of water (roughly 20 mL per gallon) as a maximum. In practice you work up to that over the first few weeks, starting much lower, while targeting an EC of around 0.6 mS/cm in early weeks and climbing to 2.0 mS/cm at peak veg. pH for your feed water should sit in the 5.5 to 6.5 range. That is the core answer, but how you get there depends on your grow style, your tap water, and which week you are in. Here is exactly how to dial it in.

Which "Terra Grow" bottle are you actually holding?

Before dosing anything, confirm you have the right product. "Terra Grow" from Plagron is a single-part base nutrient designed specifically for the grow (vegetative) phase when growing in soil or a soil-like substrate. It is not the same as Plagron's hydro line (Hydro A/B), their organic lines, or any grow-phase additive from another brand that might share a similar name. Check your bottle label for the Plagron logo and the phrase "Base Nutrient" or "complete nutrient for the grow phase." If your bottle says something like "Terra Bloom" or "Terra Vega" from a different manufacturer, or if you are running a two-part hydro system, you are working with different dosage guidelines entirely.

Terra Grow is also specifically a mineral (synthetic) nutrient, which matters because Plagron's own guidance notes that organic products generally don't require strict EC and pH management, but mineral products like Terra Grow absolutely do. So if you have this bottle in hand, you need a pH meter and an EC/TDS meter. No exceptions.

Soil vs. hydro: what changes and what doesn't

Terra Grow is formulated and labeled for soil (and similar substrates like coco mixed with soil). It is not Plagron's recommended product for recirculating hydro systems, where the Hydro A/B line is the proper fit. That said, plenty of growers use Terra Grow in a drain-to-waste coco or amended media setup, and it works well there. The key differences between soil and a more hydro-style setup come down to buffering and frequency.

The practical upshot: in soil, the medium gives you some forgiveness if your EC creeps a little high. In coco or any near-inert setup, that buffer is gone, so small dosing errors show up faster as tip burn or lockout. Adjust your expectations (and your measuring habits) accordingly. If you are wondering what to grow while dialing in your Terra Grow feed for vegetative phase, start with easy, fast-germinating plants that match your schedule Adjust your expectations.

Dosing by stage: seedling through veg and into flower prep

Plagron's official 100% Terra grow schedule gives you week-by-week EC targets that include your tap water's baseline EC (assumed at 0.4 mS/cm in their chart). If your tap water reads differently, adjust: your nutrient-contributed EC equals the target EC minus your tap water EC. Here is how the stages break down.

Seedling and early veg (weeks 1–3)

Target total EC: 0.6 mS/cm. With tap water at 0.4, that means you are only adding around 0.2 mS/cm worth of nutrient, which is a very light feed. At this stage roots are fragile and the plant's demand is low. Start with roughly 1–2 mL/L of Terra Grow rather than the full 5 mL/L. Mix your solution, check EC, and nudge the dose up or down to hit that 0.6 mS/cm target. If your tap water already reads 0.6 or above, plain water (or very lightly supplemented water) may be all you need for the first couple of weeks.

Active veg (weeks 4–7)

This is where you ramp up progressively. The official schedule moves from 1.6 mS/cm at weeks 4–5, to 1.8 at week 6, and 1.9 at week 7. Your dose of Terra Grow increases toward the 5 mL/L maximum during this window. Increase in small steps (0.5–1 mL/L at a time per watering cycle) and always verify EC after mixing rather than just trusting a volume measurement. Watch the plants between each step: healthy new growth, deep green color, and no tip issues means you're in range.

Peak veg and transition (weeks 8–10)

Target EC climbs to 2.0 mS/cm and holds there. At this point you are likely at or near the 5 mL/L maximum. If you are growing photoperiod plants and approaching the flip to flower, week 11 in the schedule is water-only as a transitional flush before switching to a bloom nutrient. If you are growing autoflowers, watch the plants for signs of pre-flowering and begin reducing Terra Grow while transitioning to your bloom product.

These mL/L figures are approximations because your tap water EC and room temperature will shift results. Always measure, never assume.

How to actually mix a feed: step by step

Mixing order and water quality matter more than most growers realize. Getting this wrong causes nutrient precipitation (cloudy solution, locked-out minerals) even before the plant sees it.

1. Start with your water at room temperature (roughly 18–22°C). Cold water slows dissolution; very warm water speeds microbial growth. Temperature compensation on your pH meter should be set or noted because pH readings shift with temperature.
2. If you use a silica supplement, add it first and stir well before anything else. Silica has a high pH and must be dispersed before adding other nutrients or it will bind them.
3. Add Terra Grow to the water (not water to the concentrate). Measure using a graduated syringe or pipette, not a kitchen spoon. Start with slightly less than your target dose so you have room to fine-tune.
4. If you use a cal-mag supplement or any other additive, add it now and stir.
5. Stir the solution thoroughly for 30–60 seconds and let it sit for 2–3 minutes.
6. Measure EC/TDS. Compare to your stage target. If EC is low, add a small additional amount of Terra Grow and re-measure. If it is already at or above target, do not add more.
7. Adjust pH last. For soil use, target 5.8–6.5. For coco/near-inert, target 5.5–6.2. Use a pH up or down solution in small drops, stir, and re-measure. Repeat until stable.
8. Re-check EC after pH adjustment, as pH adjusters can slightly shift EC readings.

Water quality is worth a quick note. If your tap water EC is high (above 0.6–0.7 mS/cm on its own) you are already close to or at the early-veg target before adding anything. In that case, either use filtered or RO water and build from a clean baseline, or reduce your Terra Grow dose significantly and re-verify EC. Plagron's official schedule assumes 0.4 mS/cm tap water, so factor in any deviation from that.

Diagnosing and fixing the most common dosage problems

Nutrient burn (overfeeding)

Classic signs are yellowing or brown crispy tips on otherwise healthy leaves, starting at the tips of lower or older fan leaves and progressing inward if it continues. In soil, this can also show up as a white salt crust on the topsoil. The fix is straightforward: check your EC. If it is above the target for the current week, dilute your next feed or give a plain-water watering to let the medium buffer down. Do not add more nutrients until the plant looks stable. Going forward, do not dose by volume alone; always verify with an EC meter before feeding.

Underfeeding and pale or slow growth

If new growth is light green or yellow (especially uniform yellowing across the whole canopy rather than spotty), leaves are small, and internodal spacing is tight but growth is slow, you are likely underfeeding or your EC is too low. Check EC: if it is well below target for the week, step up your dose. Also check that pH is not drifting outside the 5.5–6.5 window, because even a correctly dosed feed becomes unavailable if pH is off. Pale growth with correct EC but wrong pH is a lockout problem, not a dosage problem.

pH drift causing apparent deficiencies

One of the most common mistakes growers make is adjusting pH before adding nutrients, rather than after. Adding Terra Grow changes the pH of your solution, so any pH adjustment you made before adding it is now irrelevant. Always add nutrients first, then adjust pH. If you notice spotty discoloration, purpling on stems, or weird color patterns that do not match a clean deficiency, check your pH meter calibration first. Calibrate with fresh buffer solutions (7.0 and 4.0 are the standard two-point calibration for a nutrient solution range), then re-measure your solution.

Salt buildup in the medium

In soil, if you have been feeding at full strength for multiple weeks without any plain-water flushes, salt accumulation can raise the root-zone EC above what you are delivering in your feed water. Signs include progressively worsening tip burn even though your feed EC looks correct, or sudden wilting that does not respond to watering. Flush with plain pH-adjusted water (roughly 3x the pot volume) and measure runoff EC. If runoff EC is significantly higher than your feed EC, flush until runoff EC is close to feed EC before resuming normal feeding.

Your application schedule: how often, runoff, and system type

Drain-to-waste (most common for soil and coco)

In a drain-to-waste setup you water until you get 10–20% runoff from the bottom of the pot. This runoff is discarded. Checking the EC and pH of runoff is extremely useful: runoff EC should be within roughly 0.3–0.5 mS/cm of your feed EC. If runoff EC is much higher, you have salt buildup and need a flush. If it is much lower, the medium may be depleted. In soil, a common cadence is feeding every other watering (one nutrient feed, one plain pH-adjusted water), but this varies with plant size, pot size, ambient temperature, and growth rate. In coco, most growers feed with nutrients every watering once the plant is established.

Recirculating systems

As noted earlier, Terra Grow is not specifically designed for recirculating hydro systems, and Plagron's Hydro A/B line is the appropriate product for those setups. If you are trying to do this in the spirit of Valerian grow best harry potter, follow the same EC and pH discipline rather than guessing Terra Grow. If you are running recirculation with Terra Grow by choice, test your reservoir EC and pH daily. Reservoir EC drifts as plants consume nutrients and water evaporates. Top off with plain water when level drops (to compensate for evaporation-driven EC rise), and do full reservoir changes every 7–10 days to prevent salt and pathogen buildup. Never just keep topping up with fresh nutrient solution without knowing your current EC, or you will overfeed progressively.

Flush week and transition

Following the Plagron schedule, week 11 (or whenever you approach the flower flip) is a water-only week. This is not optional if you want a clean transition. Give plain pH-adjusted water and let the medium clear before switching nutrient products. This also doubles as a diagnostic: if plants look lush and healthy through the flush week, your feeding program was calibrated correctly.

The tools you actually need (and how to use them)

You do not need a lot of gear, but these three things are non-negotiable for dialing in Terra Grow dosage correctly. If you are also growing valerian, it will generally grow best when you match the soil, temperature, and watering it prefers valerian grow best. If you want the exact floranova grow dosage for your stage, use EC readings to translate the target into the right amount for your tap water Terra Grow dosage correctly.

• EC/TDS meter: Measures the total dissolved solids in your nutrient solution. EC (mS/cm) is what Plagron's schedule uses. If your meter reads in TDS (ppm), use the 500 scale (1 mS/cm = approximately 500 ppm on the 500 scale, or 700 ppm on the 700 scale; check which scale your meter uses). Calibrate with a known EC calibration solution every few weeks. Rinse the probe after each use.
• pH meter: More important than any dosage chart. Calibrate with a two-point calibration using pH 7.0 and pH 4.0 buffers before each grow, and recheck calibration weekly. Store the probe in storage solution (not distilled water, which destroys the sensing membrane). If your readings seem unstable, recalibrate before troubleshooting anything else. Look for a meter with automatic temperature compensation (ATC) so temperature shifts in your mixing water do not skew readings.
• Graduated syringe or pipette (1–10 mL range): A 5 mL or 10 mL syringe lets you measure small volumes of Terra Grow accurately. Pouring from the bottle cap introduces major dosing errors, especially at the 1–2 mL/L range needed in early weeks.

Calculator workflow for each feed

1. Decide your batch size (e.g., 10 litres for a 2-pot setup).
2. Look up your target EC for the current week from the schedule.
3. Measure your tap water EC. Subtract from target EC to get the nutrient EC you need to add.
4. Start with a conservative Terra Grow dose (e.g., 3 mL/L if you are in week 5), multiply by batch size (3 mL x 10 = 30 mL total), and add to water.
5. Measure EC of the mixed solution. Adjust Terra Grow dose up or down by 0.5 mL/L increments until you hit the target EC.
6. Adjust pH to target range (5.8–6.5 for soil; 5.5–6.2 for coco-style).
7. Re-check EC, write down the final dose and EC reading, and feed.
8. After feeding, check runoff EC and pH if in a drain-to-waste setup. Log the results. After 2–3 feeds with consistent results, you have your reliable dose locked in for that week.

Plagron also offers a Grow Schedule Calculator on their website that lets you input your grow style and get a week-by-week breakdown with EC targets, which is a useful cross-reference against the manual approach above. It is worth running through it once to sanity-check your schedule, especially if you are running a longer veg period than the standard 10-week chart assumes. Compared to other nutrient lines covered on this site, such as FloraNova Grow, Terra Grow uses a single-bottle simplicity rather than a two-part system, which makes it easier to dial in but also means you have less flexibility to adjust individual nutrient ratios independently. For most home soil growers, that trade-off leans clearly in Terra Grow's favor.