Nutrient ranges are designed to look complicated: six bottles, a feeding chart with forty cells, and part numbers instead of names. Underneath it's simple. Plants need about a dozen elements, three of them in quantity, and the whole job is delivering them at the right strength and the right pH without letting salts pile up. Here's how, from reading a label to a feeding routine that works.
Reading a label: N-P-K
The three numbers on every feed — say 3-1-2 — are the percentages by weight of nitrogen (N), phosphorus (P) and potassium (K). Roughly:
- Nitrogen builds leaves and stems. Growth-stage food.
- Phosphorus builds roots and drives flowering and fruiting.
- Potassium runs everything — water movement, sugar transport, disease resistance — and is used heavily in flower.
That's why a veg formula is nitrogen-heavy (something like 3-1-2) and a bloom formula leans to P and K (1-3-2 or so). The rest of what a plant needs — calcium, magnesium, sulfur, and the micronutrients iron, manganese, zinc, boron, copper, molybdenum — is in any decent base feed, listed lower on the label in smaller numbers.
You do not need six bottles. A base veg, a base bloom, and cal-mag cover a first grow completely. The rest of a range (boosters, enzymes, "finishers") is refinement you can add later if you find a reason to.
Organic or mineral?
| Organic (amended soil, teas, meals) | Mineral / synthetic (salt-based liquids) | |
|---|---|---|
| How it feeds | Soil life breaks it down and releases it slowly | Directly available to the roots at once |
| Precision | Low — hard to over- or under-do quickly | High — you set the exact strength |
| Forgiveness | High; buffers mistakes | Low; mistakes show in days |
| Best medium | Soil | Coco, hydro, inert mixes |
| Measurement | Not really needed | pH and EC meters essential |
| Speed | Slower growth | Faster growth |
A good organic potting soil with the plant just watered is the easiest possible first grow. Mineral feeds in coco give more control and faster results once you're measuring. Neither is "better"; they're different amounts of involvement.
The two numbers: pH and EC
pH decides whether roots can take nutrients up. Get it wrong and the best feed in the world is locked out — the plant shows deficiencies with a full pot. Targets:
- Soil: 6.0–6.8
- Coco and hydro: 5.5–6.3, aiming at 5.8–6.0
Test the water after adding nutrients (they shift it), adjust with pH up or down, then test the runoff too. Runoff drifting away from the input tells you the medium is going out of range.
EC (electrical conductivity) is how much nutrient is in the water — its strength. PPM meters read the same thing on a different scale; know which scale yours uses (500 or 700), because charts differ. Typical ranges, in EC, including whatever's already in your tap water:
| Stage | EC (mS/cm) | PPM (500 scale) |
|---|---|---|
| Seedlings, cuttings | 0.4–0.8 | 200–400 |
| Early veg | 0.8–1.2 | 400–600 |
| Late veg | 1.2–1.6 | 600–800 |
| Flowering | 1.4–2.0 | 700–1000 |
| Late flower | 1.2–1.6, tapering | 600–800 |
These are starting points. Fast, heavy feeders take the top of a range; small plants and slow growers the bottom. The plant, not the chart, has the final say.
The dosing rule
Start at a quarter of the label dose. Every manufacturer's chart assumes ideal conditions and a plant at full tilt. Move up by a quarter each week only if the plant is pale and growing well with no burnt tips. Most plants end up happy at half to three-quarters of the label. Overfeeding shows as dark glossy leaves and crispy tips within days; underfeeding shows as slow pale growth over weeks and is trivially fixed. Err under.
A feeding routine
In soil: water plain for the first two or three weeks — a good potting mix has food in it. Then feed every second or third watering, plain water in between, at 10–20% runoff. Soil holds nutrients, so you're topping up, not supplying everything.
In coco: feed every watering, from the first week, because coco holds no nutrients of its own. Always with cal-mag — coco binds calcium and magnesium and starves the plant of them otherwise. Water to 10–20% runoff every time to keep salts from accumulating, and never let coco dry out completely.
Watering to runoff is the habit that prevents most problems. It flushes the salts from the last feed out of the bottom so they don't build up, and the runoff is your diagnostic: if its EC climbs well above what went in, salts are accumulating and it's time to flush with plain pH'd water.
Water quality
Tap water is fine for most people. Let it sit an hour to gas off chlorine (chloramine won't gas off, but at tap levels it's harmless). Tap water's own EC — typically 0.2–0.5 — counts toward your total, so a reading of 0.3 before you add anything is normal.
Very hard water (over ~0.6 EC) or RO water changes the picture: hard water may need less cal-mag, RO needs it every time because it has nothing in it. Don't add cal-mag and have hard water without checking; too much calcium locks out magnesium and potassium.
Root temperature
Nutrient uptake — phosphorus especially — falls off sharply when the root zone is below about 60 °F. Plants on a cold garage floor show phosphorus deficiency with a full pot. Keep pots off concrete, and if the room is cold, a seedling heat mat under the pots does more than any bottle.
Flushing
Two kinds. The salt flush — when runoff EC is far above input, or after nutrient burn — is uncontroversial: water with plain pH'd water to heavy runoff, let the pot dry, and resume feeding lower. The pre-harvest flush — plain water for the last week or two — is widely practised and widely debated; with mineral feeds it's cheap insurance and does no harm, so it's reasonable to do without expecting miracles from it.
The mistakes
- Following the label dose. Quarter strength first, always.
- Not measuring pH. The single cause of most "mystery" deficiencies.
- Feeding a wet pot. Water only when the pot is light; feeding a waterlogged plant adds salt to roots that can't breathe.
- Skipping runoff. Salts accumulate silently for weeks and then everything goes wrong at once.
- Fixing three things at a time. Change one variable, wait a week, judge the new growth.
- Coco without cal-mag. Calcium and magnesium deficiencies are almost guaranteed.
When a plant does go wrong, Diagnosing nutrient deficiencies walks through reading the leaves.
Shopping list
A base veg feed, a base bloom feed, cal-mag, pH up and down, a pH pen, an EC meter, and a jug for mixing. That's a complete nutrient setup for a first grow. Everything else in the range can wait until you have a reason for it.
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