Everything we know about feeding plants, in one place
We've manufactured fertilizer in Madera, California since 1989, and these guides come out of that work — real label rates, real formulation reasoning, and the honest answer when a product isn't the right fit. Start with your crop, jump straight to a tool, or work through the fundamentals.
Free tools
Three things you can't get from a search result: exact rates for your setup, a diagnosis based on your actual conditions, and a starting point when you don't know what you need.
Fertilizer Calculator
Deficiency Identifier
Fertilizer Finder Quiz
Feeding guides by crop
What each crop actually needs, when it needs it, and the rates to apply — for soil, containers, and hydroponics.
Tomatoes
Peppers
Lettuce & Leafy Greens
Strawberries
Herbs
Cucumbers & Vines
Roses & Flowers
Citrus & Fruit Trees
Avocado
Azaleas & Acid Lovers
Houseplants & Indoor
Lawns
Palms & Tropicals
How plant nutrients work
Fourteen mineral nutrients, three of them on every label. What each one does inside the plant, how a shortage shows up, and which fertilizer supplies it — the reading underneath both the crop guides and the deficiency identifier. Diagnosing rather than learning? Go straight to the identifier.
Primary macronutrients — the N-P-K on the label
Proteins, chlorophyll, nucleic acids — the growth engine, and the nutrient most often short in garden soil. Shortage yellows the oldest leaves first and works upward. Ammonium, nitrate and urea move and act differently in soil, so the source matters as much as the number. Shop nitrogen →
Energy transfer (ATP), cell division, root establishment and reproductive growth; demand peaks at germination and transplanting. Purple-tinged older leaves are the classic sign — in cold soil, usually an uptake problem rather than a true shortage. On the label it's available phosphate (P₂O₅). Shop phosphorus →
Not a building block — an ionic regulator: stomata and water balance, sugar transport into fruit, and the activity of dozens of enzymes. Marginal scorch on older leaves first. The "quality nutrient" for fruit size, firmness and shelf life. On the label it's soluble potash (K₂O). Shop potassium →
Secondary macronutrients
Cell walls (calcium pectate) and the growing tips of roots and shoots. Immobile, so new growth suffers first — tip burn, distorted young leaves, blossom end rot — and most cases are a delivery problem (uneven water, high transpiration) before they're a soil problem. Shop calcium & magnesium →
The atom at the center of every chlorophyll molecule, and required wherever the plant spends energy (ATP). Mobile — interveinal chlorosis on older leaves first — and most common on sandy, leached, or potassium-heavy soils. Shop calcium & magnesium →
Two amino acids (cysteine, methionine), so every protein and enzyme; also chlorophyll formation and the flavor compounds in onions, garlic and brassicas. Taken up as sulfate. Yellowing on the newer leaves — nitrogen deficiency's look-alike, from the other end of the plant. Shop elemental sulfur →
Read the three together: Secondary Nutrients in Plants — the Ca, Mg, S guide.
Micronutrients
Needed in tiny amounts, and mostly a pH story: iron, zinc, manganese and copper drop out of reach as soil pH climbs past roughly 6.5, molybdenum does the opposite, and boron leaches. Most are immobile, so trouble shows on new growth first. This is where sulfate vs. chelated matters more than anywhere else.
Not part of chlorophyll, but required to make it — plus the electron-transport chains of photosynthesis and respiration, and nitrate reduction. Interveinal chlorosis on the newest leaves. Above about pH 6.5–7.0 it's usually lockout, not absence, which is why chelate choice (DTPA vs. EDTA vs. ferrous sulfate) is the whole decision. Shop iron & micronutrients →
Auxin production (so internode length), protein synthesis and enzyme activation. Small leaves, short internodes and rosetting on new growth, with interveinal chlorosis. Locked up by high pH and by heavy phosphorus — pecans, citrus and corn show it first. Shop zinc & micronutrients →
Photosynthesis (the water-splitting step of Photosystem II), enzyme activation and nitrogen metabolism. Interveinal chlorosis on new-to-middle-aged leaves rather than only the newest — the practical tell against iron — and "frizzle top" on palms. Shows up above pH 6.5, on organic soils, and in cool wet springs. Shop manganese & micronutrients →
Lignin and cell-wall strength, photosynthetic electron transport, and several enzyme systems. Wilting, pale twisted young leaves and dieback of shoot tips; most likely on peat and muck soils and at high pH. The margin to toxicity is narrow — it's the micronutrient to be stingiest with. Shop copper & micronutrients →
Cell-wall structure, cell division at growing points, pollen-tube growth and fruit set, and moving sugars. Death of the growing point, hollow stems, corky or cracked fruit, poor set — on sandy leached soils and at high pH. Deficient and toxic are only a few ppm apart, so it's a measure-first nutrient. Shop boric acid →
Required by the enzymes that reduce nitrate to usable nitrogen and, in legume nodules, fix it from the air. Pale, cupped or strap-like leaves — cauliflower "whiptail" — and nitrogen-deficiency symptoms on plants with plenty of nitrate. The one micronutrient that becomes less available as pH drops; liming an acid soil is usually the fix. Shop Micro Green (carries Mo) →
The full set in one read: Essential Micronutrients: Boost Your Garden Soil for Healthier Plants. Chlorine and nickel round out the fourteen — both essential, both rarely short in practice; the Major vs. Trace guide covers them.
Fertilizer fundamentals
Which product for which job — the buying guides, the sulfate-vs-chelate question, and how to build fertility before you plant.
Best Fertilizers for a Vegetable Garden
Organic and water-soluble options for every vegetable, from root crops to fruiting plants, with rates and timing across the season.
Best Organic Fertilizer for Vegetables
Which organic amendment for which job — fast nitrogen, season-long nitrogen, phosphorus at transplant, and potassium with stress support.
Seven options compared, from fast-acting urea to slow-release feather meal, with a decision guide for garden, lawn, and hydroponics.
Best Water-Soluble Fertilizers for Every Crop
Matching formula to crop and growth stage, and why solubility matters for hydroponics, fertigation, and foliar feeding.
Sulfate vs. Chelated Micronutrients
Why chelates cost more, when they're worth it, and why sulfate forms fail above pH 7.0 — the single most useful thing to understand about micronutrients.
The Organic Gardener's Guide to Soil Preparation
Building fertility before you plant — amendments, timing, and how to read a soil test.
Something's wrong with my plant
Why Are My Plant's Leaves Turning Yellow?
Nine causes, how to tell them apart, and which ones fertilizer will and won't fix.
Fertilizer Toxicity vs. Nutrient Deficiency
Too much and too little produce symptoms that look alike. How to tell which one you're looking at before you feed — because guessing wrong doubles the damage.
Blossom end rot on tomatoes or peppers
Usually a calcium transport failure caused by uneven watering, not a soil calcium shortage. Fix the moisture consistency first — the identifier explains why.
Yellow leaves with green veins
Interveinal chlorosis. On new growth it's iron (usually pH lockout above 6.5); on old growth it's magnesium. Compare the reference photos →
Brown crispy tips with white crust on the soil
Salt buildup, not hunger — and feeding makes it worse. Most common in containers and houseplants. How to flush it out →
Not sure how much to apply
The calculator carries our actual label rates across every application method — no more guessing at "a scoop per gallon."
Ready to shop
Browse all fertilizers, or start from what you're growing or the nutrient you need.
Shop by crop: Tomatoes & Vegetables · Lettuce & Leafy Greens · Peppers & Herbs · Strawberries & Berries · Cucumbers & Vines · Roses & Flowers · Azaleas & Acid Lovers · Citrus & Fruit Trees · Palms & Tropicals · Houseplants & Indoor · Lawns
Questions about your specific situation? Email questions@greenwaybiotech.com or call (562) 351-5168, Monday–Friday 7AM–5PM PST — you'll reach people who make the products.
