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Epsom Salt USP grade (magnesium sulfate), 25 lb bag

Epsom Salt for Plants (Magnesium Sulfate) for Gardens, Fruit & Hydroponics

Regular Price: $ 21.99

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Price per lb by size: larger sizes save up to 75%

Size	Price	Per lb	Per lb vs 2 Pounds
2 Pounds	$ 21.99	$ 7.33	–
5 Pounds	$ 24.99	$ 5.00	32% less
10 Pounds	$ 33.99	$ 3.40	54% less
25 Pounds	$ 51.99	$ 2.08	72% less
2 X 25 Pounds	$ 89.99	$ 1.80	75% less

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The 2 x 25 lb size ships as two separate 25 lb bags.

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Magnesium and sulfur for plants · MgSO₄·7H₂O

About Epsom Salt for Plants

Epsom salt corrects a magnesium shortage; plants that already have enough gain nothing from it. University guides use it where a soil test reads low, where a leaf test or yellowing between the veins of older leaves shows a deficiency, and in hydroponic recipes. Every amount below is a weight, with its crop and source beside it.

9.86% Mg Magnesium, by the formula of the pure compound. Each pound holds about 44.7 g
13.0% S Sulfur, as sulfate. No nitrogen, phosphate or potash
23 g per gallon The starting strength of a vegetable leaf spray (University of Delaware). The calculator works out sprays, plants, beds, lawns and solutions

Product facts & composition

Composition and specifications, Greenway Biotech Epsom Salt for Plants
Specification	Detail
Ingredient	Magnesium sulfate heptahydrate (MgSO₄·7H₂O), CAS 10034-99-8
Magnesium (Mg)	9.86% by weight in the pure compound (24.305 ÷ 246.47), which is 16.4% expressed as magnesium oxide (MgO). One pound holds about 44.7 g of magnesium
Sulfur (S)	13.0% by weight, as sulfate. One pound holds about 59 g of sulfur
Nitrogen, phosphate (P₂O₅), potash (K₂O), calcium	None
Grade	USP-grade raw material, per the producer’s certificate of analysis, repackaged without changes
Solubility	Very soluble in water, which helps when making solutions and injecting them (University of California Cooperative Extension)
In solution	1 g per liter adds 98.6 ppm magnesium and 130 ppm sulfur; 1 g per US gallon adds 26.1 ppm magnesium and 34.4 ppm sulfur
Package sizes	1, 3, 5, 10, 20 and 25 lb, and 50 lb as two 25 lb bags

The magnesium and sulfur figures are calculated from the chemical formula, and every amount on this page uses them. Soil reports sometimes give magnesium as magnesium oxide (MgO); multiply an MgO figure by 0.603 to convert it to magnesium. Weigh the product: this page gives no spoon or cup conversions, because the weight of a spoonful depends on the crystal size.

Best uses & benefits

Choose it when a test or the plant itself shows magnesium is short, and you want magnesium without nitrogen, potassium or calcium, or without raising soil pH.

Vegetables showing magnesium deficiency

The University of Delaware calls it a common problem with tomatoes and notes that all vegetables are susceptible; it corrects it with a magnesium sulfate leaf spray alongside a soil application. South Dakota State applies it per plant or as a drench in high tunnels. See the rates.

Soil that tests low in magnesium but needs no lime

The University of Connecticut’s soil lab recommends Epsom salts where calcium and soil pH are adequate but magnesium is low. Where lime is also needed, dolomitic lime supplies the magnesium instead.

Apples, grapes and berries with a confirmed shortage

University guides give magnesium sulfate sprays for apples and grapes and soil or injected rates for blueberries, muscadines and strawberries, each tied to a leaf or soil analysis.

Hydroponic and greenhouse solutions

Both single-salt recipes in Cornell’s hydroponic guide take their magnesium from magnesium sulfate, and UMass Extension adds it monthly where the fertilizer in use has no magnesium.

Where it is a poor fit

Plants that are not short of magnesium. Washington State University’s Linda Chalker-Scott finds the science behind Epsom salt applies to crop production where magnesium is known to be deficient, and that magnesium plants do not use accumulates in the topsoil, while under leaching conditions it adds minerals to the water passing through. The University of Minnesota recommends no magnesium for fruit and vegetable crops on soils testing above 150 ppm.
Acid soil that also needs lime. The University of Minnesota calls dolomitic lime the most cost-effective way to apply magnesium, and the University of Georgia uses it on apples and muscadines when soil pH is low. See Dolomite.
Blossom-end rot. It is a calcium disorder, and Epsom salt contains no calcium. North Dakota State notes that magnesium and calcium compete for uptake, so adding Epsom salt to the soil may make it worse.
Balancing a calcium-to-magnesium ratio. The University of Minnesota reports that the need for an ideal ratio has never been verified by research in the Corn Belt, and that adjusting the ratio with Epsom salts has not been shown to significantly benefit plant growth.
Palms. University of Florida guidance prefers kieserite, a less soluble form of magnesium sulfate, as a controlled-release magnesium source for palms on neutral to alkaline soils. This page gives no palm rate.
A calcium concentrate. Calcium and sulfate form insoluble gypsum in concentrated stock solutions, so it never goes in the calcium nitrate tank.

Application rates & directions

Find your situation, then weigh the amount; a kitchen scale that reads to 1 g covers most uses. Every rate comes from the university source named beside it, scoped to the crop and conditions it was written for. Start at the low end of any range, spray a few plants first, and use a soil or leaf test where you can. The calculator does the arithmetic.

Confirm the need first. Magnesium moves within the plant, so a shortage shows first in the oldest leaves as yellowing between the veins while the veins stay green (University of Minnesota; University of Delaware). The University of Minnesota notes that diseases, herbicide injury and environmental stress cause similar damage, and UMass Extension notes that iron or manganese toxicity from low pH in container mixes can look like advanced magnesium deficiency.

Leaf sprays

Epsom Salt for Plants leaf sprays by crop, as published and converted to grams per US gallon of spray
Crop	Rate as published	Per gallon of spray	When and how	Source
Tomatoes, melons, beans and other vegetables showing deficiency	0.5–2 lb of magnesium per acre as magnesium sulfate, sprayed in 100 gal of water per acre (20 lb of magnesium sulfate in 100 gal is the example given)	23–91 g (5–20 lb per 100 gal)	When the deficiency appears, alone rather than with pesticides, at dusk or early evening, with moderate temperatures and low wind. Pair it with a soil application	University of Delaware
Apples, where leaf analysis shows a need	15 lb per 100 gal	68 g	Petal fall, first cover and second cover sprays. Avoid slow-drying conditions and temperatures above 80 °F, and do not tank-mix with urea on young trees	University of Georgia; UConn Extension
Grapes	4 lb per 100 gal	18.1 g	One or more sprays in spring, at 150–250 gal per acre. Higher concentrations can burn leaves	University of California Cooperative Extension

The University of Delaware notes that foliar fertilizers are salts that damage leaves at high rates, that solutions of 0.5–2% are generally recommended, and that some vegetables are more sensitive than others; 23 g per gallon is 0.6%, and 91 g is 2.4%. Leaf sprays work quickly but briefly: the University of Georgia calls them temporary treatments, and UC’s grape guide notes they must be repeated each year, so correct the soil as well.

Plants and beds already showing deficiency, without a soil test

Epsom Salt for Plants for vegetables already showing magnesium deficiency, by method
Method	Rate as published	This product	Source
Side dressing, per plant	About ½ oz per plant, for high tunnel crops showing symptoms	14 g per plant	South Dakota State University Extension
Drench	1 to 2 lb dissolved in 100 gal of water, for high tunnel crops showing symptoms	4.5–9.1 g per gallon	South Dakota State University Extension
Broadcast on a bed, watered in	15–25 lb of magnesium per acre	158–264 g per 100 sq ft	University of Delaware
Side dressing along a row or bed	15–20 lb of magnesium per acre	158–211 g per 100 sq ft	University of Delaware

South Dakota State applies Epsom salt only when plants show symptoms, and says not to mix it with another water-soluble fertilizer in the drench. The University of Georgia’s greenhouse tomato guide gives 5 lb per 1,000 sq ft (227 g per 100 sq ft) on deficient plants, inside Delaware’s range.

Garden beds and fields by soil test

The University of Minnesota sets magnesium for fruit and vegetable crops by the soil test’s magnesium level in parts per million (ppm). Spread it evenly and mix it into the soil before planting.

Epsom Salt for Plants for fruit and vegetable crops by soil-test magnesium, from University of Minnesota rates of 100, 50 and 0 lb of magnesium per acre broadcast
Soil-test magnesium	Per 100 sq ft	Per 1,000 sq ft	Per acre, broadcast	Per acre, banded
0–50 ppm (low)	2.33 lb (1,056 g)	23.3 lb	1,014 lb	203 lb
51–150 ppm (medium)	1.16 lb (528 g)	11.6 lb	507 lb	101 lb
Over 150 ppm (high)	None	None	None	None

In Minnesota, magnesium deficiency has been seen only on very acid soils, below about pH 5.5, mostly sandy ones; there, dolomitic lime raises the pH and supplies magnesium together. The University of Georgia applies magnesium sulfate when soil pH is 6 or higher and uses dolomitic lime below that. These are Minnesota calibrations; if your state lab gives its own magnesium recommendation, use it with the soil test report formula below.

Containers, greenhouses and high tunnels

Epsom Salt for Plants dissolved in water for container, greenhouse and high tunnel crops
Purpose	Rate as published	Per gallon of water	Source
Correct a deficiency	1–2 lb per 100 gal as a drench (South Dakota State); 2 lb per 100 gal (UMass)	4.5–9.1 g	South Dakota State University Extension; UMass Extension, on greenhouse tomatoes
Prevent a deficiency when the fertilizer in use has no magnesium	1 lb per 100 gal, monthly	4.5 g	UMass Extension, on greenhouse tomatoes

1 lb per 100 gal adds about 118 ppm magnesium to the water. Check whether your fertilizer already contains magnesium before adding more.

Lawns

The University of Minnesota recommends 1 lb of magnesium per 1,000 sq ft only where soil-test magnesium is 0–50 ppm, and none above 50 ppm. That is 10.1 lb (4,600 g) of this product per 1,000 sq ft, or 1.01 lb (460 g) per 100 sq ft. Minnesota gives its secondary-nutrient recommendations for intensively grown turf, such as golf courses and sod farms, and notes that magnesium deficiency occurs on acid, sandy soils or where high rates of potassium fertilizer induce it. Without a soil test, this page gives no lawn amount.

Fruit trees, vines and berries (commercial, leaf-test based)

Magnesium sulfate rates for fruit crops from leaf or soil analysis, with the weight of this product that supplies them
Crop and condition	Rate as published	This product	Source
Apples, soil pH 6 or higher and magnesium low	20 lb of magnesium per acre as Epsom salts, to the soil; below pH 6, dolomitic lime from a soil test	203 lb per acre (4.66 lb per 1,000 sq ft)	University of Georgia
Blueberries in soil, leaf magnesium below 0.12%	15–25 lb of magnesium per acre as magnesium sulfate or another soluble form	152–254 lb per acre (3.49–5.82 lb per 1,000 sq ft)	University of Georgia
Muscadine grapes, leaf magnesium below 0.15% and soil pH 5.5–6.0	25 lb of magnesium per acre as Epsom salt or potassium-magnesium sulfate; below pH 5.5, dolomitic lime	254 lb per acre (5.82 lb per 1,000 sq ft)	University of Georgia
Strawberries, leaf magnesium below 0.25%	Inject 20 lb of magnesium sulfate per acre per week; retest in 3 weeks	20 lb per acre per week	University of Georgia
Drip-irrigated grapevines, severe deficiency	0.5–1 lb of magnesium sulfate per vine, which the authors suggest from comparative research; 2–4 lb per vine with furrow irrigation	0.5–1 lb (227–454 g) per vine	University of California Cooperative Extension

These are commercial guidelines tied to a leaf test. The University of Georgia corrects peach orchards with dolomitic lime instead.

Hydroponic and fertigation nutrient solutions

Formula. Grams of product = (magnesium target − magnesium already in your water, in ppm) × liters of final solution ÷ 98.6. Multiply US gallons by 3.785 for liters. Each ppm of magnesium from this product also adds 1.32 ppm of sulfur.

Weight of Epsom Salt for Plants in the two single-salt recipes in Cornell’s hydroponic guide, starting from water with no magnesium
Recipe	Magnesium it supplies	Per 100 US gal	Per 1,000 L	Sulfur it adds
Modified Sonneveld solution, lettuce and leafy greens	24 ppm	93.1 g	246 g	32 ppm
University of Arizona CEAC recipe, tomatoes, cucumbers and peppers	48 ppm	184.3 g	487 g	63 ppm
Each 10 ppm for your own recipe	10 ppm	38.4 g	101 g	13 ppm

Both recipes dissolve magnesium sulfate in a different stock tank from the calcium nitrate; the Arizona recipe puts it with monopotassium phosphate and potassium sulfate. Cornell’s guide also gives tomato magnesium targets of 65, 60 and 48 ppm as the crop matures. Subtract any magnesium already in your water.

Keep it out of calcium concentrates. Cornell notes that calcium can combine with phosphates and sulfates to form insoluble precipitates, so recipes keep calcium nitrate in one stock tank and the sulfates and phosphates in the other; the two meet only in the diluted final solution. UC Agriculture and Natural Resources reports that a sulfate fertilizer injected into water with more than 2 to 3 meq/L calcium (about 40 to 60 ppm) may precipitate gypsum, so jar-test first: mix it into your water at the line concentration, let it stand overnight, and look for cloudiness or sediment.

From a soil test report

Formula. Pounds of this product = pounds of magnesium (Mg) your report calls for ÷ 0.0986. If the report gives magnesium oxide (MgO), multiply by 0.603 first. If it gives pounds per acre, divide by 43.56 for pounds per 1,000 sq ft. For example, 20 lb of magnesium per acre is 203 lb of this product per acre, or 4.66 lb per 1,000 sq ft, adding 26.4 lb of sulfur per acre.

Your package label

This page gives university rates matched to your crop, test or recipe, and does not restate the directions printed on your package. If the directions on your package differ from this page, email questions@greenwaybiotech.com before applying.

Uses with no amount on this page

This page gives no amount for roses, houseplants, citrus, palms, trees and shrubs without a leaf test, seed starting, or a lawn without a soil test, because none of the sources read gives a weighed rate for them. For any of these, email questions@greenwaybiotech.com with your plants, how they are grown, and any soil or leaf test.

How to use Epsom Salt for Plants

Confirm magnesium is short. Look for yellowing between the veins of the oldest leaves, and use a soil or leaf test where you can. If the soil test also calls for lime, use dolomitic lime instead.
Find the amount and weigh it. Use the tables or the calculator. A scale reading to 1 g covers sprays, plants and beds; one reading to 0.1 g helps with small nutrient batches.
Dissolve or spread it. For a spray, drench or solution, stir it into water until it dissolves. For soil, spread it evenly and water it in, or mix it into the bed before planting.
Spray with care. Spray a few plants first, in the cool of dusk or early evening, and keep it out of calcium concentrates.
Retest before repeating. Repeat only as the source for your crop directs, and retest the soil or leaves before adding more.

Calculator & choosing a size

Formulas. Sprays: grams = grams per gallon for your crop × gallons of spray. Plants: 14 g per plant. Drenches: 4.5 to 9.1 g per gallon of water. Beds and fields: pounds = square feet ÷ 43,560 × pounds of magnesium per acre ÷ 0.0986. Lawns: 10.1 lb per 1,000 sq ft where soil magnesium tests 0–50 ppm. Solutions: grams = (ppm magnesium target − ppm in your water) × liters ÷ 98.6. Multiply pounds by 453.6 for grams.

Worked examples.

Six tomato plants showing deficiency, side-dressed at 14 g each: 85 g; a 1 lb bag covers it.
A 1-gallon vegetable spray at the starting strength: 23 g; a 1 lb bag covers it. The top of the range, 91 g, would also fit in a 1 lb bag.
25 gallons of apple spray at 15 lb per 100 gallons: 3.75 lb (1,701 g); a 5 lb bag covers one spray.
A 200 sq ft vegetable bed testing 40 ppm magnesium: 2 × 1,056 g = 2,112 g (4.66 lb); a 5 lb bag covers it.
A 100-gallon hydroponic batch at the Arizona recipe’s 48 ppm, from water with no magnesium: 184 g; a 1 lb bag covers it.

What each bag covers: plants side-dressed at 14 g each, vegetable spray at the 23 g per gallon starting strength, container drench at 1 lb per 100 gallons, garden beds testing 51–150 ppm magnesium (528 g per 100 sq ft), or hydroponic solution at 48 ppm magnesium (184.3 g per 100 gallons)
Bag size	Plants, side-dressed	Vegetable spray	Container drench	Garden bed	Solution at 48 ppm
1 lb (454 g)	32 plants	19 gal	100 gal	85 sq ft	246 gal
3 lb (1,361 g)	96 plants	59 gal	300 gal	257 sq ft	738 gal
5 lb (2,268 g)	160 plants	98 gal	500 gal	429 sq ft	1,230 gal
10 lb (4,536 g)	320 plants	197 gal	1,000 gal	859 sq ft	2,461 gal
20 lb (9,072 g)	640 plants	394 gal	2,000 gal	1,718 sq ft	4,922 gal
25 lb (11,340 g)	800 plants	493 gal	2,500 gal	2,147 sq ft	6,152 gal
50 lb as 2 × 25 lb (22,680 g)	1,600 plants	986 gal	5,000 gal	4,295 sq ft	12,305 gal

The calculator below asks what you are treating and then, depending on your answer, the crop and spray volume, the number of plants, the water volume, the area and your soil test, or your solution volume and magnesium target. It applies the rate from the tables above, starting at the low end of any range, states the magnesium and sulfur supplied, and recommends the smallest bag that covers one spray, application or batch, plus a lower-price combination of bags when one exists. Prices, tax and shipping are confirmed at checkout, and availability is confirmed when you add to cart.

The calculator needs JavaScript. If it does not appear, use the rate tables and formulas above to choose a size.

How magnesium sulfate works

In water, Epsom salt dissolves into magnesium (Mg²⁺) and sulfate (SO₄²⁻). Magnesium is part of the chlorophyll molecule, so a shortage reduces chlorophyll and the leaf yellows (Washington State University). It moves within the plant, so the plant draws it from older leaves for new growth, and deficiency shows first low on the plant (University of Minnesota). Sulfate is the form of sulfur that plant roots absorb (University of Minnesota).

Shortages are most common on light, sandy or acid soils (Washington State University; University of Minnesota), and the University of Delaware finds them most often on sandy soils below pH 5.4. Large amounts of potassium can induce magnesium deficiency where soil magnesium is low to moderate (University of Delaware), and South Dakota State sees deficiency in high tunnels mid-season on plants carrying a heavy fruit load. Rutgers notes that calcium, potassium and magnesium compete for uptake, so the right amount of each comes from soil and tissue testing.

More is not better. Washington State University reports that magnesium unused by plants accumulates in the topsoil and that, in one pasture study, 49% of applied Epsom salts was lost to leaching. This describes magnesium and sulfate nutrition in general; it is not a trial of this finished product.

Compare your options

Match the product to what your test shows. Analyses for the other products are as shown on their pages.

Epsom Salt for Plants compared with other Greenway magnesium sources
Option	Supplies	Choose it when	Limitation
Epsom Salt for Plants, this product	9.86% magnesium and 13.0% sulfur; nothing else	A test or symptoms show magnesium is short, and you want no nitrogen, potassium or calcium with it	Not a liming material; keep it out of calcium concentrates
Magnesium Nitrate 11-0-0	9.6% magnesium and 11% nitrate nitrogen	The crop can use the nitrogen, or the magnesium must share the calcium nitrate tank	Adds about 1.15 lb of nitrogen with every pound of magnesium
Dolomite	Calcium and magnesium, as limestone	A soil test calls for lime and magnesium is also low	Raises soil pH; slow; not for sprays or solutions
Sulfate of Potash Magnesia	Potash with magnesium and sulfur, from a mined mineral	The soil needs potassium as well as magnesium	Soil use only; adds potassium whether or not you need it
Cal-Mag Plus 2-0-0 Concentrate	Calcium, magnesium, chelated iron and nitrate nitrogen	A hydroponic reservoir needs calcium and magnesium together	Much less magnesium per pound; follow the directions on its page

Handling, storage & limitations

Handling. Avoid breathing dust when pouring, keep it out of your eyes, and wash your hands after handling. Sold for plant use; keep it out of reach of children and pets.
Sprays. Spray a few plants first. Spray at dusk or in the early evening with moderate temperatures and little wind (University of Delaware); on apples, avoid slow-drying conditions and temperatures above 80 °F (UConn Extension).
Use limits. Apply only where a test or symptoms show magnesium is short, weigh every application, and retest before repeating. It adds no nitrogen, phosphate, potash or calcium and is not a complete fertilizer. Keep it out of calcium concentrates.
Environment. Magnesium that plants do not use accumulates in the topsoil, and under leaching conditions it adds minerals to the water passing through (Washington State University). Sweep up spills and keep the product and runoff out of storm drains and waterways.
Storage. Keep the bag closed, dry and out of reach of children and pets.
First aid. Eyes: rinse with clean water for several minutes and get medical advice if irritation continues. Skin: wash with water. Swallowed: call Poison Control at 1-800-222-1222 or a doctor for advice.

Frequently asked questions

How much Epsom salt do I mix per gallon for a leaf spray?

It depends on the crop. For vegetables showing magnesium deficiency, University of Delaware rates work out to 23–91 g of this product per US gallon; start at 23 g. For apples where a leaf analysis shows a need, it is 68 g per gallon (15 lb per 100 gallons), and for grapes 18.1 g (4 lb per 100 gallons). Weigh it on a scale, spray a few plants first, and spray in the cool of dusk or early evening.

Will Epsom salt fix yellow leaves?

Only when magnesium is the cause. Magnesium deficiency shows first on the oldest leaves, as yellowing between the veins while the veins stay green. The University of Minnesota notes that diseases, herbicide injury and environmental stress cause similar damage, and UMass Extension notes that low pH in container mixes can cause look-alike symptoms. A soil or leaf test confirms it.

Does Epsom salt prevent blossom-end rot?

No. Blossom-end rot is a calcium disorder, and Epsom salt contains no calcium. North Dakota State University notes that magnesium and calcium compete for uptake, so adding Epsom salt to the soil may lead to more rot, not less. Because calcium moves into the plant with water, it recommends regular watering that keeps the soil neither waterlogged nor dry, with mulch to hold moisture steady.

Should I add Epsom salt to every tomato planting hole?

Not unless magnesium is short. Washington State University finds the science behind Epsom salt applies where magnesium is known to be deficient, and that magnesium plants do not use accumulates in the topsoil. For tomato plants already showing deficiency, South Dakota State side-dresses about ½ oz (14 g) per plant.

How much do I put on my lawn?

Go by a soil test. The University of Minnesota recommends 1 lb of magnesium per 1,000 sq ft, which is 10.1 lb (4,600 g) of this product, only where soil magnesium tests 0–50 ppm, and none above 50 ppm. Minnesota gives these recommendations for intensively grown turf, such as golf courses and sod farms. Without a soil test, this page gives no lawn amount.

How much do I add to a hydroponic reservoir?

Grams of product = (magnesium target − magnesium already in your water, in ppm) × liters of final solution ÷ 98.6. Cornell’s hydroponic guide uses 93.1 g per 100 US gallons (24 ppm magnesium) in a lettuce recipe and 184.3 g per 100 gallons (48 ppm) in the University of Arizona recipe for tomatoes, cucumbers and peppers. Each ppm of magnesium also adds 1.32 ppm of sulfur.

Can I mix it with calcium nitrate?

Not in the same concentrate. Cornell notes that calcium can combine with sulfates and phosphates to form insoluble precipitates, so recipes keep calcium nitrate in one stock tank and magnesium sulfate in the other, and the two meet only in the diluted final solution. If your water carries more than about 40 to 60 ppm calcium, jar-test before injecting.

Should I use Epsom salt or dolomitic lime?

Go by your soil test. If it calls for lime and magnesium is low, dolomitic lime raises the pH and supplies magnesium together; the University of Minnesota calls it the most cost-effective magnesium source. If pH and calcium are already adequate but magnesium is low, the University of Connecticut’s soil lab recommends Epsom salts.

Do I need to balance a calcium-to-magnesium ratio?

No. The University of Minnesota reports that the need for an ideal calcium-to-magnesium ratio has never been verified by research in the Corn Belt, and that adjusting the ratio with gypsum or Epsom salts has not been shown to significantly benefit plant growth. Go by the magnesium level on your soil test instead.

Is this the same Epsom salt as your bath listing?

It is the same magnesium sulfate heptahydrate, sold here with plant directions; the bath listing carries the bath and foot-soak directions. For bath use, see Epsom Salt USP Grade for bath and foot soaks.

Related guides & articles

Why Soil pH Plays a Bigger Role in Your Garden Than You Might Think: how pH controls nutrient availability, how to test it, and when dolomite lime, which adds magnesium, is the right way to raise it.

Articles give background. For this product, use the weighed rates on this page.

Product documents & sources

Product label: printed on every package. A PDF copy is not posted on this page yet. See Your package label under Application rates.
Safety Data Sheet: not posted on this page yet. For handling questions, email questions@greenwaybiotech.com.

Where the rates and statements on this page come from

The rates and agronomic statements on this page come from the university publications below, listed for growers, advisors and anyone who wants to check them; they explain plant nutrition in general and do not evaluate or endorse this product.

University of Minnesota Extension, Magnesium for Crop Production (Daniel E. Kaiser and Carl J. Rosen): soil-test magnesium classes and fruit and vegetable rates, dolomitic lime as the most cost-effective source, where deficiency occurs, symptoms in the oldest leaves, look-alike causes, and the calcium-to-magnesium ratio.
University of Minnesota Extension, Soil Test Interpretations and Fertilizer Management for Lawns, Turf, Gardens, and Landscape Plants (BU-01731, Rosen, Bierman, and Eliason, revised 2008; archived): turf magnesium by soil test (Table 18), where deficiency occurs, and adjusting calcium-to-magnesium ratios.
University of Minnesota Extension, Sulfur for Minnesota Soils (Kaiser and Vetsch): sulfate as the form of sulfur roots absorb.
Gordon Johnson, University of Delaware, Magnesium Deficiencies in Vegetables Revisited (Weekly Crop Update, May 10, 2019): symptoms, sandy acid soils and potassium, the magnesium sulfate spray, and broadcast and sidedress rates.
Gordon Johnson, University of Delaware, on foliar fertilizers in vegetable crops (Weekly Crop Update): foliar magnesium rates for tomatoes, melons and beans, 0.5–2% solutions, salt injury, and spray timing.
Geoffrey Njue, South Dakota State University Extension, Monitoring and Correcting Magnesium Deficiency in High Tunnels (updated September 26, 2024): side dressing per plant, drench rates, applying only when symptoms show, and causes of deficiency.
Geoffrey Njue and Angela Madeiras, UMass Extension, Greenhouse Update, May 1, 2026: correcting and preventing magnesium deficiency in greenhouse tomatoes, and low-pH look-alike symptoms.
University of Georgia, Plant Analysis Handbook for Georgia (C. Owen Plank and David E. Kissel): Apple, Greenhouse Tomato, Blueberry in soil, Muscadine, Strawberry, and Peach: magnesium corrections by leaf analysis and soil pH.
Mary Concklin, UConn Extension, Tree Fruit Foliar Nutrient Applications: apple Epsom salt sprays, their timing, and the cautions on heat, drying and urea.
Bill Peacock and Pete Christensen, University of California Tulare County Cooperative Extension, Magnesium Deficiency Becoming More Common (NG5-96): grape foliar and per-vine rates, leaf burn at higher concentrations, and the solubility of magnesium sulfate.
University of Connecticut Soil Nutrient Analysis Laboratory, Standard Nutrient Analysis: when Epsom salts are recommended.
Linda Chalker-Scott, Washington State University, Epsom Salts (MasterGardener, Spring 2007): when Epsom salt is justified, magnesium in chlorophyll, soils prone to deficiency, and accumulation and leaching.
Tom Kalb, North Dakota State University Extension, The Epsom Salt Myth (2016): Epsom salt, blossom-end rot and watering.
Michelle Infante-Casella, Rutgers Cooperative Extension, Magnesium Deficiency in Tomato and the Relationship with other Important Nutrients (June 8, 2023): competition among calcium, potassium and magnesium.
Timothy K. Broschat, UF/IFAS Extension, Magnesium Deficiency in Palms (EP266): kieserite as the preferred magnesium source for palms.
Neil S. Mattson and Cari Peters, A Recipe for Hydroponic Success (Cornell Controlled Environment Agriculture): the two single-salt recipes, their magnesium sulfate amounts and tanks, tomato magnesium targets, and calcium precipitating with sulfates and phosphates.
UC Agriculture and Natural Resources, Maintenance of Microirrigation Systems: fertilizer-water reactions and jar tests: gypsum precipitation from sulfate fertilizers in hard water, and testing before injection.

Rates and sources reviewed November 10, 2026.

Help choosing & next step

Not sure whether your plants need magnesium, or how to read a soil or leaf test? Email your plants, how they are grown, and any test results to questions@greenwaybiotech.com, or call (562) 351-5168, Monday to Friday, 9 AM to 3 PM Pacific, and we will work through it with you.

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