All-Purpose Houseplant Food 27-9-18 with Chelated Micronutrients
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Per lb vs 1 Pound
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$ 24.99
$ 24.99
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$ 38.99
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The 2 x 25 lb size ships as two separate 25 lb bags.
All-Purpose Houseplant Food 27-9-18 is a water-soluble powder for feeding foliage houseplants at every watering. Its 3:1:2 ratio of nitrogen to phosphate to potash follows University of Florida IFAS foliage-plant research, and a level ½ teaspoon (about 2.1 g) per gallon gives 150 ppm nitrogen, 50 ppm phosphate and 100 ppm potash: the continuous-feed levels that research suggests, all from one dose.
It is a continuous-feed product: you mix a weak solution and use it each time you water, at a strength set by how fast your plants are growing. It carries six micronutrients, with iron, manganese, zinc and copper chelated. It contains no calcium, magnesium or sulfur, so plants in mixes without dolomitic lime, or watered with RO or rain water, need those from another source.
27-9-18 Total nitrogen, available phosphate (P₂O₅) and soluble potash (K₂O), an exact 3:1:2 ratio with no filler
½ tsp per gallon At each watering in active growth; ¼ tsp in medium or low light, ⅛ tsp in winter
No Ca, Mg or S Supply them separately where your mix or water lacks them. See the directions
27%: 3.5% nitrate nitrogen and 23.5% urea nitrogen
Available phosphate (P₂O₅)
9%
Soluble potash (K₂O)
18%
Boron (B)
0.02%
Copper (Cu)
0.014%, all of it chelated copper
Iron (Fe)
0.11%, all of it chelated iron
Manganese (Mn)
0.05%, all of it chelated manganese
Molybdenum (Mo)
0.0015%
Zinc (Zn)
0.05%, all of it chelated zinc
Ingredients and specifications
Specification
Detail
Derived from
Urea, potassium nitrate, monopotassium phosphate, iron DTPA, manganese EDTA, zinc EDTA, copper EDTA, boric acid and sodium molybdate
Chelating agents
DTPA (iron); EDTA (copper, manganese, zinc)
Labeled use
Continuous liquid feed: dissolved in water and applied at every watering
Form
Water-soluble powder. No filler, wetting agent or anti-caking additive
Not supplied
Calcium, magnesium and sulfur. No chloride-containing ingredients
At ½ level teaspoon (about 2.1 g) per US gallon
150 ppm N, 50 ppm P₂O₅ and 100 ppm K₂O (on the elemental basis, about 22 ppm phosphorus and 83 ppm potassium), with about 0.61 ppm iron, 0.28 ppm manganese, 0.28 ppm zinc, 0.11 ppm boron, 0.08 ppm copper and 0.008 ppm molybdenum
Package sizes
1 lb (454 g), 2 lb, 5 lb, 10 lb, 25 lb, and 50 lb as 2 × 25 lb
The ppm figures are worked from the guaranteed analysis: ppm of a nutrient = grams per US gallon × its percentage × 2.642. Nitrogen at ½ teaspoon per gallon is 2.10 × 27 × 2.642 = 150 ppm. The teaspoon measures on this page assume a level, loosely filled measuring teaspoon; for the most accurate dose, weigh the grams.
Best uses & benefits
Choose it when you water foliage houseplants regularly and want one weak feed you can use at every watering, with the strength set by light and season.
Foliage houseplants in potting mix
Pothos, philodendron, peace lily, dracaena, ferns and other plants grown for their leaves. University of Florida IFAS foliage research at its Apopka center suggests a 3:1:2 fertilizer for foliage plants in soilless media, and this grade holds that ratio exactly.
Feeding at every watering
The label directions are concentrations for each watering, not a monthly dose. That suits people who water on a routine and would rather not track feeding days.
Plants in different light
One powder covers a bright window and a dim corner: ½ teaspoon per gallon for plants in active growth in bright indirect light, ¼ teaspoon for medium or low light, ⅛ teaspoon in winter or when growth slows.
Offices, studios and interiorscapes
The IFAS interior-maintenance report recommends 3-1-2 ratio fertilizers for maintaining foliage plants indoors, noting their lower cost per unit of nitrogen and lower soluble salts.
Where it is a poor fit
Mixes without dolomitic lime, or RO, distilled or rain water, with nothing else added. This food has no calcium, magnesium or sulfur. Add them as described under Calcium, magnesium and sulfur, or choose a mix limed with dolomite.
Feeding once a month at full strength. The label gives only continuous-feed directions, applied at every watering.
Hydroponic reservoirs and fertilizer injectors. This page gives no reservoir or injector stock directions. For hydroponics, see Grow Green 4-2-6 and the rest of Greenway’s four-part system.
Cool, cloudy winters with a nitrate-only goal. Most of the nitrogen is urea. University of Tennessee Extension advises keeping ammonium and urea under 40% of the nitrogen in winter greenhouse production; this powder cannot do that, which is why its winter rate is a quarter of the summer rate. See How it works.
Plants with special feeding needs, such as carnivorous plants. The label directions are set by light and growth, not by species, and the research behind them is foliage-plant work.
Application rates & directions
Dissolve the powder in water and apply it to moist potting mix at every watering. Choose the line that matches how your plants are growing right now, and move down a line as light or temperature drops.
Label directions
All-Purpose Houseplant Food 27-9-18 label directions, per US gallon of water at each watering
Growing condition
Per gallon
Weight
ppm N-P₂O₅-K₂O
Research basis
Active growth, bright indirect light, spring and summer
½ level teaspoon
2.10 g
150-50-100
UF/IFAS RH-90-1 suggested continuous-feed levels
Medium or low light; maintenance
¼ level teaspoon
1.05 g
75-25-50
UF/IFAS RH-91-7: interior rates fall with light
Winter, cool rooms, slow growth
⅛ level teaspoon
0.53 g
38-13-25
UF/IFAS RH-91-7: cut rates at least 50% in cool conditions (this is a 75% cut)
Water first if the mix is dry. UConn’s Home and Garden Education Center advises always applying fertilizer to already moist potting soil to avoid root damage. Dissolve the powder fully before it touches the plant; never sprinkle it dry onto the mix.
Below about 75 foot-candles, a dim interior spot, the IFAS interior-maintenance report notes that the natural breakdown of peat and bark in the potting mix can supply enough nitrogen, so plants there need very little added feed. Use the lowest line, and watch the plant rather than the calendar.
Batch sizes
Grams of All-Purpose Houseplant Food 27-9-18 for common batch sizes at each label line
Water
Active growth (½ tsp per gallon)
Medium or low light (¼ tsp per gallon)
Winter (⅛ tsp per gallon)
1 quart
0.53 g (⅛ tsp)
0.26 g
0.13 g
½ gallon
1.05 g (¼ tsp)
0.53 g (⅛ tsp)
0.27 g
1 gallon
2.10 g (½ tsp)
1.05 g (¼ tsp)
0.53 g (⅛ tsp)
2 gallons
4.20 g (1 tsp)
2.10 g (½ tsp)
1.05 g (¼ tsp)
5 gallons
10.5 g (2½ tsp)
5.25 g (1¼ tsp)
2.65 g (⅝ tsp)
1 liter
0.55 g
0.28 g
0.14 g
10 liters
5.55 g
2.77 g
1.40 g
Teaspoons are shown only where they come out to a measurable fraction of the label measure. For small batches, mix a full gallon and keep the rest for the next watering, or weigh on a scale that reads to 0.01 g.
Calcium, magnesium and sulfur
This food supplies none of them. University of Florida IFAS notes that dolomite in potting media provides calcium and magnesium, and that if it is not used, those elements should be supplied some other way. Dolomitic lime supplies both; calcitic lime supplies calcium only.
Your mix contains dolomitic lime (check the bag) and you water with tap water: no change is usually needed.
Your mix is unlimed or limed with calcitic lime, or you water with RO, distilled or rain water: also feed calcium from Calcium Nitrate, and magnesium and sulfur from Epsom Salt for Plants (magnesium sulfate). University of Tennessee Extension calls a calcium-to-magnesium ratio of 3:1 to 5:1 desirable. Use the amounts on each product’s page, or email us your mix and water for help.
Combine them only in the watering can, one at a time. Fill the can with water, dissolve each product fully before adding the next, then water. University of Tennessee Extension explains that calcium and magnesium fertilizers typically cannot be mixed with phosphate and sulfate fertilizers while concentrated, but that once each is diluted to its final strength, all fertilizers are compatible. Never mix the dry powders together, and never combine them in a concentrated stock: Epsom salt reacts with the urea in this food in the dry state and turns damp, and calcium nitrate draws in moisture.
Keeping salts in check
Every fertilizer adds salts to a pot. UConn lists browning roots and leaf tips, wilting, poorly shaped leaves and a white crust on the pot rim as signs of over-fertilizing, and notes that leaching the pot with plenty of water reduces excess fertilizer salts. Water so that some drains from the bottom, empty the saucer, and if you see those signs, leach the pot with plain water and drop to a lower line.
How to use All-Purpose Houseplant Food 27-9-18
Pick your line. Bright light and new growth: ½ teaspoon per gallon. Medium or low light: ¼ teaspoon. Winter or slow growth: ⅛ teaspoon.
Measure and dissolve. Add a level, loosely filled measure, or the grams from the table, to room-temperature water and stir until fully dissolved.
Add calcium and magnesium if you need them. If your mix has no dolomitic lime or you use RO or rain water, dissolve calcium nitrate and Epsom salt in the same can, one at a time, after this food is fully dissolved.
Water moist mix. If the mix is bone dry, water it lightly first. Then water with the solution until a little drains out, and empty the saucer.
Repeat at each watering. Move down a line as days shorten or growth slows, and leach with plain water if you see salt crust or tip burn.
Calculator & choosing a size
Formula. Grams of powder = US gallons of water × 2.10 (active growth), × 1.05 (medium or low light) or × 0.53 (winter), or liters × 0.555, × 0.277 or × 0.140. A 1 lb bag (454 g) makes about 215 gallons of solution at ½ teaspoon per gallon.
About how many US gallons of feeding solution each bag makes at each label line
Bag
Active growth, 2.10 g per gallon
Medium or low light, 1.05 g per gallon
Winter, 0.53 g per gallon
1 lb
215 gallons
431 gallons
855 gallons
2 lb
431 gallons
863 gallons
1,711 gallons
5 lb
1,079 gallons
2,159 gallons
4,279 gallons
10 lb
2,159 gallons
4,319 gallons
8,558 gallons
25 lb
5,399 gallons
10,799 gallons
21,395 gallons
Worked examples.
A 1-gallon watering can, mixed twice a week for 12 weeks of spring growth (24 batches at ½ teaspoon): 24 × 2.10 = 50.4 g. The 1 lb bag covers it many times over.
A 5-gallon bucket for a sunroom collection, mixed weekly for 26 weeks at ½ teaspoon per gallon: 130 gallons × 2.10 = 273 g. The 1 lb bag covers it.
An office interiorscape using 25 gallons a week for 52 weeks at ¼ teaspoon per gallon (medium light): 1,300 gallons × 1.05 = 1,365 g, about 3.0 lb. The 5 lb bag is the smallest single bag that covers it.
The calculator below asks how much water you mix at a time, how many batches you will mix, and how your plants are growing. It applies the matching label line, gives the grams for each batch and in total, and recommends the smallest bag that covers it, 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 tables and formula above to choose a size.
How All-Purpose Houseplant Food 27-9-18 works
The ratio. Researchers at the University of Florida IFAS Central Florida Research and Education Center in Apopka suggest a 3:1:2 ratio fertilizer for foliage plants grown in soilless media (Conover and Poole, RH-90-1). Their interior-maintenance report recommends 3-1-2 ratio fertilizers for plants kept indoors and notes that plants grow equally well on 1-1-1 fertilizers such as 20-20-20, but that 3-1-2 costs less per unit of nitrogen and leaves lower soluble salts (RH-91-7). A light-intensity trial on six foliage plants found that formulation did not change growth and concluded that 3:1:2 should be used instead of 1-1-1, to limit excess phosphate and potash (RH-90-16).
One dose, three targets. RH-90-1 suggests 150 ppm nitrogen, 50 ppm phosphate (P₂O₅) and 100 ppm potash (K₂O) for continuous application. That target is itself 3:1:2, so a 27-9-18 lands on all three at one dose: 2.10 g per gallon. A grade with a different ratio could match the nitrogen target but not the other two at the same time.
The nitrogen. About 87% of the nitrogen is urea and 13% is nitrate, from potassium nitrate. An IFAS summary of nitrogen-form research found little or no difference among many foliage plants, called ammonium and urea, alone or combined, logical choices for many foliage plants, and found that peacock plants fed mostly nitrate developed leaf damage (Steinkamp, Conover and Chase, RH-92-27). University of Tennessee Extension adds two cautions: high ammonium can be toxic during cold, cloudy conditions, and fertilizers with ample ammonium or urea tend to lower the pH of the growing medium. That is why the winter line is ⅛ teaspoon, and why leaching the pot with plain water now and then is part of the routine.
The micronutrients. Iron, manganese, zinc and copper are chelated, iron with DTPA and the other three with EDTA. A chelate holds the metal in a dissolved form so it stays in solution in the watering can. Iron is the largest of the six; boron and molybdenum are present at trace levels.
What it leaves out. Calcium cannot travel with phosphate and sulfate in a concentrated product without forming insoluble compounds, and magnesium sulfate reacts with urea in a dry blend, so this powder carries neither. Dolomitic lime in the potting mix normally supplies both; where it does not, add them in the watering can as described in the directions.
This describes the research behind the formula and nutrient behavior in general; it is not a trial of this finished product.
Compare your options
Match the product to what your plants and potting mix are missing.
All-Purpose Houseplant Food 27-9-18 compared with other Greenway options for container plants
Option
Supplies
Choose it when
Limitation
All-Purpose Houseplant Food 27-9-18, this product
Nitrogen, phosphate and potash at 3:1:2, with six micronutrients
You feed foliage houseplants in potting mix at every watering
No calcium, magnesium or sulfur; continuous-feed directions only
Dolomite: calcium and magnesium built into a potting mix you blend yourself.
Same watering can, never the same scoop. Dissolve this food fully in the can, then dissolve calcium nitrate, then Epsom salt, one at a time, and water. Do not mix the dry powders, store them together, or combine them in a concentrated stock solution. Keep the scoop for this food dry and use it for nothing else.
Handling, storage & limitations
Storage. Keep the pouch sealed in a cool, dry place and close it tightly after every use. The blend draws in moisture from humid air. A caked powder still dissolves completely, but caking means moisture got in.
Never dry-mix. Do not add other fertilizers to the pouch or scoop. Epsom salt reacts with the urea in this food and turns the powder damp, and calcium nitrate draws in moisture.
Oxidizer. It contains potassium nitrate, an oxidizer. Keep it away from heat, flames and combustible materials.
Use limits. Use it dissolved in water, at the label lines, on moist potting mix. Do not apply dry powder to plants or soil.
Children and pets. Keep it out of reach of children and pets. If it gets in the eyes, rinse with plenty of clean water. If swallowed, call Poison Control at 1-800-222-1222.
Frequently asked questions
How much do I use per gallon?
A level ½ teaspoon (about 2.1 g) per gallon at each watering for plants in active growth in bright indirect light, which gives 150 ppm nitrogen, 50 ppm phosphate and 100 ppm potash. Use ¼ teaspoon (1.05 g) in medium or low light and ⅛ teaspoon (0.53 g) in winter or when growth slows. For other volumes, use about 0.55 g per liter at the active-growth line.
Do I really feed at every watering?
Yes. This is a continuous-feed product: every direction on the label is a weak concentration meant for each watering, not an occasional strong dose. Lower the strength as light and growth drop rather than skipping waterings with fertilizer.
What changed from the 21-7-14 version?
The earlier 21-7-14 carried magnesium as Epsom salt. In a dry blend, the urea in the formula reacts with Epsom salt and releases water, which can leave the powder damp or liquid in the bag. The 27-9-18 formula removes the Epsom salt, so it contains no magnesium or sulfur, and keeps the same 3:1:2 ratio at a higher analysis. Its dose is ½ teaspoon per gallon at every watering. If you have a 21-7-14 bag that has turned damp or liquid, do not use it; email questions@greenwaybiotech.com.
Why is there no calcium, magnesium or sulfur?
Calcium forms insoluble compounds with phosphate and sulfate when concentrated, and magnesium sulfate reacts with urea in a dry powder, so neither can share this bag. Potting mixes limed with dolomitic lime supply calcium and magnesium. If your mix is unlimed or limed with calcitic lime, or you water with RO, distilled or rain water, also feed calcium nitrate and Epsom salt, at about 3 to 5 parts calcium to 1 part magnesium.
Can I mix it with calcium nitrate or Epsom salt?
Yes, in the watering can, once each is dissolved. Fill the can with water, dissolve this food fully, then dissolve each of the others one at a time before watering. University of Tennessee Extension explains that calcium and magnesium fertilizers typically cannot be mixed with phosphate and sulfate fertilizers while concentrated, but that once diluted to their final strength, all fertilizers are compatible. Never mix the dry powders or make a concentrated stock of them together.
Is urea nitrogen all right for houseplants?
For most foliage plants, yes. A University of Florida IFAS summary of nitrogen-form research found little difference among many foliage plants and called ammonium and urea logical choices for fertilizing them; peacock plants fed mostly nitrate developed leaf damage. University of Tennessee Extension cautions that high ammonium can harm plants in cold, cloudy conditions and that urea tends to lower the pH of the mix over time, which is why the winter line is a quarter of the summer line and why occasional leaching helps.
Should I keep feeding in winter or in low light?
At a lower strength. Use ¼ teaspoon per gallon in medium or low light and ⅛ teaspoon in winter or when growth slows. University of Florida IFAS research on interior plants recommends cutting rates at least in half in cool conditions, and notes that in very dim spots the potting mix itself can supply most of the nitrogen a plant uses.
How do I avoid fertilizer burn and salt buildup?
Apply the solution to moist mix, never to bone-dry mix, as UConn advises, and let a little drain out each time you water. Browning leaf tips or roots, wilting, distorted new leaves, or a white crust on the pot rim are signs of excess fertilizer salts. If you see them, leach the pot with plenty of plain water and drop to a lower line.
Can I use it on flowering houseplants or succulents?
The label directions are set by light and growth rate, not by plant type, and the research behind the formula was done on foliage plants. For flowering houseplants in good light, the active-growth line applies. Slow growers such as succulents and cacti spend much of the year in slow growth, so the lower lines usually fit them.
Can I use it in hydroponics or a fertilizer injector?
This page gives directions only for mixing in a watering can. It contains no calcium or magnesium, so on its own it is not a complete reservoir nutrient. For hydroponic systems, Greenway’s four-part system is built for reservoirs. For injector use, email questions@greenwaybiotech.com.
How should I store it, and what if it cakes?
Keep the pouch sealed in a cool, dry place and close it right after each use, because the blend draws in moisture from humid air. Never add other fertilizers to the pouch. A caked powder still dissolves completely, but caking means moisture got in, so check the seal.
Related guides & articles
For this product, use the label directions, calculator and storage guidance on this page. For help fitting it to your plants, potting mix and water, email questions@greenwaybiotech.com with what you grow, the mix you use, and whether you water with tap, RO or rain water.
Where the rates and statements on this page come from
The guaranteed analysis, ingredients and directions come from the product label; the publications below supply the research and handling context noted beside each, without evaluating or endorsing this product.
Not sure which line fits your plants, or whether your mix needs calcium and magnesium? Email what you grow, your potting mix, and your water source to questions@greenwaybiotech.com, or call (562) 351-5168, Monday to Friday, 9 AM to 3 PM Pacific.
Every order carries a 90-day satisfaction guarantee, and we pack and ship from Madera, California. You can also choose a size from the size selector at the top of this page.
Greenway Biotech, Inc. is a family-owned company that has made specialty fertilizers in California since 1989, today in Madera.
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