What is 4-4-4 fertiliser good for? NPK numbers explained

If you only need one bag for the whole garden, start with Organic All Purpose Fertiliser 4-4-4.

By Joe Barrington, founder of Dr Forest · Published September 2026

In short

A 4-4-4 fertiliser is a balanced feed: 4% nitrogen, 4% phosphate and 4% potash. It is good for mixed beds and borders, the vegetable garden before anything starts fruiting, pots at planting, and established shrubs and perennials: anywhere you want one feed for many plants and have not had a soil test. It is not the feed for fruiting tomatoes, and it is the wrong tool for fixing a single shortage.

What 4-4-4 fertiliser is good for, and where it stops

In pots, mix it through the compost at planting, at a rate set by how hungry the plant is:

Appetite	Mixed into the compost	Plants
Light and medium	5 g per litre	Peas and beans, roots, onions, woody herbs, established shrubs, potatoes, salad leaves, kale, leeks, soft fruit, most perennials
Heavy	Up to 10 g per litre	Tomatoes, courgettes, squash, chillies, the brassicas, dahlias

Once the plants are growing, top dress pots at 2 g per litre of pot volume every 4 weeks, or 2 to 3 g every 2 to 3 weeks for heavy feeders. Those are potting rates, not bed rates. On beds, borders and allotment plots, scatter 100 g per m², work it lightly into the top 5 to 10 cm and water it in. Repeat every 6 weeks in the growing season, up to three times a year. More on topping up pots in how to top dress, and full rates by plant are on the All Purpose 4-4-4 page. Notes for each plant are in how to grow 194 plants.

Fruiting tomatoes are the exception. Once the first truss has set, a tomato wants more potassium than nitrogen, so switch to a tomato feed such as Tomato 3-4-6. A bloom feed won't help: Bloom 2-8-4 has the same 4% potash as this bag. When and how much to feed them is in my guide to the best fertiliser for tomatoes.

Plants use less phosphate than nitrogen, so a bed fed 4-4-4 for years slowly builds up phosphate. After a few seasons, feed it less often. The same logic applies to a bed that is short of nitrogen alone: more 4-4-4 also adds phosphate and potash it doesn't need, so use a high nitrogen feed for leafy growth to correct that one shortage.

What the three numbers mean

Every bag of NPK fertiliser carries the same three figures in the same order. NPK stands for the chemical symbols of nitrogen, phosphorus and potassium. The label counts phosphorus as phosphate (P2O5) and potassium as potash (K2O), so the actual elements in a 4-4-4 come to about 1.7% phosphorus and 3.3% potassium.

Equal numbers make it a balanced feed, the sensible default when you haven't had a soil test. Pile on one nutrient and another can suffer: too much potassium makes it harder for the plant to take up magnesium. I gave All Purpose 4-4-4 equal numbers because feeding most plants mainly nitrogen gives sappy, leggy growth that is far more open to pest and disease pressure.

So I recommend one balanced feed. A garden holds many different plants, and most of them do well on the same bag. It is the best compromise.

Other ratios you'll see on the shelf:

• 7-7-7 (Growmore): balanced like 4-4-4, but more concentrated and mineral.
• 3-4-6 (tomato feed): more potash, for fruit.
• 2-8-4 (bloom fertiliser): low in nitrogen, for flowering.
• 5-3-5 (rose feed): a bit more nitrogen, for leaf and repeat flowers.
• 0-0-50 (sulphate of potash): potash only, for a known shortage.

For the rest of what is printed on the label, see how to read a fertiliser bag.

What the numbers don't tell you

That leaves 880 g in every kilo that the numbers don't describe. In a mineral blend it's mostly the rest of the salts plus some filler. In mine it's alfalfa meal, bone meal, seaweed, gypsum and the rest. That 88% is what separates one 4-4-4 from another.

Organic ingredients carry nutrients within plant or animal material. They generally have lower NPK percentages than concentrated mineral fertilisers because the nutrients come with that organic material, rather than as concentrated mineral salts.

My All Purpose 4-4-4 combines those organic ingredients with minerals. Its NPK describes the declared nutrient concentration; it doesn’t describe the whole blend.

Scorch happens when dissolved salts make the soil water strong enough to pull water out of the roots. More than half the nitrogen in my 4-4-4 comes from a nitrogen extract derived from molasses, and the rest mostly from alfalfa and flaxseed. It's held in proteins and amino acids, so far less of it is dissolved on day one. A double dose by mistake is unlikely to scorch, though it's still nitrogen and phosphate the bed didn't need.

What's in my 4-4-4

I formulate and blend mine from ten ingredients. Alfalfa meal is a third of the bag and the carbon backbone. Bone meal is 18%: it supplies most of the phosphorus, released slowly, and it means this blend isn't suitable for vegan gardening. The nitrogen extract is 18% and flaxseed meal 10%, then gypsum 6%, sulphate of potash 5.5% and kieserite 5%. Scottish seaweed, humic and fulvic acids and fermented biochar make up the last 4%.

Nutrient	Dr Forest 4-4-4	Supplied by
Nitrogen (N)	4.0%	Nitrogen extract, alfalfa, flaxseed, bone meal
Phosphorus (as P2O5)	4.0%	Bone meal, about 18% P2O5
Potassium (as K2O)	4.0%	Sulphate of potash (50% K2O), alfalfa, seaweed
Calcium (as CaO)	present, no figure declared	Gypsum, bone meal
Magnesium (as MgO)	present	Kieserite
Sulphur (as SO3)	present	Gypsum, kieserite, sulphate of potash
Trace elements	present	Scottish seaweed, fulvic acid

How long a 4-4-4 keeps feeding

Mixed into a pot at planting, my 4-4-4 feeds most plants for up to eight weeks. The nitrogen extract and alfalfa get going within days, while bone meal gives up its phosphorus over months, more slowly on chalky soil. Why it works that way, and why it sits idle in a cold spring, is in my guide to how slow-release fertiliser works.

So why not just buy a 7-7-7?

The 7-7-7 most people mean is Growmore, the Ministry of Agriculture's wartime mix: its November 1942 leaflet gives 7% nitrogen, 7% phosphate and 7% potash [1]. It's still on the shelves because its nitrogen is cheap. Per unit of nitrogen it beats anything in my range.

What it can't do is put plant material back in the soil. Westland's 2018 safety data sheet for its Growmore names one ingredient, limestone, at 40 to 50% of the bag [2]. Another brand's 2011 sheet lists sulphate of ammonia, superphosphate and sulphate of potash, with mineral filler and china clay [3]. At 100 g per square metre, my 4-4-4 puts about 65 g of plant material on the bed. The 57 g of Growmore that gives the same nitrogen adds none.

A 2024 review of 211 field studies worldwide found that swapping part of the mineral fertiliser for organic material gave richer soil life and about a third less nitrogen leaching, though swapping all of it cost yield [4]. If cheap nitrogen is all you need, Growmore does the job. If you also want organic matter going back into the soil, a 4-4-4 like mine is the better buy.

Related: Organic All Purpose Fertiliser 4-4-4 · Tomato 3-4-6 · Bloom 2-8-4 · High Nitrogen Fertiliser 13% N · Which fertiliser do I need? · the full range of organic fertilisers

Common questions

What is 4-4-4 fertiliser good for?

Mixed beds and borders, veg before it starts fruiting, pots at planting, and established shrubs and perennials. It is a balanced feed for when you want one bag for many plants and have not had a soil test. Switch to a tomato feed once tomatoes set fruit.

What do the numbers in 4-4-4 mean?

4% nitrogen, 4% phosphate (P2O5) and 4% potash (K2O) by weight, always in that order. That is NPK: nitrogen, phosphorus and potassium. The other 88% of the bag is what the numbers leave out.

What is a 4-4-4 fertiliser?

A balanced feed with 4% nitrogen, 4% phosphate and 4% potash by weight. I formulate and blend mine from organic ingredients, led by alfalfa meal, bone meal and a molasses-based nitrogen extract.

Is the Dr Forest 4-4-4 suitable for vegan gardening?

No. Bone meal is 18% of the blend, so it isn't suitable for vegan gardening.

How does it compare to Growmore 7-7-7?

Growmore is cheaper per unit of nitrogen, and on that measure it beats anything in my range. My 4-4-4 carries its nitrogen in plant material, so it also puts organic matter back and goes easier on soluble salt.

Can I use 4-4-4 on tomatoes?

Yes, until the first truss sets. Then switch to a tomato feed such as Tomato 3-4-6, because fruiting tomatoes want more potash than nitrogen.

Joe Barrington

Founder of Dr Forest. In Stockport, Joe formulates and blends his own feeds, All Purpose 4-4-4 among them.

Sources

1. Ministry of Agriculture (1942). National Growmore Fertilizer. Wartime leaflet, November 1942. Transcribed at dig-for-victory.org.uk
2. Westland Horticulture Ltd (2018). Safety data sheet: Growmore garden fertiliser, NPK 7-7-7. Revision 27 April 2018. gardenhealth.com (PDF)
3. Proctors (2011). Safety data sheet: Growmore 7:7:7. 29 November 2011. proctorsnpk.com (PDF)
4. Wang, X., Liu, M., Ciampitti, I.A., Cui, J., Fang, K., Zhao, S., He, P. and Zhou, W. (2024). Benefits and trade-offs of replacing inorganic fertilizer by organic substrate in crop production: a global meta-analysis. Science of The Total Environment 925: 171781. doi:10.1016/j.scitotenv.2024.171781