What is 4-4-4 fertiliser, and what is it good for?

The short NPK answer now lives on our page hub: What is 4-4-4 organic fertiliser? This post keeps the longer garden notes. If you only need one bag, start with All Purpose 4-4-4.

By Joe, Founder of Dr Forest · September 2026 · 8 min read

Edited 24 Sep 2026

Three identical numbers on a bag, all of them low. That combination puts more people off than anything else on the shelf.

A 4-4-4 fertiliser is 4% nitrogen, 4% phosphorus as P₂O₅ and 4% potassium as K₂O, by weight. Equal parts of the three nutrients plants draw on most heavily. A kilo carries 40 g of each. The rest is the material doing the carrying, and in a good blend it earns its place.

It is the feed to reach for when you do not know what your soil is short of, and it suits most of a garden: veg beds, fruit bushes, roses, shrubs, baskets and patio pots. Where it stops being the right answer is at the specific growth stages.

What separates one 4-4-4 from another, and from a mineral 7-7-7, is the other 88 per cent of the bag.

What the three numbers mean

Every fertiliser carries the same three figures in the same order, the NPK: nitrogen, phosphorus, potassium. Nitrogen is given as the element, phosphorus as P₂O₅ and potassium as K₂O, a hangover from how laboratories used to report an ash analysis. So a 4-4-4 puts 40 g of each into a kilogram, with 880 g of everything else. In a mineral blend most of that is inert filler. In this one it is alfalfa meal, bone meal, seaweed, gypsum and the rest.

Equal numbers make it a balanced feed, which matters most when you are working blind. Push nitrogen hard into a soil that had plenty already and you get soft leafy growth with little behind it. Push potassium hard and you can make magnesium harder to take up. A soil test is the honest way to find out what is short; most gardeners do not have one, and a balanced feed is the sensible default without it.

A low number does not mean a weak fertiliser

A 4-4-4 is roughly a third the concentration of a 12-12-12. Same nutrients into the same ground means three times the product weight: 200 g of 4-4-4, or 114 g of 7-7-7, or 67 g of 12-12-12, to put 8 g each of N, P₂O₅ and K₂O on a square metre.

Scorch is an osmotic problem — soluble salts raise the soil solution until water leaves the root. Most nitrogen here arrives as protein and amino nitrogen in alfalfa and flaxseed; microbes must open it first. Little is soluble salt on day one. You can put down twice as much 4-4-4 as you meant to and the worst is usually a fortnight of soft growth. The trade-off is bulk.

What a good 4-4-4 organic fertiliser has in it

The three numbers are the least interesting thing on the label. Ours is ten inputs. Alfalfa meal 33% — carbon backbone, N, K, amino acids. Bone meal 18% — about 18% P₂O₅ plus calcium; the slow half of the phosphorus, and the reason this blend is not suitable for vegan gardening. I would rather say so plainly than bury it. Nitrogen plant extract from molasses ~18%; flaxseed 10%; then gypsum 6%, sulphate of potash 5.5%, kieserite 5%; Scottish seaweed, humic/fulvic and fermented biochar make up the last ~4%.

Table 1. The secondaries carry no declared figure on this product, so none is given.

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

The 7-7-7 most people mean is Growmore — a wartime Ministry analysis (1942) kept for cheapness and uniformity ever since [2]. Per unit of nitrogen it beats anything I make. What it cannot do is put carbon-bearing material back.

Westland’s SDS lists mineral salts and fillers — ammonium sulphate, urea, phosphates, potassium chloride or sulphate, and inert sand or limestone among the options [3]. Three numbers on the bag; secondaries and traces undeclared.

At the same nitrogen, a square metre on Dr Forest 4-4-4 receives about 130 g of plant-derived input (alfalfa alone ~66 g) plus mineral and bone fractions. The same metre on mineral 7-7-7 receives none.

Buy 7-7-7 for the cheapest nitrogen you can spread. Buy 4-4-4 if you want that nitrogen attached to something.

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

Sort your plants by appetite. Light feeders take 5 g per litre in a soil mix and 2 g per litre as a top dress, every five to six weeks: peas and beans, roots, onions, woody herbs, established shrubs. Medium feeders take 7 to 8 g and 3 g on the same measures, every three to four weeks: potatoes, salad leaves, kale, leeks, soft fruit, most perennials. Heavy feeders take 10 g and 4 g, every two to three weeks in full growth: tomatoes, courgettes, squash, chillies, the brassicas, roses, dahlias. Containers count as heavy feeders whatever is in them. On open ground, allow 100 to 300 g per square metre every four to six weeks, worked into the top 5 to 10 cm. Quantities in full: how much all purpose fertiliser to use.

Now the honest limit. A tomato that has set its first truss in July wants considerably more potassium than nitrogen, and a 4-4-4 hands it the same of each. For that the Tomato 3-4-6 or a bloom feed is the right tool. Treat 4-4-4 as the base charge for the season, then switch when the plant switches. More on that split in best fertiliser for tomatoes and in the best fertiliser for a vegetable garden.

How long a 4-4-4 keeps feeding

A soil-mix charge feeds most plants for up to eight weeks. Inside that, the inputs run at different speeds: the nitrogen extract and the alfalfa are doing something within days, whilst bone meal and gypsum release over eight to twelve weeks. The feed arrives steadily instead of all at once, which is what you want in a base charge.

That spread is normal for organic materials. A survey of 113 published incubation datasets modelled nitrogen release from organic amendments and found a wide range: between 50 and 65% of the nitrogen in feather meal was predicted to be in mineral form after 100 days at 25 °C with optimal moisture, whilst yard waste compost released under 10% across a growing season.⁸ What a material does depends on what it is made of, the subject of organic slow release fertiliser.

If the compost you mixed it into was already rich, expect to reapply after two to four weeks rather than eight. For surface feeding see how to top dress like a pro; for the old shop-shelf standards, Growmore vs blood, fish and bone.

Related: Organic All Purpose Fertiliser 4-4-4 · Tomato 3-4-6 · Organic Nitrogen Fertiliser · See the full range of organic fertilisers

Buy the balanced bag first, learn what your beds do with it across a season, then buy the specific feeds once you know what your plants want.