NPK is the easy part. The cation balance underneath is what makes a blend.

A lot of gardening advice is built on ideas that were disproved years ago and still get followed anyway. Roses are the easy example. High-phosphorus rose feeds are still sold, and still widely recommended, mostly on the strength of tradition. When I went through the literature myself, I found two peer-reviewed trials where the best yield actually came from the lowest phosphorus level they tested. Roses respond far more to a good calcium and potassium balance than to extra phosphorus, and our Rose & Flower 5-3-5 is built around that. That was the point it really clicked for me: research everything, and look for solid backing in the studies before an idea goes anywhere near a blend.

So before I make any blend, I read the trial data on what the plant actually needs, then work back to the ingredients. Every Dr Forest organic fertiliser starts from a target balance of calcium, magnesium and potassium. The NPK on the front of the bag is the last number to land, not the first.

That balance is what separates a feed that grows fruit you can taste from one that just bulks the plant out. Most of our crop blends sit around a 3:1:3 balance of calcium to magnesium to potassium, the figure that comes up most often in the research on fruit quality.

Almost none of the organic feeds you can buy off the shelf are built this way. Fish, blood and bone is the classic example: plenty of N-P-K, no attention paid to the calcium, magnesium and potassium balance underneath. They tend to be short on magnesium, and when magnesium runs low the plant can't make proper use of the potassium it's given, so the quality never really comes through.

There is also an old idea that your soil has to hit one perfect calcium-to-magnesium-to-potassium ratio. It has been tested for decades and doesn't hold up, so we don't chase it. The balance we care about is the one we feed the plant for quality, rather than trying to force your soil to a magic number. What's on the bag is what's in the bag, and the maths is on every product page.

Where a blend is doing something unusual, we say so. The Late Bloom (0.2-5-10) is deliberately low in nitrogen and high in potassium because its job is ripening rather than leafy growth. The Cal-Mag is there to correct deficiencies rather than to feed as a base.

How the guides and articles on this site get made.

Everything I publish here — the growing guides, the blog posts, the science notes on each product page — starts in the same place as the fertiliser: with the research. I read the trial data first, then write.

I use AI to help draft and structure, so I can get from my notes and the source papers to a working draft faster. Then I do the part that counts. Every figure gets checked against the original paper, anything that doesn't hold up gets corrected, and the whole thing gets rewritten into my own words before it goes live. The expertise, the formulations and the final call are mine. If a claim can't be stood up against a credible source, it doesn't get published.

Every claim on the site is checked against its source before it goes live — by me.

If you ever spot something that looks wrong, email me and I'll put it right. My address is at the bottom of this page.