The Best Buxus Fertiliser for UK Box Hedges

Why does box need a specific fertiliser?

Two reasons. Box is a slow, dense grower that holds its leaves for several years, so it wants steady, low-level feeding rather than a growth spurt. And box is unusually prone to magnesium deficiency, which is what turns a hedge that yellow-bronze colour people often mistake for disease.

A general-purpose high-nitrogen feed does the opposite of what you want: fast, soft growth with thin cell walls, which frost damages and blight colonises easily. It is a real risk rather than a theoretical one — the year I fed a hedge with lawn-grade fertiliser I got the worst blight I have ever had.

When should you feed box?

How much do you need?

The 500 g pack covers about 10 m² of box, which suits a few balls or a short run of low hedge. For anything more than a couple of metres of established hedging the 5 kg works out considerably cheaper per square metre, and it keeps perfectly well in a dry shed between seasons.

Measure the surface area of the hedge rather than its length — a 10 m run of hedge that is a metre deep and a metre tall is a lot more box than 10 m of a low edging.

Feeding a hedge back after caterpillar damage

A defoliated plant has lost the machinery it uses to make food, so it is rebuilding from stored reserves. Feeding it well is the single biggest thing you can do to speed that up, after making sure the caterpillars are actually gone.

1. Confirm the infestation is over first

   Feeding a hedge that still has caterpillars on it just gives them fresh growth to eat. Check for fresh frass before you start — see the identification guide.

2. Prune out anything actually dead

   Scratch the bark with a thumbnail. Green underneath means alive. Brown all the way through means dead, and it should come out so the plant stops spending energy on it.

3. Granular feed in spring, then again in midsummer

   Water it in if the spring is dry — granules sitting on dry soil do nothing.

4. Add a foliar feed every four to six weeks

   This is where foliar feeding earns its place: the plant can take nutrients in through what leaf it has left, without waiting for root uptake.

5. Mulch, and then be patient

   A 5–8 cm layer of well-rotted compost around the base. Then leave it alone — do not clip until it has substantially recovered.

What about blood, fish and bone?

It is a perfectly reasonable slow-release feed for box and considerably cheaper. What it does not give you is magnesium, so if your hedge is showing the yellow-bronze cast it will not fix it. A light dressing of blood, fish and bone in early spring plus Epsom salts for magnesium is a genuine budget alternative to a proprietary Buxus feed.

The reason I use a Buxus-specific product is convenience rather than magic: the balance is already right and I cannot get it wrong.

Signs you are feeding wrong

• Yellow-bronze leaves overall — magnesium deficiency. Common on box, and the main thing a Buxus-specific feed addresses.
• Pale, sparse growth — underfed, or the granules were never watered in.
• Fast, soft, floppy growth — too much nitrogen. Stop, and switch to a balanced feed next season.
• Yellowing only on the lower inner leaves — usually shade and airflow rather than nutrition. Thin the hedge instead of feeding it more.

Frequently asked questions