Rose & Flower Fertilisers

Calcium and potassium, not phosphorus

A fertiliser for roses should be built on calcium and potassium in balance. Rose feeding in Britain has been built on high phosphorus for about seventy years, and the trial data never really supported it. What repeat-flowering roses actually run on is calcium and potassium in balance, with enough nitrogen to keep the foliage working hard enough to fuel the next flush. That is what these blends are built around.

Rose feed, rose food, rose fertiliser: the same thing under three names. Everything here is granular and slow release, so one application keeps working for weeks instead of asking you to remember a bottle every Saturday.

Start here

Rose & Shrub Fertiliser 5-3-5 is the core of it. Slow release, hand-blended in Stockport, formulated for repeat flowering, depth of colour and fragrance rather than one big early flush. For most rose beds that one bag is the whole job, and if you are still comparing, the best organic fertiliser for roses and flowers answers the question directly.

Bloom 2-8-4 is the higher-phosphorus option, for annuals, perennials and ornamentals where you want maximum flower output in a shorter window rather than a long repeat season.

Feeding through the year

First feed in early spring as the buds break, then again after the first flush has finished, to fuel the next one. Stop feeding by late summer so the wood hardens off before winter. Slow-release granular feeds suit this pattern well, because a single application keeps working for weeks rather than washing through in a fortnight, and when to feed roses, month by month sets the same pattern against the calendar.

When to feed roses: spring, summer and autumn

Timing is where most rose feeding goes wrong, and it is easier to get right than the folklore suggests. Three moments matter and one of them is a moment to stop.

Spring

The first feed goes on as the buds break and the soil has begun to warm, usually somewhere between late March and mid-April depending on how far north you are and what the winter did. Feeding roses before there is any root activity to take the nutrients up mostly feeds the weather. A granular feed worked lightly into the surface and watered in is doing its job before the first leaves are fully out.

Summer

The second feed goes on once the first flush is over and the spent flowers have been deadheaded. This is the one that pays for itself, because a repeat-flowering rose is building the next flush while it is still finishing the last one, and that costs it potassium in particular. On a long season with a third flush, a light feed after the second flush is reasonable. Rates are on each product page.

Autumn and winter

Stop by late summer. Nitrogen applied into autumn pushes soft growth that will not harden before the first frosts, and soft growth going into a British winter is a liability. Autumn is for the soil rather than the plant: mulch, and if the bed needs it, a calcium and potassium amendment — micronised gypsum covers the calcium half — worked in over winter so it is in place when the buds break. There is no useful winter rose feed, and anyone selling you one is selling you a mulch with a better name.

The amendments worth adding

• Alfalfa meal pellets. The oldest trick in rose growing, and the one with the most interesting chemistry behind it. Organically grown alfalfa carries triacontanol, a naturally occurring growth regulator, alongside slow organic nitrogen. I went looking for the trial behind the folklore and wrote up what I actually found.
• Sulphate of potash. Chloride-free potassium for flower size and colour, with no chloride load on the soil.
• Polyhalite. Potassium, calcium, magnesium and sulphur from a single Yorkshire-mined granule. Useful when you want potash and calcium together rather than separately. Which of the two to choose.
• Mycorrhizal fungi. Dusted onto the roots when you plant a new rose. Roses form mycorrhizal associations readily, so this is one of the cases where an inoculant earns its place.

Flower fertiliser for beds, borders and containers

Roses are the reason most people arrive here, but the same reasoning applies across a flower bed. A flower fertiliser needs to fund a long, repeated cycle of bud, bloom and set-down, and that is a potassium and calcium job with steady nitrogen behind it rather than a phosphorus one. Both blends work on dahlias, sweet peas, hardy geraniums, mixed herbaceous borders and container displays. Where you want the biggest possible show over a short window, from bedding or annuals in pots, Bloom 2-8-4 is the one. Where you want a season of repeat performance, Rose & Shrub 5-3-5 is.

Rose feed UK: why calcium and potassium

Every product here carries a full ingredient list on the label. The reason the range is so specific about calcium and potassium is that British rose advice has been repeating the same high-phosphorus habit for decades without much behind it, and it seemed worth checking. Where the evidence for a traditional practice is thin, you will find it said so on these pages rather than glossed over.

Hydrangeas, camellias and the other acid-lovers have their own page at Hydrangea & Ericaceous Feed; the straight potassium sources are compared in Potash & Potassium Fertilisers, and the higher-phosphorus options in Phosphorus Fertilisers.

Common questions

Does Epsom salt help roses?

Epsom salt for roses works sometimes, on soils genuinely short of magnesium, and not at all on soils that are not. It is one of the most repeated tips in British gardening and one of the least supported by trial evidence. Epsom salt is magnesium sulphate, 17.7% Mg, so it addresses magnesium and nothing else, as does kieserite, the mined form of the same magnesium sulphate: it will not give you more flowers on a soil that already has enough. Here is what the trials show.

What is the difference between rose feed and rose food?

Nothing at all. Rose feed, rose food and rose fertiliser are the same product described by three different habits of speech. What does differ is the formulation behind the name, and what to look for in a rose fertiliser is worth reading before you buy.

What is the difference between Rose & Shrub 5-3-5 and Bloom 2-8-4?

Rose & Shrub 5-3-5 is balanced towards repeat flowering, fragrance and colour across a long season. Bloom 2-8-4 carries far more phosphorus and suits annuals, perennials and ornamentals where you want the biggest possible display in one go. What the NPK numbers on a rose feed actually mean goes through the reasoning behind both.

How often should I be feeding roses?

Less often than most people expect. These are slow-release granular feeds, so the spring and post-flush applications described above cover a normal season. Feeding roses more frequently than the product page states does not produce more flowers; it produces more leaf. If a rose is not flowering at all, feeding is rarely the cause, and eight commoner reasons roses will not flower covers the likelier ones.

Will it scorch my roses?

Not at the stated rate. These release gradually rather than dumping soluble salts at the root in one go, which is what causes scorch.

Can I feed a newly planted rose?

Yes, and the more useful thing at planting is the mycorrhizal inoculant dusted straight onto the roots, where it is in contact with them; planting a bare-root rose properly covers the rest of the job. Feed properly from the following spring, once the plant has roots out into the soil to make use of it.

Can I use these on other flowering plants?

Yes. Both blends work across mixed flower beds, borders, dahlias, sweet peas and container displays, though roses grown in pots have a watering and feeding rhythm of their own. Rates are on each product page.

Do you make a liquid rose feed?

The rose range is granular, because slow release matches how a repeat-flowering rose spends nutrients across a season. If you prefer to feed with a liquid, or want something that acts faster on a plant already in flower, the liquid fertilisers cover that — the high-potash 3-2-6 liquid feed is the closest thing to a liquid rose feed — and the crop-specific granular blends are in crop-specific fertilisers.

When should I stop feeding?

Late summer. Feeding into autumn pushes soft new growth that will not harden before the first frosts. What roses do want at that point is set out in the autumn care guide.