Which fertilizer should you use for roses, and when?

When to fertilize roses

Feed a rose (Rosa) during active spring and summer growth, never during winter dormancy. In its UK calendar, the Royal Horticultural Society (RHS) places the first feed in March or April, before flowering, and the second in midsummer, after the first flush, especially for repeat-floweringA rose that flowers repeatedly during the growing season because it blooms on the current year's growth. varieties¹. The Société française des roses (SFR) gives its second feed in late June or early July in France, using the same fertilizer as in spring². Elsewhere, follow local growth and flowering rather than those months alone.

The first feed follows pruning. In late winter, the SFR lightly digs around the base and adds compost and a suitable rose fertilizer². In the source's Northern Hemisphere calendar, slower dry organic fertilizers go on from February-March, mineral fertilizers in March-April³. Match these late-winter and spring stages to local conditions.

Stopping matters as much as starting. For pots, the RHS advises against feeding after August in its UK calendar: the tender shoots it encourages are vulnerable to cold⁴. Few plants, it notes, need fertilizer during winter³. Use approaching cold and the end of active growth as the local cutoff.

Which fertilizer should you choose?

Rose fertilizer or a balanced fertilizer is enough in the garden. The RHS calls for either, scattered on the soil around the base¹. To read a label, look at its three numbers, the NPKA fertilizer's nitrogen (N), phosphorus (P), and potassium (K) content, in that order, expressed as percentages by weight.:

• Nitrogen (N) supports leaves and stems;
• phosphorus (P) supports roots and shoots;
• potassium (K) supports flowering and cold resistance³.

For container roses, this is why the RHS switches from a balanced liquid feed to a high-potassium fertilizer, such as tomato feed, as soon as buds form¹. Too much nitrogen has the opposite effect: leaves at the expense of flowers⁵.

Form	Action	Use for roses
Organic granules (bone, blood, and fish meal, poultry manure)	Slow, low concentration3	In the garden in February-March in the source climate; match local late winter3
Mineral granules, balanced or rose fertilizer	Faster3	In the garden in March-April, then summer in the source climate; follow local spring growth and flowering1
Liquid fertilizer	Fast, ideal for pots3	In pots, every fifteen days during active growth1
Slow-release fertilizer	Coated, released gradually3	In pots at planting, top-dressing, or repotting6
Well-rotted manure or compost	Feeds soil, retains moisture1	As mulch, 10 cm (4 in) away from stems1

In the ground or in a pot: how often?

In the ground, feed twice a year at 70 g of fertilizer per square meter (0.23 oz per sq ft). This is the RHS rate, scattered around the base¹. On poor soil or a poorly growing rose, a balanced granular fertilizer may also be added¹. Then mulch with well-rotted manure or compost, leaving a clear 10 cm (4 in) circle around the stems¹.

Container mix loses nutrients quickly. The RHS feeds potted roses every fifteen days from midspring to late summer¹, and lists roses among hungry plants fed from April to late August in its UK calendar⁶. Follow the local active growing season. Each spring, it also adds granular rose fertilizer to the surface⁴.

Two rules apply everywhere:

1. Use the label rate, never more³. Extra fertilizer does not feed better; it burns roots.
2. Start with moist soil. Washington State University recommends applying to moist soil, then watering, and never feeding a plant stressed by heat or drought⁷.

Pot profond, terreau, surfaçage tous les deux ans : growing roses in pots demande un suivi plus serré qu'au jardin.

Natural and homemade fertilizers: what the sources say

Compost and well-rotted manure remain the main natural fertilizers recommended for roses here. The SFR spreads compost with the late-winter feed²; the RHS mulches the base with rotted manure¹. Homemade recipes need a separate assessment for each ingredient.

Homemade fertilizer	Assessment
Comfrey liquid	Often rich in potassium, especially when grown on clay soil; the source recipe dilutes 1 part in 20 parts water, applied at the base8
Wood ash	Some potassium, but it raises soil pH: the source limits sifted ash to 100 g per 10 liters of plant liquid (3.5 oz per 2.6 US gal)8
Coffee grounds	Only 1 to 2% nitrogen, with nearly neutral pH: put in compost at no more than 20% of its volume9
Poultry manure	High in nitrogen: use small amounts or leaves develop at the expense of flowers5

The source gives precautions for homemade plant liquidLiquid made by soaking leaves or allowing them to decompose, then diluting it in a watering can.: never spray it on leaves, to avoid inhaling its microbes; wear gloves when handling it and use it within three months⁸. It describes this liquid as weaker than commercial fertilizer and calls for frequent, generous applications⁸. These are source recipes, not established guarantees of safety or effectiveness.

Too much or too little fertilizer: the signs

A very green rose with few flowers has often received too much nitrogen, especially from poultry manure or ammonium sulfate⁵. Excess also produces tender shoots that powdery mildew readily attacks¹⁰.

Excess fertilizer burns. Leaf tips and edges turn brown, young shoots may die, and pots may develop a whitish or brownish crust on the mix or rim⁷. For pots, the remedy given is thorough watering to flush salts out through drainage holes⁷. See excess salts and flushing salts from potting mix.

Deficiency shows on older leaves. General yellowing starting at the bottom points to low nitrogen; yellow young leaves with green veins point to low iron¹¹. See nitrogen deficiency.

Avant d'accuser l'engrais, vérifiez le sol et l'arrosage : yellow rose leaves ont souvent une autre cause qu'une carence.

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Frequently asked questions

When should I fertilize roses?

In the garden, before spring flowering and again in midsummer after the first flush: the RHS gives March or April for the first feed in its UK calendar¹; the SFR gives late June or early July for the second in France². Follow local growth and flowering elsewhere. In pots, feed every fifteen days from midspring to late summer during active growth¹.

Which fertilizer helps roses flower?

A high-potassium fertilizer; potassium supports flowering³. In pots, the RHS switches to tomato feed when buds form¹. Avoid excessive nitrogen, which produces leaves at the expense of flowers⁵.

When should I avoid fertilizing a rose?

During winter dormancy, and after August for pots in the RHS's UK calendar: late feeding produces tender growth damaged by cold⁴. Match that cutoff to local growth and approaching cold. Never feed a dry root ball or a heat-stressed rose⁷.

Are coffee grounds good fertilizer for roses?

They are a weak fertilizer: only 1 to 2% nitrogen, and they do not acidify soil, with a pH around 6.5 to 6.8. Add them to compost at no more than 20% of its volume⁹.

Can I give roses comfrey liquid?

The source allows it at the base: comfrey is often high in potassium, especially when grown in clay soil. The RHS recipe dilutes 1 part liquid in 20 parts water and prohibits spraying it on leaves⁸. This preserves the source recipe without treating its safety or effectiveness as proven.