Houseplants live in a small volume of potting mix, and that mix runs out of nutrients within weeks of repotting. Unlike garden plants, they cannot send roots out to find more food, so they depend entirely on you to replace what they use. Fertilizing houseplants is therefore a regular, gentle routine — little and often, at the right time of year, with the right fertiliser for the plant. It is also one of the easiest routines to get wrong: over-fertilising is far more common and far more damaging than under-fertilising, and the symptoms of too much feed look confusingly like the symptoms of too little.
The good news is that most houseplants need less feeding than their owners think. A plant in fresh potting mix needs no fertiliser for the first six to eight weeks, a plant in winter needs little or none, and a plant that is not growing does not need feeding at all. This guide explains when to feed, what to feed with, how much to use, and how to recognise and fix the mistakes.
When to fertilize houseplants
Feed houseplants during the growing season, roughly from spring to early autumn, when they are actively producing new leaves. In most homes that means March to September in the northern hemisphere, with the heaviest feeding in late spring and summer when growth is fastest. Reduce feeding in autumn as growth slows, and stop feeding almost entirely in winter, when short days and cool rooms mean most plants barely grow. A plant that is fed in winter often shows burnt leaf tips and salt build-up in the mix, because it cannot use the nutrients you are giving it.
Feed only plants that are growing. A plant that has just been repotted needs no feed for six to eight weeks, because fresh mix contains nutrients. A sick, wilting or pest-damaged plant should not be fed until it recovers — fertiliser does not cure a sick plant, and it can make the problem worse by burning stressed roots. A dormant plant such as a cactus in winter needs no feed at all. And a plant that has not been watered properly should be watered first and fed later: fertiliser applied to dry mix burns roots.
Check the plant before you feed. If it is producing new leaves, it is growing and can be fed. If it has not grown for months, find out why — light, water, temperature or pot size — before reaching for the fertiliser bottle. Our growing guides for individual plants, such as monstera deliciosa and fiddle-leaf fig, cover the light and water needs that matter more than feeding.
Which fertiliser to use
A balanced liquid fertiliser — roughly equal nitrogen, phosphorus and potassium, such as a 10-10-10 or 20-20-20 — suits most foliage houseplants. It is easy to dilute, easy to apply, and hard to get badly wrong if you follow the label. Specialist fertilisers suit particular plants: a high-nitrogen feed for leafy plants, a high-phosphorus or high-potassium feed for flowering plants such as African violets and orchids, and a low-nitrogen feed for cacti and succulents. Slow-release granules mixed into the mix at repotting time feed for months and suit gardeners who forget to feed, but they are harder to control — you cannot stop them feeding in winter, and they can build up salts over time.
Organic options work well indoors too. Diluted fish emulsion, seaweed extract and compost tea all feed gently and add biology to the mix, though fish emulsion smells for a day or two and is best used when windows can be opened. Worm castings, applied as a thin top-dressing, feed slowly and rarely burn plants — see our vermicompost guide. Whichever you choose, use half the label rate for most houseplants at first: indoor plants grow slowly, pots are small, and a weak feed given regularly is safer than a strong feed given rarely.
How often and how much
| Plant type | Feeding frequency in growing season | Strength |
|---|---|---|
| Fast-growing foliage (monstera, pothos) | Every 2–4 weeks | Half label rate |
| Slow-growing foliage (snake plant types, ZZ) | Every 6–8 weeks | Half label rate |
| Flowering houseplants | Every 2 weeks while flowering | Half to full label rate |
| Cacti and succulents | Every 6–8 weeks in summer only | Quarter to half label rate |
| Ferns | Every 4 weeks | Quarter to half label rate |
| Orchids | Every 2 weeks in growth, weakly weekly | Quarter label rate |
| Seedlings and cuttings | Only after true leaves, half-strength | Half label rate |
Always water the plant first, then apply fertiliser to moist mix — never to dry mix. Dilute the fertiliser in water according to the label, and apply until a little runs from the drainage hole, which also flushes out excess salts. Once every few months, water the plant thoroughly with plain water and let it drain freely, to wash out the salts that build up from fertiliser. If white crust appears on the surface of the mix or around the drainage hole, that is salt build-up, and the plant needs a good flush with plain water and a pause in feeding.
Signs of over- and under-fertilising
Over-fertilising is the more common problem, and its signs are brown, burnt leaf tips and edges, leaves that wilt even though the mix is moist, white salt crust on the mix surface, and roots that are brown and damaged when you repot. If you see these signs, stop feeding immediately, flush the pot thoroughly with plain water several times, and remove badly burnt leaves. Do not feed again for at least two months, and resume at half the previous rate. In severe cases, repot into fresh mix, trimming away damaged roots.
Under-fertilising is slower and subtler: pale or yellowing older leaves, slow growth, small new leaves, and a plant that looks hungry despite good light and water. It is easily confused with a lack of light, so check light first — a plant in a dark corner will not grow no matter how much you feed it. If light and water are right and the plant is pale and slow, a gentle feed at half label rate every two to four weeks should green it up within a few weeks. If it does not, the problem may be pH or a specific deficiency, and a repot into fresh mix is often the better fix than more fertiliser. See our potting mix recipe guide for the mix, and check your local extension service if a plant problem persists despite good care.
Common mistakes
The most common mistake is feeding too much, too often, or at full label strength — houseplants need less than the label suggests. The second is feeding in winter, when plants cannot use the nutrients. The third is feeding a dry plant, which burns roots — water first. The fourth is feeding a sick or newly repotted plant. The fifth is using a fertiliser meant for outdoor plants at outdoor rates indoors, which is far too strong for a small pot. The sixth is never flushing the pot, so salts build up over months until the plant fails. And the seventh is expecting fertiliser to fix a plant that is short of light: no amount of feeding compensates for a dark room, and over-feeding a light-starved plant makes it worse.
Safety notes
Wear gloves when handling fertiliser, and wash your hands afterwards. Keep fertiliser bottles away from children and pets, and store them upright in a cool place. Do not mix different fertilisers together unless the labels say it is safe. Fish emulsion and other organic feeds smell, so use them when you can ventilate the room. Wash any fertiliser off leaves promptly, because concentrated feed can scorch foliage. If you are unsure about a product or a rate, check your local extension service for advice.
Frequently asked questions
How often should I fertilize houseplants?
Most foliage houseplants do well fed every two to four weeks in the growing season at half the label rate, and not at all in winter. Slow growers such as cacti and succulents need feeding only every six to eight weeks in summer. Always water first and feed moist mix, never dry mix.
Can I over-fertilize a houseplant?
Yes, easily, and it is the most common houseplant feeding mistake. Signs are brown burnt leaf tips, wilting despite moist mix, and white salt crust on the surface. Stop feeding, flush the pot with plain water, and do not feed again for at least two months.
Should I fertilize houseplants in winter?
Usually no. Most houseplants grow little or not at all in winter, so they cannot use the nutrients, and feeding then causes salt build-up and burnt tips. Resume feeding in spring when new growth appears.
What is the best fertiliser for indoor plants?
A balanced liquid fertiliser at half the label rate suits most foliage plants. Flowering plants benefit from a high-potassium feed while flowering, and cacti and succulents need a weak, low-nitrogen feed in summer only. Organic options such as diluted seaweed or fish emulsion also work well.
Do I need to fertilize a plant I just repotted?
No, not for six to eight weeks. Fresh potting mix contains nutrients, and feeding a newly repotted plant can burn its disturbed roots. Wait until the plant is growing again, then start feeding at half strength.