houseplant care
Houseplant fertilizer schedule — month-by-month NPK guide
When to feed houseplants by season, how to read NPK, why newly-bought plants need no fertilizer for 6 weeks, and how to flush salt build-up.
Houseplant fertilizer schedule — month-by-month NPK guide
Houseplant fertilizing sits in the gap between "no one tells you, so you skip it for a year" and "online advice says feed weekly and the plant dies of salt burn." Neither is right. Indoor plants in pots have one cubic foot of soil to draw from for years — without supplemental nutrients they slowly run out of nitrogen, phosphorus, and potassium and stop growing. But they also can't escape excess feed, so over-fertilizing burns roots faster than dehydration does. This guide is the realistic schedule: when to feed, what NPK ratio actually matters for which plant, which brands work in the US and UK, and the salt-flush protocol that prevents 80% of fertilizer accidents. For the chemistry vocabulary, see NPK.
Try Growli: Add your plants to Growli. The app tracks each plant's last feeding date and tells you which ones are due this week based on season, species, and how long ago you bought the plant from the nursery.
NPK basics in 90 seconds
Every fertilizer label has three numbers, e.g. 10-5-5 or 20-20-20. They are the percentage by weight of:
- N — Nitrogen. Drives leaf and stem growth. Houseplants with green showy foliage (monstera, pothos, philodendron, snake plant) want N-leaning feed.
- P — Phosphorus. Drives root development and flowering. Flowering houseplants (peace lily, orchid, anthurium, African violet) benefit from a P boost during bud formation.
- K — Potassium. Drives overall vigour, disease resistance, and water regulation. All plants need it; deficiency shows as yellowing leaf edges.
Balanced ratios (10-10-10, 20-20-20) work for almost every common houseplant. Specialty ratios matter mostly for: orchids (10-30-20 during bud set), cacti (low-N, around 2-7-7), and African violets (matched even ratios with extra micronutrients). Full glossary entry at NPK; see also types of fertilizer for the broader categorisation (synthetic vs organic, liquid vs granular, slow-release vs instant).
The month-by-month schedule
Default for foliage houseplants in temperate climates (US most of the country, all of the UK):
| Month | Action | Why |
|---|---|---|
| January | Skip | Lowest light, plants dormant |
| February | Skip | Still dormant; new growth not yet active |
| March | Resume — half-strength balanced | First feed of the season as light returns |
| April | Half-strength balanced | Active growth begins |
| May | Half-strength balanced | Peak growing month |
| June | Half-strength balanced | Peak growing month |
| July | Half-strength balanced | Peak growing month |
| August | Half-strength balanced | Late season feeding |
| September | Half-strength balanced (final feed) | Winding down |
| October | Skip | Reduce as light drops |
| November | Skip | Plants semi-dormant |
| December | Skip | Plants dormant |
Key rules:
- Half-strength always. Manufacturer labels are written for outdoor garden plants in full sun. Indoor plants need roughly half what the label says, full stop. If the label says 1 tsp per gallon, use 1/2 tsp.
- No feed on dry soil. Always water first or feed with the watering — fertilizer salts on dry roots cause chemical burn. The 30-minute rule: water 30 minutes before feeding, or mix the fertilizer into the watering can directly.
- No feed for 6 weeks after buying. Nurseries pre-load growing media with slow-release fertilizer (Osmocote or equivalent). Adding more liquid feed in the first 6 weeks pushes you into burn territory before the slow-release runs out.
- No feed for 4-6 weeks after repotting. Fresh potting mix already contains starter charge. Wait until that's depleted.
- No feed if the plant is sick. Fertilizer is not medicine. A wilting, root-rotted, or pest-infested plant needs the root cause fixed first; feeding stressed plants kills them faster.
For species that flower indoors (orchid, peace lily, anthurium), switch to a "bloom booster" (higher P, e.g. 10-30-20) for 2-3 feedings during bud formation, then return to balanced. For cacti and succulents, feed only April-September at quarter-strength using a low-nitrogen cactus formula.
Fertilizer brands — US and UK
Brand names matter because they're what readers buy. All brands below verified available in 2026 via WebSearch.
US brands
- Miracle-Gro All Purpose Plant Food (24-8-16) — synthetic, blue water-soluble crystals, sold everywhere (Home Depot, Lowes, Walmart, Amazon). The default for casual houseplant owners. Use at half-strength.
- Miracle-Gro Indoor Plant Food (1-1-1) — much gentler liquid specifically for houseplants. Good for nervous new gardeners — harder to over-feed.
- Espoma Indoor! liquid (2-2-2) — organic, derived from kelp and fish meal. Slower-acting than synthetics, gentler, slight fish smell when fresh.
- Dr. Earth Pump & Grow Indoor Plant Food (1-1-1) — organic liquid, OMRI listed, very low burn risk. Higher price point but forgiving.
- Osmocote Plus Indoor & Outdoor Smart-Release — slow-release pellets that feed for 6 months. Sprinkle in spring, forget about it. Good for travellers.
UK brands
- Westland Houseplant Feed — liquid concentrate, widely sold at B&Q, Wickes, Homebase, garden centres. Reliable mid-range default.
- Phostrogen All-Purpose Plant Food — soluble powder, around 14-10-27, sold by Bayer in UK and EU markets. Has been on UK shelves for 60+ years and remains widely stocked.
- Levington Tomorite Concentrated Tomato Food — primarily for tomatoes (high K, 4-3-8), but RHS notes it works well for flowering houseplants when bud formation is the goal. Don't use on foliage-only species.
- Baby Bio Original — liquid, around 10.6-4.4-1.7, the iconic UK houseplant feed. Small bottle lasts a year. Tradition more than science but it works.
- Doff All Purpose Soluble Plant Feed — budget option, widely available at garden centres and supermarkets.
The brand matters less than the routine — any balanced fertilizer used consistently at half-strength outperforms any premium product used erratically.
Plant-specific patterns
Rough groupings, by demand level:
Heavy feeders — monthly during growing season
- Monstera deliciosa, pothos, philodendron (vining and self-heading), tradescantia, fiddle leaf fig, rubber plant, schefflera, croton
- See monstera care, pothos care, and fiddle leaf fig care
Moderate feeders — every 6-8 weeks during growing season
- Calathea, peace lily, spider plant, dracaena, aglaonema, ZZ plant, prayer plant
- See calathea care, peace lily care, zz plant care
Light feeders — every 8-12 weeks, quarter-strength
- Snake plant, cast iron plant, jade plant, aloe, most succulents, most cacti
- See snake plant care, aloe vera care, jade plant care
Specialty feeders — bloom booster during bud set
- Orchid (Phalaenopsis especially), anthurium, African violet, hoya
- Switch to high-P feed (10-30-20) for 2-3 feedings as buds appear
- See orchid care
For the broader best-fertilizer roundup, see best fertilizer for indoor plants.
Salt build-up and the flush protocol
Every liquid fertilizer leaves mineral salts in the soil. Over months, these accumulate and damage roots — the visible symptom is a white or yellow crust on the soil surface or around the pot rim, plus increasing crispy leaf tips even though humidity and watering are correct.
Flush twice a year (March and August):
- Move the pot to a sink, bath, or outdoors.
- Run room-temperature water slowly through the pot. Let it drain.
- Repeat 3-4 times. You're aiming for water roughly 3-4x the pot volume passing through.
- Let drain completely. Empty any standing water in the saucer.
- Skip the next scheduled fertilizing — the soil is depleted, give it 2 weeks to recover.
If the soil surface has visible white salt crust, scrape off the top 1 cm and replace with fresh potting mix before flushing.
For severe build-up (the plant has been over-fertilized for a year), repot completely into fresh mix — see how to repot a plant and use our pot size calculator to confirm the new pot size.
Organic vs synthetic — when it matters
For indoor pots, the differences are smaller than gardening media imply:
- Synthetic (Miracle-Gro, Phostrogen, Baby Bio) — fast-acting, predictable NPK ratios, cheap, easy to over-apply. Best for new growers who follow a schedule.
- Organic (Espoma, Dr. Earth, fish emulsion, worm castings) — slower-acting, builds soil microbiome over time, gentler — harder to burn plants even at recommended strength. Slight smell on fresh application (fish emulsion especially).
Most indoor plants do fine with either. If you compost or care about soil microbiology, organic is the better fit. If you want clear numbers and consistent results, synthetic is fine. Switching between them is also fine — plants don't care about your worldview.
Common fertilizing mistakes
- Feeding in winter. Plants are dormant. Excess feed in low-light winter conditions accumulates as salt because the plant can't use it. Pause November-February in all climates that experience winter darkness.
- Feeding at full label strength. Labels are written for outdoor garden plants. Indoor plants need half. Quarter for cacti and succulents.
- Feeding newly bought plants immediately. Nursery growing media is pre-loaded. Wait 6 weeks.
- Feeding on dry soil. Burns roots. Always water first, or mix into the watering can.
- Feeding a stressed plant. A plant with root rot, pest infestation, or transplant shock cannot use the nutrients and they accumulate as salt. Fix the underlying issue first — see why is my plant dying.
- Skipping the flush. Two years of monthly liquid feed without a flush guarantees salt damage. Twice a year takes 10 minutes per plant.
Related
- Best fertilizer for indoor plants — brand-by-brand comparison
- Types of fertilizer — synthetic vs organic, liquid vs granular
- Indoor plant care — the broader care hub
- How to repot a plant — when fertilizing isn't enough
- Pot size calculator — match the pot to the plant
- Brown spots on plant leaves — diagnose over-fertilizing
- Yellow plant leaves — diagnose nutrient deficiency
- Humidity for houseplants — companion seasonal care guide
NPK guidance cross-referenced with RHS Fertilisers: Types and Uses and US Extension service publications. Brand availability verified May 2026.
Frequently asked questions
How often should I fertilize my houseplants?
Monthly with a balanced liquid fertilizer at half the label strength, from March through September. Pause completely October through February — plants are dormant or semi-dormant in low winter light and cannot use the nutrients, which then accumulate as salt and damage roots. Cacti and succulents need even less — every 8-12 weeks at quarter strength during the growing season only.
What NPK ratio is best for houseplants?
For most foliage houseplants (pothos, monstera, philodendron, snake plant, ZZ, peace lily, calathea), a balanced ratio like 10-10-10 or 20-20-20 works perfectly. For flowering plants entering bud set (orchid, anthurium, African violet), switch to a higher-phosphorus 'bloom booster' formula like 10-30-20 for 2-3 feedings, then return to balanced. Cacti and succulents prefer low-nitrogen ratios like 2-7-7.
Why shouldn't I fertilize a newly-bought houseplant?
Nurseries pre-load growing media with slow-release fertilizer pellets (Osmocote or equivalent) that feed the plant for roughly 6 weeks after purchase. Adding liquid feed during this period pushes you into chemical-burn territory before the slow-release runs out — the visible symptom is crispy brown leaf tips within a month of buying. Wait 6 weeks before the first liquid feed.
What does over-fertilizing look like?
A white or yellow salt crust on the soil surface and around the pot rim, increasing crispy brown leaf tips even when humidity and watering are correct, sudden leaf drop in younger leaves, and yellowing combined with stunted new growth. The fix is a flush: run room-temperature water through the pot 3-4 times until it streams clear from the drainage hole, then skip the next scheduled feeding.
Which fertilizer brands work best in the US and UK?
US: Miracle-Gro Indoor Plant Food (1-1-1) for casual use, Espoma Indoor liquid (2-2-2) for organic, Dr. Earth Pump & Grow for low burn risk, Osmocote Plus pellets for set-and-forget. UK: Westland Houseplant Feed, Baby Bio Original, Phostrogen All-Purpose Plant Food, Levington Tomorite for flowering plants. All verified available at major garden centres and online retailers in 2026. Brand matters less than consistency — any balanced fertilizer at half-strength on schedule outperforms premium product used erratically.
Should I use organic or synthetic fertilizer?
For indoor pots, the practical difference is smaller than gardening media imply. Synthetic (Miracle-Gro, Phostrogen, Baby Bio) is fast-acting, cheap, predictable, and easier to over-apply. Organic (Espoma, Dr. Earth, fish emulsion, worm castings) is slower-acting, builds soil microbiome over time, and is much harder to burn plants with. If you compost or care about soil biology, choose organic. If you want clear numbers and consistent results, synthetic is fine. Plants tolerate switching between them.
How do I flush salt build-up from houseplant soil?
Move the pot to a sink, bath, or outdoors. Run room-temperature water slowly through the pot, letting it drain completely. Repeat 3-4 times — you're aiming for water roughly 3-4x the pot volume passing through. Let the pot drain fully and empty any standing water in the saucer. Skip the next scheduled feeding. Do this twice a year (March and August) for any plant on a regular fertilizing routine.
How does Growli handle fertilizing reminders?
Add your plants to Growli and the app tracks last-fed date per plant. The morning briefing tells you which plants are due based on species (heavy feeder vs light feeder), season (auto-pauses October-February), and time since purchase (auto-skips first 6 weeks for nursery plants). The conversational AI also troubleshoots over-fertilizing — upload a photo of a salt-crusted pot and it walks you through the flush protocol step by step.