Indoor Plants: How to Keep Your Houseplants Thriving Year-Round

Indoor plants bring life, texture, and calm to any space—but behind every healthy monstera, pothos, fiddle leaf fig or peace lily is a steady diet of the right fertiliser. While outdoor soil contains natural nutrients and organic cycles, indoor plants rely entirely on what you give them. Over time, even the best potting mix runs out of essential nutrients, making regular fertilising a must for vibrant leaves, strong roots, and continued growth.

Why Indoor Plants Need Specialised Fertiliser

Indoor conditions are very different to what plants experience outdoors. With limited light, restricted root space, and fixed potting media, most houseplants grow slower—but are more vulnerable to nutrient deficiencies. Overwatering, low humidity, and poor drainage can further reduce nutrient uptake, even when fertiliser is present.

Fertilising indoor plants is not about speed—it’s about balance. Too little, and growth stalls. Too much, and root burn or salt build-up can damage the plant.

Key nutrient needs for houseplants:

Nitrogen (N): Encourages lush, green foliage. Ideal for leaf-heavy plants like pothos, ferns, and philodendron.
Phosphorus (P): Supports root strength and flower production—critical for orchids, anthuriums, and flowering indoor plants.
Potassium (K): Aids overall plant health, disease resistance, water regulation, and cell strength.
Micronutrients: Magnesium, iron, manganese, and boron help prevent yellowing leaves, boost chlorophyll, and support metabolism.

Indoor plants also benefit from fertilisers that are:

pH-balanced: Prevents nutrient lockout and supports uptake in neutral to slightly acidic mixes
Chloride- and urea-free: Reduces leaf burn risk, especially in tropical species
Low-salt formulations: Safe for consistent use in closed potting systems

Even so-called “slow growers” need nutrition. If your indoor plant is putting out new growth, developing roots, or flowering—it’s using nutrients.

273495685_457991439140604_8161187767324530912_n

298359956_377924877839870_5716181156787135030_n

How to Grow Healthy Indoor Plants – Feeding, Lighting, Soil, and Humidity Tips

Fertilisers work best when paired with the right environmental care. Many fertiliser issues—like stunted growth or yellowing—aren’t always from a bad product, but from poor conditions that prevent absorption. Here’s how to give your indoor plants the best chance at success.

Choose the Right Light

Most common houseplants (like peace lilies, calatheas, and snake plants) prefer bright, **indirect light**. Positioning them near east- or north-facing windows works well. Fiddle leaf figs, hoyas, and bird of paradise need stronger light and may benefit from filtered sun or grow lights. Insufficient light slows growth and nutrient demand—but adding fertiliser won’t help if the light is wrong.

Water Correctly for Fertiliser Uptake

Improper watering is one of the biggest reasons fertiliser fails. Roots absorb nutrients best in **moist—but not soggy—conditions**. Overwatering can suffocate roots, while underwatering reduces absorption.

Water thoroughly until excess drains from the pot
Allow the top 2–4 cm of soil to dry before re-watering
Reduce watering in winter but don’t let roots dry out completely

Soil & Drainage Matters

Most indoor plants do best in **free-draining, peat-free mixes** with good aeration. Adding perlite or coconut coir improves drainage and helps prevent root rot, especially when using liquid fertiliser. Avoid compacted or reused soil that restricts nutrient flow. If a plant has been in the same pot for 2+ years, consider repotting or top-dressing.

Humidity & Temperature

Low humidity and dry air (especially from heaters or air conditioning) can stress indoor plants, making them more prone to nutrient deficiencies. Mist regularly, use pebble trays, or place plants in higher humidity zones like bathrooms or kitchens. Temperature also plays a role. Cold air slows down root activity and nutrient absorption, so reduce feeding in winter unless your space stays warm year-round.

263600340_928711314731685_2281533017927927443_n

What Is the Best Fertiliser for Indoor Plants?

The best fertiliser for indoor plants is one that delivers a **complete NPK balance**, includes micronutrients, and is suitable for use in controlled pot environments. At CompleteGrow, we recommend only **liquid, pH-buffered, chemical fertilisers** designed to be gentle on roots but powerful in results.

What NPK Ratio Do Indoor Plants Need?

A general NPK ratio of **20-20-20** is ideal for all-purpose feeding across foliage and flowering houseplants. It provides even support for:

Leafy greens like monstera, pothos, calatheas, ferns, and ZZ plants
Flowering indoor plants like orchids, anthuriums, and peace lilies
Slow-growing succulents and snake plants with occasional low-strength feeds

For flowering phases, a **high-potassium formula like 4-18-38** may be used to boost bloom production and enhance flower colour and longevity. Micronutrients like **magnesium, boron, and iron** are especially important in indoor setups, where deficiencies can quickly show as pale leaves, edge burn, or stalled growth.

Feeding Schedule for Indoor Plants

Spring: Resume feeding every 10–14 days as new growth appears
Summer: Feed consistently—weekly or fortnightly depending on plant type and light levels
Autumn: Taper down to monthly feeds unless under grow lights
Winter: Pause or feed once every 4–6 weeks if in warm, well-lit environments

Always dilute liquid fertiliser to the recommended level (often 4 mL per litre). For sensitive plants like ferns or calatheas, consider starting with a half-strength mix and adjusting based on response.

Signs Your Indoor Plant Needs Fertiliser

Pale, yellowing leaves with green veins (possible magnesium or iron deficiency)
Slow or no new growth despite good light and water
Smaller, duller leaves than normal
Failure to flower in normally blooming varieties

By using the right indoor-specific fertiliser, you support long-term root health, lush growth, and a strong resistance to pests and disease—without overloading your plant or damaging the soil.