Winter often brings with it a wave of questions for indoor plant lovers. Among the most common? Whether or not you should fertilise your plants during the cooler months. There’s a long-standing “rule” that plants don’t need fertilising in winter, but this isn't necessarily accurate. The truth is, it’s not so simple. Just like people, plants have unique needs depending on their environment and care routines.

This guide will help you separate myth from reality when it comes to winter plant care and provide practical tips to keep your indoor jungle thriving year-round.

Understanding Plant Dormancy

The idea that all indoor plants go dormant in winter stems from what happens in nature. As daylight hours shorten, temperatures cool, and growth slows, many plants enter a period of rest known as dormancy. However, indoor plants don’t automatically follow this seasonal rhythm. Factors like indoor heating, grow lights, and varying humidity levels can create conditions that mimic growing seasons, even in winter.

But what exactly is dormancy? Dormancy is a state of reduced metabolic activity, where growth slows or stops entirely, allowing the plant to conserve energy. Whether your houseplants enter dormancy depends on:

Light: Less daylight can signal a plant to rest.
Temperature: Cooler indoor temperatures often lead to slower growth.
Species: Not all plants follow the same dormancy rules. Tropical species, for example, may grow year-round if they receive adequate light, warmth and care.

How to Identify Active Growth in Winter

If your plants are still actively growing, winter fertilising can work wonders. But how do you tell if your indoor plants are in need of extra nutrients in the colder months? Look out for these signs:

New Leaves or Shoots: If your plant is producing fresh leaves or shoots, it’s actively growing and not in a dormant phase. This is a great sign that your plant is happy and thriving in its current environment.  

Unfurling Leaves: For plants like monstera, calathea, or other tropical varieties, the appearance of new leaves that slowly unfurl is a clear indicator of activity. This process shows that your plant has the energy and resources it needs to produce beautiful, healthy foliage.  

Healthy Root Expansion: When repotting or inspecting the roots, you might notice vibrant, actively growing roots. These roots are typically white or light-coloured and indicate that the plant is absorbing nutrients and water efficiently, supporting its overall growth.

Plants under grow lights are even more likely to need fertilising over winter, as the consistent light conditions encourage growth.

Choosing the Right Fertiliser for Winter Care

If you’ve determined that your plants are still active, selecting the right fertiliser is key. Here are the main types to consider:

Organic vs. Mineral Fertilisers

Organic fertilisers, like the Plant Runner Soil & Microbe Booster, are ideal for winter use. They release nutrients slowly and enhance soil microbes to support steady growth. Organic options are also gentle, reducing the risk of over-fertilising during slower growth periods.

Mineral fertilisers like our Indoor Plant Food offer precise nutrient delivery, such as high NPK ratios for plants in their growth phase. However, these are best diluted heavily in winter to prevent nutrient burn.

Low NPK Fertilisers

For winter care, opt for a fertiliser with low nitrogen, phosphorus, and potassium (NPK) values. These formulations, such as our Soil and Microbe Booster, ensure plants get essential nutrients without overwhelming them.

Liquid or Slow-Release Fertilisers

Liquid fertilisers like our Indoor Plant Food are fast-acting and easy to control, perfect for active plants like pothos or philodendrons. Dilute to half or quarter strength for winter use.

Slow-release fertilisers, such as our Soil and Microbe Booster are excellent for long-term nourishment but may break down unpredictably due to cooler indoor temperatures.

Adjusting Your Fertilising Habits

Even if your plants are active, a few tweaks to your routine are critical to avoid over-fertilising during winter. 

Dilution is Key

Reduce the concentration of your fertiliser by diluting it to half or quarter strength. This ensures that your plants receive a gentle supply of nutrients that won’t overwhelm their slower metabolic processes.

Cut Back on Frequency

Instead of fertilising weekly or bi-weekly, try fertilising every 4–6 weeks. Less frequent applications align with your plant’s potentially reduced nutrient demands.

Observe and Adapt

Always keep an eye on your plants after fertilising. Watch for signs of over-fertilisation, such as browning leaf tips or wilting, and adjust accordingly.

Alternative Ways to Support Winter Plant Health

Fertilising isn’t the only way to care for your plants during winter. Consider these alternative strategies to maintain their health:

Boost Humidity

Most indoor plants, especially tropical varieties, suffer from dry indoor air in winter. Increase humidity using:
A humidifier.
A pebble tray with water under your plant pots.
Grouping plants together to create a microclimate.

Improve Lighting

Shorter days mean less light for your plants. Move them closer to windows, but avoid direct drafts or icy windowsills. Using grow lights can also make a dramatic difference during the darker months.

Clean Your Leaves

Dust accumulates on leaves, blocking light and reducing photosynthesis. Use some Neem Oil and a damp cloth to gently wipe them down every few weeks, or give your plants a light shower.

Routine Check-Ups

Inspect your plants for pests, such as spider mites, which thrive in winter’s dry conditions. Neem oil or a gentle insecticidal soap can help combat infestations. 

Recommendations for Sustainable Plant Care

If sustainability is a priority for you, think about using organic products that nurture plants and the planet. Their Soil & Microbe Booster is carbon negative, combines Frass and Biochar, and is an eco-friendly solution with incredible plant benefits:

Frass: A natural byproduct of insect farming, frass is rich in chitin, a compound that boosts plants’ natural defenses against pests and diseases. It also enhances microbial activity in the soil, promoting a healthier and more balanced growing environment.

Biochar: Derived from organic materials, biochar improves soil structure by increasing moisture retention, preventing water loss, and regulating soil conditions. It creates an ideal environment for stronger, healthier root systems to thrive, while also supporting beneficial soil microbes.

These sustainable solutions not only help your plants thrive but also contribute to a healthier planet.

Winter Plant Care is About Balance

The myth of “no fertilising in winter” isn’t a one-size-fits-all rule. By assessing your plant’s growth patterns, tweaking your fertilising habits, and incorporating sustainable practices, you can help your indoor plants thrive year-round—even in the colder months.
Want to take the guesswork out of plant care? Explore Plant Runner Indoor Plant Food and the eco-friendly Soil & Microbe Booster to give your green companions the attention they deserve, in any season.