It is not easy to overwinter house plants and keep them healthy and happy through the darkest and coldest months of the year.
So, when winter is on its way you need to apply some extra house plant care and attention to help your plants survive conditions indoors.
Of course, conditions indoors are a lot better than they are outside. But they are still sub-optimal for your plants. Here is why.
- Half of the plants we grow as house plants come from tropical latitudes, where there is year round warmth, rain and humidity, and daylight for at least 10-12 hours a day.
- The other half of the house plants we grow – think cacti and succulents – come from latitudes where there is still 9 to 10 hours of daylight in winter with warm days, but night time temperatures that drop significantly.
- By contrast, in most places in the world, winters are cold with limited hours of daylight. In mid-winter in Scotland where I live, for example, there is only 6.75 hours of daylight and an average maximum temperature of only 7.5°C.
- As a result, we heat our homes, so that even at night the temperatures do not drop very far below 18 to 20°C (64 to 68°F). The heating therefore creates a very warm and constantly dry atmosphere.
- What is more the sun is low in the sky, so the amount of light entering in the house through the windows is much more limited than in the summer.
All of this means that the plants we love to grow are put under stress in winter because our homes are too warm, too dry, and too dark.
Unsurprisingly, given the hostility of these conditions, house plants react by entering a period dormancy, slowing or even ceasing their growth.
We therefore need to treat our plants quite differently in winter compared with how we treat them the rest of the year. So, here are some key steps you need to follow to overwinter your house plants successfully.
Exactly how to overwinter house plants successfully
To overwinter house plants successfully, you need to adjust to changes in the the plants’ requirements in the critical areas listed below.
1.Adjust the watering schedule
Most house plants need less water in winter, as they enter a dormant or semi-dormant state and their growth slows down. Overwatering can lead to root rot, fungal infections, and pest infestations (like fungus gnats), so it is important to check the soil moisture before watering and avoid soggy soil.
As a general rule of thumb, water your house plants when the top inch of soil feels dry to the touch. But this may vary depending on the type of plant, the size of the pot, and the humidity level in your home. You can also use a moisture meter or a wooden skewer to test the soil moisture more accurately. Therefore, in summary:
- Check soil moisture before watering using your finger or a moisture meter
- Water when the top 1 inch of soil is dry
- Reduce watering frequency compared to summer.
2. Provide as much light as you can
Light affects your plants’ photosynthesis, metabolism, and flowering. In winter, the days are shorter and darker, so you may need to move your plants closer to a bright window or supplement them with artificial light sources such as grow lights or fluorescent bulbs.
Ideally, you should provide your house plants with 12 to 16 hours of light per day. But this is not always possible. You should also factor on the type of plant and its particular light requirements. Some plants prefer bright indirect light, while others can tolerate direct sunlight or low light conditions.
You can also rotate your plants every few weeks to ensure even growth and prevent them from leaning towards the light source. Therefore:
- Move plants closer to bright, south-facing windows as days get shorter
- Supplement natural light with grow lights or fluorescent bulbs
- Provide 12-16 hours of light per day if you can
- Rotate plants every few weeks for even growth.
3. Optimise temperature
House plants prefer consistent warm temperatures between 65-75°F (18 to 24°C) during the day for healthy transpiration and respiration. Cooler 55-65°F (13 to 18°C) temperatures overnight are fine, but avoid any sudden fluctuations that shock plants.
- Daytime temperature between 65-75°F
- Nighttime temperature between 55-65°F
- Avoid placing plants near drafts, vents, heaters etc.
4. Optimise humidity
Most houseplants need 40-60% humidity, but this will depend n the type of plant and its origin. Most tropical plants may need higher humidity levels, while some succulents and cacti may need lower humidity levels.
In winter, central heating in the home creates low humidity which can cause leaves to dry out and brown. Use humidifiers, mist plants frequently or sit them on pebbles in trays filled with water to keep moisture levels optimal.
- Ideal humidity level is 40-60% for most plants
- Use a humidifier, mist plants regularly, place them together in groups, or use pebble trays to create more humid conditions.
- Remember, tropical plants need higher humidity and succulents/cacti need lower humidity.
5. Reduce fertilisation
Most house plants do not need fertilising in winter, as they are not actively growing and their nutrient needs are minimal. Fertilising them too much or too often can cause salt buildup in the soil, leaf burn, or excessive growth that can weaken the plant’s structure and make it more susceptible to pests and diseases
Go light, no more than monthly for most plants. Avoid fertilising completely when the soil is dry or the plant is stressed. So:
- Fertilise sparingly or not at all in winter
- If fertilising, use a diluted balanced fertilizer (10-10-10) no more than once a month
- Avoid fertilising when soil is dry.
Removing dead or diseased foliage in winter limits pest infestations and diseases. Pruning also shapes your plant and encourages new growth in spring. You should use clean and sharp tools to make clean cuts at an angle just above a leaf node or a branch junction. Avoid pruning more than one-third of your plant at a time.
Therefore, if pruning in winter:
- Remove any dead, diseased or damaged parts of plants
- Use clean, sharp tools
- Make cuts at an angle just above a leaf node
- Avoid removing more than 1/3 of plant at one time.
Repotting can help you refresh the soil, provide more space for your plant’s roots, and improve drainage and aeration.
You should generally repot your house plants when they become root-bound (when the roots start growing out of the drainage holes or circling around the pot), when the soil becomes compacted or depleted of nutrients, or when you notice signs of pests or diseases in the soil.
However, unless the plant is particularly stressed, it is best to leave repotting to the end of winter or early spring when the plant is about to enter active growth.
- Repot at the end of winter if plants are root bound or depleted of nutrients. Repot earlier if you see signs of harmful pests or diseases
- Use a pot 2 inches wider than the current pot
- Use fresh, sterile potting mix suitable for the plant
- Water plant thoroughly after repotting.
By following these essential steps, you should be able to overwinter house plants successfully and enjoy their beauty and benefits all year round.
It is always best to check on your plants regularly to check for any signs of stress.
And remember, when the plant is not in active growth it does not need to take up much water or plant food, because it is does not need the energy to build new leaf, stem or root structures. Therefore, the biggest danger to your plants in winter comes from over-watering and over-feeding, so show some restraint!