Temperature and humidity guide for houseplants

Whether you're just starting to keep and grow plants indoors or you already have an urban jungle, there are a few things you need to know about temperature and humidity. Both of these are important for your houseplant's health and growth. They're often overlooked, and that can cause your plants to struggle.

Find out how to keep your home's temperature and humidity at the perfect levels to create the perfect growing environment for your adorable houseplants.

The ideal temperature for houseplants

It is important to remember that every plant has a preferred temperature range, often based on its natural habitat. Photosynthesis only takes place optimally at the right temperature. Whenever the temperature is too high or too low, this vital process slows down, and so does the plant's overall health.

Therefore, finding the right temperature is very important. But what temperature is needed for what? The average home temperature ranges from 18-28°C, usually suitable for most houseplants. It becomes more challenging when the room gets colder or hot in summer.

Expert tip! If you're not sure what temperature your houseplant needs or tolerates, you can always look it up in care guides or just think about what temperatures it gets in its natural habitat.

The most important thing is to make sure that the temperature in your space does not fluctuate too much. So, make sure that the temperature difference between day and night is as small as possible. If the difference between day and night is too big or the nights are too cold, it will take too long for the plant to recover. There is also a greater chance of mildew developing.

Signs of temperature stress

Stress from too high a temperature is especially common in plants placed directly in hot sunlight, like in a south-facing window or near heating vents or radiators. If you suspect heat stress, look for signs like these:

1. The leaves turn brown, show dry spots, or appear dry and burnt
2. Plant start to wilt from excessive evaporation
3. Plants may grow slower, and their leaves may be smaller
4. Leaves start to curl or even drop off

Plants placed in cold rooms or touching cold windows during winter are especially vulnerable to cold stress. Typically, you'll see these symptoms:

1. Leaves and plants start to wilt from cold damage
2. Leaves and stems turn brown, black
3. The browned or blackened parts of the plant become soft or even mushy
4. Plant growth slows down or enters a dormancy period

How to keep the temperature right for your houseplants?

In case you are having trouble getting the right temperature for your houseplants, here are a few tips that might help you:

1. Use a (mini)greenhouse. A greenhouse is an option to maintain the temperature around your plant(s).
2. Beware of draughts. In the winter, you have to watch out for draughts, breezes and gusts of wind. To prevent your plants from falling victim to sudden temperature changes, place them away from vents, windows, doors or other places where air can enter from outside.
3. Beware of overheating. It is normal to want to protect your plants from the cold by turning up the thermostat, but too much heat can be just as big a threat to them.
4. Group your plants together. If you put your plants together in groups, the air and moisture are trapped between each of them. In this way, they also keep each other a little warmer.

The ideal air humidity for houseplants

One of the biggest problems in keeping plants indoors is spending weeks or months in a room with central heating or another artificial heating method. The good news is that we can prevent and treat humidity problems by knowing the needs of the plants and improving the humidity in our room.

The measurement of humidity is the so-called relative humidity, where water vapour is measured in relation to the number of water particles that can be found in a certain amount of air. So, what is the best humidity level for plants? An ideal humidity level for most adult plants is 60% to 70%. Some tropical plants are used to humidity levels of up to 90%. Many succulents, such as cacti, only need 10% humidity. As a general rule, plants with thicker leaves can tolerate lower humidity levels.

Different humidity levels:

• Low humidity (10-40%): This range suits plants that thrive in arid conditions. The air usually becomes thus dry when heating is used. Cacti and succulents will do well, but most plants will have leaf problems.
• Moderate humidity (40-60%): Most common houseplants thrive in this range. Most homes have this level of humidity in the summer. Some plants still need some help, then you can mist them or place a water tray nearby.
• High humidity (60-80%): This is ideal for almost all tropical indoor plants. However, it is difficult to maintain indoors. You can maintain this level with an enclosed terrarium or small greenhouse.
• Very high humidity (80-90%): Few houseplants will need humidity this high, but it could suit some very specific tropical plants like certain orchids and carnivorous plants. For humans, however, it is not healthy at all! Only greenhouses or enclosed environments can achieve this level of humidity.

Signs of humidity stress

Stress from too low humidity is especially common during heating periods (near radiators and hearing vents), dry climates, or air-conditioned spaces. You can look for signs like this:

1. The edges or tips of the leaves turn brown
2. Leaf edges turn yellow
3. Leaves dry out and shrivel up/curl up

Stress from high humidity often occurs in greenhouses, terrariums, bathrooms, kitchens, or tropical climates. You can look for signs like:

1. Fungus/Mildew on the leaves
2. Fungus/Mildew on the potting soil
3. Leaves and stems start showing signs of rot

How to keep humidity levels right for your houseplants?

In case you are having difficulty getting the proper humidity levels for your houseplants, we have listed a few tips that might be of help to you:

1. Misting. Simply mist lukewarm water on the leaves with a spray bottle. Just remember you’ll have to mist frequently as this effect is temporary.
2. Group your plants. If you put plants together in groups, the air and moisture are trapped between each of them. They can also use each other's moisture from the soil. If you do this, you have to leave some (growing) space between the plants.
3. Tray with pebbles or hydro grains. The tray consists of small pebbles or hydro grains covered with water. The water should be just below the top of the pebbles so the plant does not suck up water and remains well-aerated.
4. Humidifier. A humidifier is a device that adds humidity to the air through evaporation. It's probably the easiest way to raise the humidity in your room.
5. Hang your clothes out to dry. You can also simply hang your clothes out to dry in the house (near your plants) after washing them. This increases the humidity in the air as the water evaporates from the clothes.
6. Use a (mini)greenhouse. A greenhouse is another option to maintain a higher humidity level for your plants. If you have tropical plants, low humidity can kill your plants.

How to measure temperature and humidity in your home?

We can measure temperatures with a thermometer, and we can measure humidity with a hygrometer, which measures the amount of moisture in our room air. Many thermometers already come with a hygrometer, or vice versa. Therefore, it would make sense to acquire a device that measures both. If needed, you can move it from one place to another.