Indoor plants and ornamentals generally require a certain level of humidity, as they absorb water not only from the soil but also from the air through their leaves. Humidity levels that are too low for indoor plants can cause the plant to dehydrate quickly, dry out its leaves or stop growing. Conversely, humidity levels that are too high can cause waterlogging, mold or leaf disease.
Too low humidity can cause plants to lose water quickly, dry out their leaves, or stop growing.
What is humidity?
Humidity for indoor plants is the level steam in the air in the growing environment, affecting the growth, health and water absorption capacity of the plant.
How to measure air humidity?
We can measure humidity with a hygrometer to know how much moisture is in the air. Many thermometers come with a hygrometer or vice versa. So it makes sense to buy a device that can measure both. You can move it from place to place if needed.
Ideal air humidity for indoor plants
The ideal humidity for most mature plants is 60 to 70 degrees Fahrenheit. Some tropical plants are accustomed to humidity levels as high as 90 to 100 degrees Fahrenheit. Many succulents, such as cacti, only need humidity levels of 10 to 10 degrees Fahrenheit. As a general rule, plants with thicker leaves can tolerate lower humidity.
The ideal humidity for most mature plants is 60% to 70%.
Humidity levels for plants
Low humidity (10-40%)
This range is suitable for plants that thrive in arid conditions. Cacti and succulents will do well, but most other plants will have leaf problems.
Moderate humidity (40-60%)
Most common houseplants thrive in this range. Most indoor environments have this humidity level, but it varies by season. Some plants need more humidity, so mist them with water or place a tray of water nearby.
High humidity (60-80%)
This humidity ideal for most tropical houseplants. However, it is difficult to maintain this humidity indoors. You can maintain this level with an enclosed terrarium or small greenhouse.
Very high humidity (80-90%)
Very few houseplants need such high humidity, some tropical plants like some orchids, anthuriums, begonias and carnivorous plants need very high humidity. However, for humans, it is not healthy at all! Only greenhouses or closed environments can achieve this level of humidity.
Signs of plant problems due to humidity
Stress due to humidity too low is the most common case when growing plants indoors. You may see the following signs:
- Leaf edges or tips turn brown
- The edges of the leaves turn yellow.
- Leaves dry and curled
Stress due to high humidity Commonly occurs in greenhouses, terrariums, bathrooms or tropical climates. You can look for signs such as:
- Fungus/mold on leaves
- Fungus/mold on potting soil
- Leaves and stems begin to show signs of rot.
How to keep the humidity right for indoor plants?
In case you are having trouble getting the humidity right for your houseplants, here are some tips that might help you:
1. Mist
Simply mist the leaves with warm water using a spray bottle. Just remember that you will need to mist regularly as the effect is only temporary.
2. Group your plants
If you group plants together, air and moisture will be trapped between each group. They can also use each other's moisture from the soil. If you do this, you must leave some space between the plants to let them 'breathe'.
3. Tray for gravel or water
A tray of small pebbles or a water tray can also increase humidity. The water should be just below the surface of the pebbles so the plants don't absorb it and it stays well ventilated.
4. Humidifier
A humidifier is a device that adds moisture to the air through evaporation. This is probably the easiest way to increase the humidity in your room. Mist diffusers are also a popular type of humidifier in Vietnam.
5. Cover with small gravel or bluestone
If you plant trees in a large area such as a garden, you can cover them with rocks or small pebbles to help retain moisture better.
6. Use glass cabinets, terrariums
Greenhouses are an option for maintaining very high and stable humidity for certain plants as low humidity can kill your plants.
Ideal soil moisture for some houseplants
| Houseplants | Ideal humidity |
| Aloe Vera | 30-50% |
| Aglaonema | 40-60% |
| Alocasia | 60-80% |
| Anthurium | 70-80% |
| Aspidistra (Cast Iron) | 40-60% |
| Bamboo | 40–70% |
| Begonia | 50–90% |
| Cactus | 10-40% |
| Colocasia | 65-75% |
| Coleus (Nettle) | 50-70% |
| Cordyline | 40–80% |
| Calathea | 50-60% |
| Dracaena (Prosperity) | 40-60% |
| Dieffenbachia (Dieffenbachia) | 60-70% |
| Epipremnum | 50–70% |
| Platycerium | 60–90% |
| Palm | 40–60% |
| Monstera | 60–80% |
| Homalomena | 60–80% |
| Fittonia (Velvet) | 50–70% |
| Fern | 50–70% |
| Orchid | 40–70% |
| Peperomia | 40–70% |
| Philodendron | 60–80% |
| Pothos (Betel) | 40–60% |
| Oxalis | 40–60% |
| Rubber fig (Red bud) | 40–60% |
| Spider plant (Orchid) | 50-60% |
| Sansevieria (Snake plant) | 40–60% |
| Succulents | 30-50% |
| Snake Plant | 40–60% |
| Syngonium | 50–80% |
| Tradescantia (Thai jasmine) | 40–60% |
| Zamioculcas Zamiifolia (ZZ plant) (Golden money) | 40–60% |
