Houseplants may struggle when the air has too much or too little humidity, so it’s good to know the best home humidity levels for houseplants. There is no exact number that fits every climate and houseplant, but the range is usually somewhere between the 30-60% recommended by the EPA for general home humidity. Too much humidity can lead to mold, bacteria, gnats, and increased risk of root rot, while too little humidity makes the plant vulnerable to spider mites, scale, aphids, and other pests that thrive on warm, dry air. These are among the most common houseplant killers in which advanced infestations may require you to start over or fight an indefinite battle with houseplant pests. But the pests themselves are only one part of the reason houseplants struggle in dry air.
Low Humidity Levels and Houseplant Pests
It’s not just that common houseplant pests like dry, warm air. The plants themselves may be vulnerable due to low humidity levels. If you live in an arid climate, it’s only the most drought-resistant succulents that will live their best lives. Most houseplants can still grow and look good in drier climates, especially if you stay up on its watering and fertilizer needs. At the same time, you may have a houseplant that’s done well for years, but during an especially dry year or because an adjacent plant became host to a pest, this houseplant gets an infestation and is never the same.
Another reason houseplant pest control is harder with low humidity is that it adversely affects predatory bugs. One of the most effective forms of houseplant pest control is to introduce other bugs that prey on houseplant pests. This is especially true if you can identify the type of pest and then determine if it has a natural predator. One of the most common types of plant pests is the spider mite, but there is also a bug called the spider mite destroyer. The only problem is that predatory mites and other bugs that might serve as pest control aren’t viable in humidity levels lower than 50-60%. Most homes require a whole home humidifier system to maintain this humidity level.
High Humidity Levels and Mold Growth
People who live in a tropical or high-humidity climate need to be on the lookout for different warning signs. Too much humidity comes with its own set of risk factors including mold, bacteria, or fungal growth. Mold is the most common, but these problems are all treated pretty much the same. The first step is to physically remove as much of the mold as possible. For minor mold growth, you may be able to prevent new mold growth by increasing the ventilation and/or drainage so the soil can dry out between watering. More widespread mold may require repotting with fresh soil.
For further control and prevention, a simple home remedy is to dissolve one teaspoon of baking soda in one quart of water. You can also find many types of fungicidal treatments and products. These products are fine and good if you have them available, but don’t wait if you have baking soda ready to go. Better to treat the plant as soon as possible, and then follow up with targeted treatments as necessary.
What’s the Best Home Humidity Levels for Houseplants?
The best humidity levels for houseplants is usually within the high end of the range for a comfortable, healthy home. We frequently suggest somewhere between 45-55% to accommodate the widest range of plants. In general, it’s helpful but not essential for houseplants to have a whole house humidifier. Some houseplants including most succulents do fine with dry air, but many houseplants will do best with just a little extra humidity. If you live in a dry climate but want to grow more tropical houseplant varieties, some type of home humidifier may be essential. If you live in a tropical or coastal climate with high humidity, it’s important to maintain good ventilation in areas with houseplants. For seasonal climates, the time of year also plays a role with colder outdoor temperatures leading to lower humidity. Here is a handy chart of home humidity levels based on outdoor temperatures.