Bringing potted herbs inside for the winter seems like a simple way to keep fresh herbs on hand all season long, but the transition indoors often leads to a sudden decline in plant health. Many homeowners notice their herbs wilting, losing foliage or failing altogether within weeks of coming indoors.

You’re probably thinking that it’s because of low-light conditions indoors. But while it is true that some herbs will struggle with the reduced light that’s available indoors, insufficient sunlight isn’t always the primary reason why your outdoor herbs fail indoors. The main culprit is actually an incorrect watering schedule.

We’ve asked plant expert to explain why outdoor herbs fail indoors, how incorrect watering contributes to their decline and what specific rules you can follow to help your windowsill herb garden thrive throughout fall and winter.

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The Indoor Watering Mistake That Kills Herbs

In a nutshell, indoor herb gardeners often misunderstand the ways in which indoor environmental conditions alter soil moisture levels. Maintaining a summer watering routine during the colder, low-light months leads to soggy, oversaturated roots that quickly succumb to decay and rot.

When light levels drop, a plant’s rate of photosynthesis slows down, which directly reduces its water intake. At the same time, indoor ambient temperatures and humidity levels shift. Indoor heating can cause the top layer of soil to dry out rapidly, while the soil deeper down near the root ball frequently stays saturated.

If you water your plants whenever the surface appears dry, you risk drenching roots that are already sitting in moisture, creating an oxygen-deprived environment, which is how root rot sets in.

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“A sunny spot on your windowsill, well-draining soil and moderate watering are your best strategies for growing [herbs[,” says Marina Prokaten, the Plantum app resident gardening expert.

With that general guidance in mind, what “moderate” means varies depending on the exact herb you’re growing. Let’s dive into how to water different types of herbs once you bring them indoors for the colder months.

How to Water Herbs Indoors: Mediterranean vs. Moisture-Loving Herbs

Preventing root damage requires tailoring your watering strategy to the specific herb variety, as different plants have drastically different moisture tolerances.

Low-Water Mediterranean Herbs

Woody, Mediterranean varieties naturally prefer drier conditions and are particularly susceptible to root rot when overwatered indoors:

• Thyme: Donna Letier, co-founder and CEO of Gardenuity, emphasizes precise watering care for this herb, advising gardeners to “plant [thyme] in well-draining soil and water only when the top layer feels dry.”
• Oregano: This herb craves direct light and arid conditions. As Marina Prokaten notes, “Oregano loves hot, dry and sunny places, so your east- or south-facing window will be perfect for this plant.”
• Rosemary: Indoor gardeners typically have a bit more trouble with rosemary because it does not like overly dry air. Still, you might succeed in growing it if you can find a humid but sunny spot (say, your kitchen windowsill) and water only when the top layer of soil has dried out.

Moisture-Loving Herbs

Other soft-stemmed herbs require consistent moisture to thrive, but still demand well-draining soil to protect root systems during winter:

• Chives: According to Peter Ivanov, gardening expert at Fantastic Services, balance is essential when watering indoor-grown chives: “Plant them [chives] in potting soil and keep the soil slightly damp, watering when the top layer feels dry.”
• Basil: This popular kitchen herb should not be allowed to dry out too much. Basil “prefers to stay warm and well-lit and needs regular watering,” Prokaten advises.
• Mint: Mint is super-easy to grow indoors; even a beginner herb gardener can tackle it. “It thrives in bright, indirect light and prefers consistently moist soil,” Letier says.

The Proper Winter Herb Watering Protocol

To prevent root rot while keeping indoor herbs healthy through the winter, follow this core care checklist:

• Test the Soil Depth: Do not rely on a visual check of the soil surface. Insert your finger one to two inches into the soil to verify that it is actually dry before adding water.
• Ensure Adequate Drainage: Always use containers equipped with drainage holes and well-draining potting soil so excess water can escape freely.
• Position for Maximum Light: Place sun-loving herbs in bright spots, such as an east- or south-facing window.
• Avoid Calendar-Based Schedules: Water only when the plant’s soil conditions and specific moisture preferences require it, rather than sticking to a rigid weekly timetable.

Sources:

• Donna Letier, Co-founder and CEO of Gardenuity
• Marina Prokaten, Plantum app resident gardening expert
• Peter Ivanov, Gardening expert at Fantastic Services

This article has been adapted from 12 Best Herbs to Grow Indoors This Winter by Ashley Zlatopolsky