How to Grow Rosemary Indoors: Surviving the Winter Safely

Known for its rich flavor and fragrant aroma, Rosemary is a must-have for any kitchen garden. While it’s typically grown outdoors in warm climates, growing rosemary indoors is both possible and highly beneficial, whether you’re seeking fresh rosemary during the winter months or simply lack outdoor space.

In this guide, we’ll walk you through everything you need to know about growing rosemary indoors. Let’s dive in!

Can You Grow Rosemary Indoors

Yes, you can absolutely grow rosemary indoors! Native to the Mediterranean, rosemary thrives in hot, dry conditions with plenty of sunlight. In USDA Zones 8 and above, rosemary can grow year-round outdoors, and some hardy varieties can even survive the winter in Zone 7.

However, in colder regions, rosemary can struggle to endure harsh winters. To protect the plant, it’s best to grow it in pots so you can bring it indoors when temperatures drop. Even in milder climates, growing rosemary indoors offers several advantages, giving you a fresh supply of this aromatic herb all year long.

Essential Tips for Growing Rosemary Indoors

To successfully grow rosemary indoors, you need to follow a few key principles. Here’s what to keep in mind:

Getting Started

You can start from scratch by either purchasing a plant from a garden center or taking a cutting from the garden. Varieties like Blue Boy, Salem Arp, and Huntington Carpet are all ideal for indoor growing. If you purchase a plant, be sure to transplant it into a slightly larger pot to give it room to grow. You can also sow seeds, but it takes longer and can be more challenging.

If you transplant from a garden, disinfect the plant before bringing it indoors to reduce the risk of fungal diseases like powdery mildew. A simple method is to use a diluted hydrogen peroxide solution (9 parts water to 1 part hydrogen peroxide). Spray the solution on the plant thoroughly 10 days before bringing it inside, again 5 days later, and once more on the day you move it indoors.

Light

Rosemary loves sunlight and needs at least 6 hours of direct sunlight daily. In summer, a window with the full sun or moving flower pots outdoors is usually sufficient. However, during the winter months, shorter daylight hours often make it difficult to meet this need, which is why many gardeners struggle to grow rosemary indoors in winter. 

This can be solved with artificial light. LED grow lights, which have a spectrum similar to sunlight, are an excellent option. They also consume less power, making them energy-efficient during winter when heating and electricity costs rise. Of course, if you have a window that provides at least 6 hours of direct sunlight, that works just as well.

Water

Watering rosemary can be tricky. Typically, it needs to be watered every 3 days in the summer and once a week in the winter, but this can vary based on local climate and indoor conditions. The key is to allow the soil to dry out between waterings, so always check the soil moisture first.

It’s worth noting that rosemary is an “upside-down plant,” meaning it prefers to absorb moisture from the air. Misting the leaves every 1-2 weeks can help supplement moisture, but avoid over-wetting the leaves to reduce the risk of mold or mildew.

Drainage

Rosemary does not tolerate waterlogged soil, as it can lead to root rot and other issues. When choosing a pot, make sure it has drainage holes and is the right size. A pot that is slightly larger than the root ball is ideal. If the pot is too large, excess soil will retain too much moisture, making the roots too wet.

Avoid using backyard soil, as it typically contains clay and drains poorly. Instead, opt for a well-draining potting mix designed for herbs or cacti. Alternatively, you can create your own mix by combining equal parts potting soil, perlite/pumice, and coarse sand.

Airflow

Airflow is crucial for indoor rosemary cultivation. Rosemary is susceptible to powdery mildew, and stagnant, damp air can promote mold growth. To prevent this, place your rosemary in a well-ventilated area, such as near an open window. If your indoor space is particularly humid, a small fan can help circulate the air and reduce moisture around the plant.

Fertilizer 

Fertilize rosemary once or twice a month during the growing season. Stop fertilizing in autumn and winter when the plant’s growth slows. Since rosemary is often grown for culinary use, it’s best to use organic fertilizers or compost. Well-aged compost, fish emulsion, or liquid seaweed are all excellent choices.

Prune

You can prune the top 1/3 of your rosemary before the end of spring to keep it compact and encourage new growth. If your plant has outgrown its pot, you can also trim the roots to keep it in the same container. To do this, carefully remove the plant from the pot, trim about 1-2 inches from the sides and bottom of the root ball, then refresh the soil with fresh potting mix.

FAQs

Q1: Can you grow rosemary indoors in water? 

Yes, you can propagate rosemary in water by placing a cutting in water until roots form. For long-term growth, it’s best to transfer the rooted cutting to soil.

Q2: Does rosemary grow well indoors?

Yes, rosemary can grow well indoors with sufficient sunlight, well-draining soil, and proper airflow. It also benefits from occasional misting and, in winter, may need supplemental grow lights. 

Q3: Do coffee grounds help rosemary plants?

Yes, coffee grounds can benefit rosemary in moderation. They provide nitrogen, improve soil structure, and aid drainage. However, avoid overusing them, as they can make the soil too acidic.