How to Grow Rosemary Indoors Year-Round

Ever wondered whether it's possible to grow rosemary indoors? It certainly is, and it's not as difficult as you may think. Follow tips from horticultural expert Sarah Jay in this guide to growing rosemary indoors.

A shot of an herb near a window that is one method of growing rosemary indoors

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Some of the most commonly used aromatic herbs in a garden originate in the Mediterranean. Thyme, basil, and oregano are excellent additions to marinades, sauces, and even medicinal teas. But rosemary might be the most well-known among these.

This summer-loving woody perennial has so much use in cooking, but not everyone has the space to grow outdoors. Are you a person who struggles with mobility? Are you living in an apartment? Maybe you’d like to try to grow rosemary year-round, but you live in far North America where arctic winters knock any living thing out. Try grow rosemary indoors!

Rosemary plants do have a reputation for getting rather large, but that doesn’t mean the right conditions can’t contain them. With the help of grow lights, a grow tent, or a hydroponic system, you’ll have fresh herbs for cooking, teas, or medicines every season—even winter.

Methods For Growing Rosemary Indoors

A shot of multiple red-orange pots of aromatic herbs near a window in a well lit area
The plant can develop inside as long as the proper conditions are met.

Rosemary plants grow in any kind of indoor growing setting as long as proper conditions are met.

A large pot in a well-lit window with good soil will host a healthy plant. Keep the plant in your kitchen for easy access or in a bedroom to waft in its lovely smell while you relax. Growing rosemary indoors also means there is less likelihood of pests.  

If there is not enough sun in your home to host a potted rosemary plant, grow lights can help. Find a space in your home that can fit your potted plant and light. Any area that is large enough for your potted plant will most likely fit a small grow light as well.  

Grow tents are another option for rosemary and may be even better than lights as rosemary prefers high humidity. A grow tent keeps light and humidity in, giving you conditions that mimic rosemary’s favorite place to be: the Mediterranean coast.

There are different types of grow tents, but all require a little more space. If you have a lot of counter space, a full grow tent setup could be the indoor rosemary solution for you. 

Even though woody perennials like rosemary are prone to root rot in settings with too much moisture, hydroponics are another option that allows you to grow indoors. There are lots of different systems, but a setup that uses nutrient film technology is best. The only drawback to a hydroponic system is the amount of room you’ll need.

Planting

An overhead shot of a person wearing light-brown clothes planting several seeds in a peat pot on top of a covered surface in a well lit area
Propagation is possible through seeds or cuttings.

To start rosemary from seed, plant several seeds in a pot or starting container with a well-draining medium a few months before warm weather arrives. Although your goal is to grow indoors rather than outdoors, these plants have cycles they can sense anywhere.

Rosemary has a very low germination rate (about 30%), so sow several seeds at once. It also grows very slowly. Sowing in early winter is best. When seedlings have grown to a height of three inches, transplant them in a larger container or your hydroponic system. 

It’s easiest to propagate rosemary from cuttings. Just as you wouldn’t prune past the new green growth of a rosemary plant, use this same method to select cuttings. A rooting hormone helps roots develop.

Remove the bottom leaves, and dip the tips in rooting hormone before planting. You can plant several rooted rosemary starts in one container.

Start hydroponic seeds in a growing medium like coconut coir. Transplant starts into your system with fresh water and nutrients when roots begin to move through the medium. This takes about 1-2 weeks. When you transplant, space seedlings about six inches apart to provide enough room for a frequent harvest.

Because the water in a hydroponic system is flowing and clean, it will not cause rosemary to suffer root rot as traditional water propagation would. 

Caring For Indoor Rosemary

Once you’ve got your rosemary plants in place, there are a few essential conditions to meet. Follow these tips to learn how to care for rosemary indoors.

Light

A close-up shot of a growing aromatic plant in a light-blue colored pot near a window, basking in full sun
These plants prefer full sun exposure, at least 6 hours or more per day.

Rosemary plants love full sun, or six hours of sunlight or more per day. For people in the Northern Hemisphere, a south-facing window is best. The opposite goes for those in the Southern Hemisphere. Rotate the rosemary container or external light for full sun coverage.

Grow lights often come with a timer that allows you to set the amount of light per day. Start at six hours a day. If you notice the plant yellows or wilts, scale it back. If your rosemary plant looks stunted with just six hours, scale up from there. Lights with no timer setting need to be turned on and off manually. 

Water

A shot of a potted aromatic plant near a window being watered using a pink watering can in a well lit area
It is drought-tolerant and doesn’t require a lot of water to develop well.

Rosemary needs good drainage and little water when grown in the proper humidity. Water your rosemary plant only when potting soil is dry. In winter, water rosemary less.

Rosemary is drought-tolerant and doesn’t require a lot of water to grow well. Let the soil dry out between watering to prevent powdery mildew and other issues. Rosemary needs good air circulation, which will prevent problems like mildew that commonly affect rosemary (especially indoors). 

For hydroponic systems, change the nutrient solution every three weeks. Some NFT systems come with small domes you can place over the rosemary plant after it has been transplanted for humidity control. Test the dome for a trial period, and remove it if necessary.

As long as enough water is present, rosemary plants absorb enough to grow. Air circulation allows evaporation to wick away excess water that can damage the plant. 

Soil & Container

An overhead shot of multiple peat pots filled with soil and some scattered on the table with a person holding a label of an herb
Use a well-draining sandy soil in 12-inch-deep containers to cater to root growth.

Since this plant prefers sandy well-draining soil, you can use a soilless medium to host your rosemary. Soilless media are a combination of perlite, vermiculite, and peat moss or coconut coir, simulating the coastal ecology of the Mediterranean. Rosemary roots don’t need loam and prefer well-drained sandy soil to stay alive. 

Even though rosemary prefers sandy soil, it’s possible to grow this plant in a basic potting mix in a windowsill or under a light if you have some on hand.

Your rosemary plant will need a container at least 12 inches deep to accommodate roots. A terra-cotta pot is great because it draws moisture out of the soil and prevents root rot. Plastic containers are also suitable, but the soil will need lots of attention.

Plants growing in a hydroponic setting need to be checked frequently to ensure roots are healthy. Keep the water fresh and follow the guidelines that come with the system to keep roots from rotting. 

Self-watering pots tend to hold too much water for rosemary plants. Since rosemary needs to dry out between watering, plants growing in a self-watering container often get root rot and mildew.

Temperature & Humidity

A close-up shot of a growing potted herb near a window in a well lit area
These plants develop well in room temperature around 72°F.

Thriving in temperate coastal regions, rosemary plants are happy in room temperature (around 72°F or 22°C). Anywhere from high heat to low 30s (~0°C) is acceptable, too, although this likely won’t be something you’ll run into indoors.

Rosemary is very hardy but appreciates higher humidity. Avoid the dry heat of an air conditioning system. Water your plant more if there is no way to keep it away from a vent. Grow tents and hydroponic systems are great for maintaining the high humidity needed for a thriving rosemary plant. 

Fertilizing

A shot of a person using a spray bottle to spray liquid fertilizer on a growing aromatic herb that is placed in a white pot
Fertilizer is not needed unless it lost a significant amount of nutrients.

This herb doesn’t need much more than good drainage and the right medium to stay alive. No fertilizer is needed unless a significant nutrient loss is evident from yellowed leaves. In that case, a full-spectrum, balanced liquid fertilizer is recommended. Change the nutrient solution every three weeks in hydroponic systems.

Pruning

A close-up shot of a person wearing a white shirt and a grey apron using hand shears and is in the process of pruning stems of a plant that is placed in a small pot in a well lit area
Pruning the green tips can help the plant develop more.

Rosemary likes pruning, like many aromatic herbs. Since it’s a woody herb, prune the green tips on each branch to help it grow. You can do this all at once, or as needed.

In spring and summer, more growth will accompany pruning. In winter when it’s cold, reduce pruning frequency. Prune between growth points right at the bottom of new growth after the plant is established to encourage growth and keep the shape of the plant to your liking. 

If your rosemary plant grows flowers, deadhead them at the stem for higher herb potency.

Troubleshooting

A focused shot of a plant infected with powdery mildew showcasing the severity of the disease in a well lit area
Most issues stem from wet soil and lack of sunlight.

Since rosemary is so hardy and likes dry conditions, most problems stem from wet soil. It’s not often your rosemary plant will get upset in dry conditions or even from a lack of sunlight once it’s established. 

Powdery mildew can arise on needles if rosemary is watered from above. This mildew looks like yellowish-to-white powdery dust. To prevent powdery mildew, always water at the base of your plant.

Overwatering can cause mildew in the soil, or an overabundance of moisture retained in media can give fungus and bacteria the conditions they need to proliferate. A little bit of fungus or mold in the soil is normal. But the result of too much water in the soil is root rot.

Rosemary needs soil to dry out. If you keep it in a sunny or well-lit area, it should have no problem soaking up moisture in between watering. If bacteria or fungus become an issue, remove the rosemary and transplant it into a dry medium in a sanitized pot. 

Spider mites are pests that appear indoors on plants brought in from outdoors. If you have decided to bring your rosemary plant in from your garden for the winter, check for spider mites before bringing it in.

Spider mites weave a light web around needles. Look closely at the web before determining whether or not to treat with a commercial insecticidal soap. If multiple small bugs are crawling in the web, it’s spider mites. Always pick treatments that are safe for human contact for indoor grows. Damaged branches should be removed and discarded. 

Fungus gnats may hang around soil that’s too wet. These are small fly-like insects, and although they don’t hurt rosemary plants at first, they can reproduce in your growing medium and cause more damage as time goes on.

For fungus gnats, hang a sticky trap, or create a homemade trap in a small cup capped with plastic wrap that has holes in it. In the cup, put things that gnats like to eat, like fruit, or vegetable matter. Add a liquid solution of vinegar and dish soap. When gnats go to eat the veggies or fruit, they’ll fall into the solution and will be unable to leave the trap.

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