Rosemary is a beautiful and delicious herb. Keeping a rosemary plant alive indoors is a little tricky, however. Follow these tips to keep your potted rosemary alive inside.
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How Not to Kill Your Rosemary Plant
I’ll never forget the disappointment one fall, when I brought my beautiful rosemary plant inside before winter set in, only to have it die within a month. Like my other houseplants, I had given it what Mark Shepard of Restoration Agriculture calls the STUN treatment–Sheer Total Utter Neglect.
The rosemary plant had enjoyed this type of treatment outside, so I figured that would ring true for the indoor experience. I was apparently mistaken.
The following spring we headed to the farmers’ market to replace the unfortunate rosemary plant. That was 5 years ago, and I’ll never forget what I learned from a very wise farmer. She gave everyone a pamphlet with their purchase: “How NOT to Kill Your Rosemary Plant”.
The fact that she even had a pamphlet made me feel a little better about my murder of that previous year’s plant! I wish I could track down that pamphlet today, but at least the information is still alive in my brain.
If you live in California, you probably think I’m a little cooky. Visiting California last year, I saw how the ever-flowering rosemary shrub was used as an anchor perennial landscape plant. In our neck of the woods–USDA hardiness zone 6–rosemary rarely survives the freezing winters outdoors.
Best to keep it in a pot and move it inside for the winter. Still, others may keep rosemary inside as part of a year-round, windowsill herb garden. The care will be the same.
Rosemary’s Native Climate
Knowing about rosemary’s history can help us figure out how to deal with it once we have it inside. Rosemary is a native Mediterranean plant, hailing from a region of dry, well-drained soil and hot, sunny temps.
Rather than getting its moisture from the soil, rosemary is accustomed to grabbing moisture out of the sea-sprayed air. This knowledge can inform our care of an indoor rosemary plant.
Pick The Right Pot and Soil
Pick a pot that matches the size of your rosemary plant. For example, if the above-ground growth is around 8-inches tall, your pot should be at least 8-inches deep. The width should allow at least one inch of space between the roots and the side of the pot.
You can increase the size of the pot as it grows over the years. If you want to keep the plant a certain size, root pruning will help you keep it happy (read below).
Create Proper Drainage
Rosemary is called an “upside-down plant” because it likes dry roots and prefers to absorb moisture from the air through its foliage.
In addition to growing rosemary in a pot with a drainage hole, we need to take an extra step: Add a layer of gravel or small rocks to the drainage pan, so that the pot actually sits on top of the rocks, rather than in the pan.
You don’t want the potting soil to have contact with water in the drainage pan.
Let the Light Shine Through
Rosemary needs full sun, whether inside or out. When inside, our rosemary plant sits on a laundry room shelf in a bright, sunny window, and seems just fine with the sun coming through the glass block window.
How to Water Rosemary
Outside, I water my rosemary plant about twice a week, which is pretty standard for potted outdoor plants.
How you handle watering the plant inside is crucial, however. It seems like too much water is a bad thing because it doesn’t like wet feet, right? True, but not enough water can spell death, too.
Indoors, water the soil every two weeks (check to make sure soil is dry first), but always keep water in the drainage pan with the rocks in it. Because the plant likes to absorb moisture from the air, it will enjoy the water as it evaporates from the pan.
Indoor air is usually drier than outdoor air. For that reason, and because rosemary is an “upside-down plant”–liking dry roots but moist foliage–fill a spray bottle with water and mist the foliage once or twice a week.
Fertilize your rosemary plant in the spring. Start one month before you plan to move your rosemary plant outside for the summer. For me, that means around April Fool’s Day. I use a fish fertilizer diluted as directed in the regular watering schedule.
I fertilize the rosemary about 2-3 times before moving it outside mid-to-late May.
Each spring, evaluate your rosemary’s size, repot it in new soil, and prune the roots as needed.
Sizing Rosemary to the Pot
Rosemary will only get as big as the pot it’s sitting in. Once the above-ground plant looks to be about the same height as the pot, it’s either time to move it to a bigger pot or prune the roots so that they aren’t too crowded.
If roots are left to grow, they will eventually take over the entire pot–becoming “root bound”–and will keep the plant from absorbing enough nutrients and water. The foliage will look more lackluster over time and eventually die.
Changing the Soil
After each season, your plant will have extracted all of the nutrients available in the potted soil mix, so in the spring you’ll want to repot rosemary with new potting soil. This is a good time to check the roots and root prune if necessary.
If your rosemary has outgrown its pot, you can prune the roots to keep your plant growing in the same pot. Gently wiggle the whole plant out of the pot (roots and all). Are the roots running tightly around the perimeter?
If so, it has outgrown the pot. Using sharp garden scissors, cut about 2 inches of root matter off the bottom and sides before repotting it with new soil. Keep the plant in the shade for a couple of days while it acclimates to the changes.
It may seem like a lot of work to keep a potted rosemary plant happy indoors, but it’s an easy procedure once you get the hang of it. Plus, the taste of fresh rosemary roasted potatoes in the middle of winter can’t be beat.
Need more ideas for growing and using herbs?
Are you looking for strategies for your permaculture garden? You’ll find loads of information in my book, The Suburban Micro-Farm.
Have you kept your rosemary plant alive indoors?