By Dr. Mercola
Rosmarinus officinalis, more commonly known as rosemary, is a woody, perennial herb that is fragrant, evergreen and native to the Mediterranean. While some gardeners plant a rosemary bush in their garden to harvest the herb, others use it to add beauty and fragrance, without ever using the leaves.
The plant has needle-like leaves similar in appearance to hemlock. It flowers in pink, purple or blue in spring and summer in temperate climates, but may flower constantly in warm climates.
Rosemary may be used in multiple ways in your home and is extremely hardy. This means it fares well both inside and outside, in the ground or in a pot. Although it loves the light, heat and humidity are not a must, making indoor growing easier than other herbs. As an herb it's mostly used in seasonal dishes, but it is also commonly used as an ornamental landscape planting that has the benefit of being both beautiful and fragrant.
Interestingly, this herb may grow upright or as a trailing plant along the ground.1 As a prostrate plant it offers aromatic ground cover to your garden that may be harvested throughout the growing season. The blue flowers of the trailing rosemary plant are attractive to bees, offering nutritional benefits to you and supporting the local bee population.
While you may consider bees buzzing in your yard a nuisance, colonies are vital to agriculture as one third of the U.S. food supply depends on bee pollination.2 Those plants include avocado, nuts, citrus fruits and berries, to name just a few. Planting and cultivating a rosemary plant is not difficult and may bring you years of seasoning for your kitchen and perfumed landscape pleasure.
Soil pH Is Important to Your Rosemary Plant
The rosemary bush is a woody growth that is easy to plant and care for. It's probably best to start from cuttings or an established plant, as germinating from seed may take up to three months and harvesting your first herbs from seedlings may take another couple of years.3
Plant growth and watering requirements will depend on the area where it's planted. When grown in a pot you may bring it in during the winter months to enjoy the aroma and seasoning all winter long. If you are planting it outdoors, remember it grows best in hardiness zones 6, 7, 8 and 9.4 You can find the hardiness zone for your ZIP code by visiting U.S. Department of Agriculture (USDA) Research Service.5
Rosemary loves at least five hours of direct sun during the day and a sandy, loam soil that drains well. The plant does well when the pH of the soil is between 6 and 7. You may purchase a pH soil test kit at your local gardening shop or use one of these two simple at home tests. The pH of your soil is a rating of acidity or alkalinity with 7 being neutral. Before adding any amendments to the soil, start by doing a pH test.
Any additions you do make to move the pH toward neutral should be made in small amounts over time to ensure they work before adding more. The two tests you may try without using a chemical test kit are:6
✓ Vinegar and baking soda
Collect 1 cup of soil from around the area of your garden you want to test. Mix it well. Place 2 tablespoons of the soil in two separate containers. In the first container holding 2 tablespoons of soil add 1/2 cup of white vinegar. If the mixture bubbles, your soil pH is alkaline and above 7.
If it doesn't fizz, use the second container with 2 tablespoons of soil and add distilled water until the soil becomes muddy. Next, add 1/2 cup of baking soda. If it fizzes the soil is acidic with a pH likely below 6. If there is no reaction, then the soil likely has a pH between 6 and 7.
✓ Cabbage water test
Simmer 1 cup of cut up red cabbage in 1 cup of distilled water on the stove for five minutes. Let it cool for 30 minutes before straining off the liquid, which should be purple/blue in color. The pH of this liquid is 7. Next, add 2 teaspoons of soil to a jar and a few inches of cabbage water. Stir this up and let it sit for 30 minutes. If the water turns pink then the soil is acidic with a pH less than 6; if it turns blue/green the soil is alkaline, with a pH over 8.
According to Mother Earth News, making amendments to your garden soil to reach near neutral pH may be as simple as adding composted material.7
"Raising the organic matter content of soil will usually move the pH of both acidic and alkaline soils toward the neutral range. This is because organic matter plays a buffering role, protecting soil from becoming overly acidic or alkaline.
Finished compost usually has a near-neutral pH, so regular infusions of compost should be the primary method you use to improve soil with extreme pH issues. If your pH readings are only slightly acidic or slightly alkaline, compost and organic mulches may be the only amendments you need to keep your crops happy and your garden growing well."
Planting an Established Plant or Propagating Your Rosemary From Cuttings
If you have purchased a small plant from the garden store, you'll want to dig a hole as big as the pot the plant comes in, as demonstrated in this short video. Press on the side of the pot all the way around and on the bottom to loosen the soil and small roots from the side, so the plant and entire root ball slides out easily. Once out of the pot, loosen the soil around the roots and place it in the hole. Backfill the hole with soil and tamp it down to remove air pockets around the roots.
Rosemary plants grow slowly the first year after planting and pick up speed in the next years. If you want to harvest a significant amount of the herb by your second year, you'll want to forgo a smaller plant and opt for a larger pot.8
In warmer climates they grow quicker, so you'll want to plant them at least 3 feet apart to allow ample room for growth. If you live in northern climates and commonly experience freezing weather lower than 15 degrees F, you'll want to grow your rosemary in a pot and bring it in during the winter months.9
While inside, keep the plant in a south facing window and do not harvest if it is not actively growing. By the end of winter the plant may appear a bit raggedy, with dried up needles and sparse stems. However, after hardening off the plant, place it outside and it should return to full health rather quickly.
The hardening process allows the plant to get used to being in full sun and helps prevent shock.10 It's easily accomplished by setting the plant outside for two to three hours the first day and gradually increasing the time over 10 days until it is outside full-time.
Cuttings are another way of starting a strong rosemary plant in your garden. These plants will establish more quickly than plants that are started from seed.11 Often it will reach usable size in just a few months and will have the same flavor, hardiness and growth of the original mother plant. Select a healthy stem with fresh growth. Avoid stems that have gotten woody as they don't root as easily. Using sharp scissors, snip it 5 to 6 inches from the tip and take several cuttings to ensure at least a couple that will root.12
Strip off the lower leaves and place it in a jar of water in a warm area away from direct sunlight. Change the water every couple of days with room temperature water to avoid shocking the plant. It takes a few weeks, or longer in colder weather, for the stem to start growing roots. Once roots develop, pot the plant in soil that drains well, taking care to avoid damaging the roots.
Keep the plants out of direct sunlight until the roots are established. Once you've planted either a pot or cutting outside, consider watering once a month in the first three months with a seaweed solution to help the plant get established in the soil.13
Caring and Harvesting Your Plants
Once planted in the soil, taking care of a rosemary bush is relatively simple. The plant does best in dry soil and is prone to root rot. Allow the soil to dry out before giving the plant a good watering. Soil that drains well will help reduce the amount of water that sits for long periods of time against the root system. Good air circulation around your plants is an often overlooked tool that reduces the amount of dampness that remain around your plants.14
Dampness around plants is a perfect setup for the growth of mildew and a draw for many insects, such as slugs and fungus gnats. A strong breeze helps reduce insect damage since they can't settle on the plants for long and helps to evaporate moisture. Rosemary bushes are not affected by many pests. However, they are bothered by whiteflies, spider mites, scale and mealybugs.15 Keeping the plants clean, dry and in the sun helps to reduce the potential risk for insect damage.
The rosemary bush doesn't require frequent fertilization. One treatment in the early spring with a fish/kelp emulsion will start the plant out well for the season16 and provide you with good harvest. During the spring season your plant requires a good pruning after it flowers.17 This helps to better shape the large bush and fill in areas with new growth so the plant doesn't become spindly. During pruning it is not good to take more than one-third of the plant at a time and important to make your cuts above a leaf joint.18
Remove branches that cross each other so they don't get heavy. You may want to prune lightly throughout the year to keep the plant in check. Rosemary bushes can also be pruned into topiary figures in your yard. The new shoots may be harvested to keep the sculpture shape and provide you with the herb for cooking.
When harvesting rosemary, snip the tender end shoots that aren't woody as they are the best to use in your cooking. If you want to dry some rosemary for use in wreaths or to store for use in the winter months you'll clip the same type of tender shoots and tie several together in bunches at the base of the stem. Hang these upside down in a cool dry area.19
Once the stems are dry you can strip the leaves by running your fingers along the stem. Rosemary may also be preserved by freezing the sprigs. Alternatively, the leaves may be dried flat and stored in an airtight container.20 Although the aroma and flavor blends well with other herbs, it can also be used alone in soups, stews, vegetables and sauces.21 The dried herb may be used in bathwater, bouquets, wreaths and sachets. Freshly harvested rosemary makes a great addition to wine, olive oil, butter and garlic.
Health Benefits and Drug Interactions
Not only is rosemary a fragrant herb that works well in your cooking and scented home décor, but it also has medicinal benefits. The herb may have significant side effects and medication interactions when used in concentrations higher than what you would find in infused oils or stew. As a member of the mint family, it is a rich source of antioxidants and anti-inflammatory compounds that play an important role in neutralizing the effects of free radicals.22
Rosemary contains carnosic acid that appears to have some protective effects against brain damage following stroke and neuroprotective effects.23,24 Some studies have even found rosemary will help prevent aging in your brain.25
Some cooking methods increase the number of cancer-causing compounds released in meat, such as grilling. In one study, researchers found when rosemary was added to ground beef it reduced the number of carcinogenic compounds that were formed.26 Other research found rosemary extract could slow the spread of leukemia and other carcinoma cells.27 Yet another study found rosemary was a potent anti-inflammatory and possible antitumor agent.28
Traditionally, rosemary has also been used to alleviate bloating, constipation and upset stomach and is an effective breath freshener.29 The antiaging properties of rosemary may also have an effect on your skin, healing blemishes and wounds,30 and increasing the natural shine of your skin.
These benefits come with a warning. The essential oil should never be consumed,31 but rather used topically, as the potency of the product may lead to significant side effects including spasms, vomiting, pulmonary edema (fluid in your lungs), coma and death.32
There is also evidence that large amounts of rosemary may trigger miscarriage in pregnancy, so it's wise to steer clear until after your child is born.33 Rosemary supplements or the addition of large amounts in your culinary efforts may affect the activity of some medications, including:34
- ACE inhibitors (blood pressure)
- Anticoagulants (blood thinner)
- Lithium (treatment of manic depression)
Can You Improve Your Memory With Rosemary?
It is believed the ancient Greeks wore garlands of rosemary while studying to help their memory and learning.35 There are three different types of memory to which you have access.36 Your past memory is made of experiences you had in the recent and distant past. Your working memory is what you do to organize your day and the memory you depend upon to get from breakfast to dinner. Your future memory is what you draw upon when you want to "remember to remember" something.
Rosemary appears to have an action on your working memory and your ability to concentrate on your current situation.37 Researchers used 20 volunteers to test cognitive performance after exposure to the fragrance of rosemary oil.
Blood samples from the participants demonstrated they absorbed a component of the oil from the fragrance, the amount of which depended upon the amount of oil they inhaled. Next the researchers measured the participants' speed and accuracy on cognitive tests to determine the effect this compound might have on performance.
Results demonstrated exposure to rosemary oil improved both speed and accuracy of cognitive performance at a rate that was greater for higher amounts of oil inhaled. Another study tested the differences in performance between lavender and rosemary scents in 144 people over the age of 60.38
The participants were challenged to remember items in a room while participating in word puzzles. Researchers found those who inhaled rosemary did statistically significantly better than those who inhaled nothing, while those inhaling lavender did worse. Aromatherapy has a high safety profile with few side effects and rosemary seems to be a perfect addition to your daily routine. It may improve your performance at work, with your family and may help you find greater enjoyment in your everyday life.