How to Grow Rosemary from Seed

Growing Rosemary

Like several woody perennials such as lavender and thyme, rosemary is a Mediterranean native celebrated for its tenacious and frost hardy tolerances. More than two dozen cultivars of Salvia rosmarinus (formerly Rosmarinus officianlis), rosemary thrives in many climates across the country as a low-growing and hard-to-kill shrub known to live for up to 10-20 years.

Rosemary regularly performs as an outdoor perennial in hardiness zones 6-10, going dormant during freezing winters in more northern climates. And like its perennial relative lavender, rosemary can be notorious for a low and slow germination rate but, once you successfully germinate your first couple of starts, you’ll come to find that the only real secret to growing rosemary is patience.

Whether growing from seed or propagating from a cutting, nothing beats the garden fresh fragrance of rosemary, even in the dead of winter.

How to Grow Rosemary from Seed

• 2-6 week cold-stratification
• Press into soil without covering
• Begin more starts than you’ll use

Although rosemary seeds mature into a woody and frost-hardy evergreen, they are somewhat notorious for being delicate with a low germination rate and about 14-28 days required for those that do come up.

Rosemary will require some patience in the beginning, yet is a very rewarding plant to bring to maturity. Like many herbs and flowers, rosemary seeds benefit from a process of cold stratification, which simulates a brief winter dormancy that the seeds would otherwise experience if having been grown in the wild.

Harden off rosemary seedlings before transplanting outside into a sunny place in the garden into average, loamy, and slightly acidic garden soil.

Rosemary Soil

Perennial Mediterranean herbs such as lavender and thyme require the dry, rocky, and shallow soils native to the region and promise to thrive in any garden able to offer such conditions.

Rosemary is widely grown in pots and containers because they offer the thorough and reliable drainage necessary for plants to thrive perennially. If growing in a container, try blending even parts sand and perlite into the potting soil before transplanting for even better drainage.

Soil is best if allowed to dry out between watering because Salvia rosmarinus is susceptible to mold, mildew, and rot in humid and poorly drained gardens. Unlike fruit-bearing crops such as tomatoes and eggplants, rosemary is not a heavy feeder and generally performs well without the use of fertilizers. Rosemary does best in slightly acidic soil with a pH of about 6.0-7.0.

Watering Rosemary

Is Rosemary A Perennial?

Once established, rosemary is a tremendously hardy and tolerant perennial known to live up to 15-20 years with optimal pruning and overwintering conditions.

Rosemary can overwinter perennially in zones 7-11 as matures plants can withstand a minimum frost point of about 0-10° F before declining. However, rosemary is popularly grown in convenient moveable pots and containers because it can safely overwinter indoors and be returned back outside as soon as temperatures warm to a comfortable 20° F or better.

If bringing rosemary indoors to overwinter, be sure to give it plenty of light (south-facing window is best) and minimal waterings, as rosemary naturally thrives in average and medium dry soil.

Rosemary in Winter

However, growers in warmer and more southern hardiness zones will experience year round rosemary growth. Rosemary grown in pots and containers can be conveniently moved indoors to best manage perennial development.

Growing Rosemary in Pots

One of the main benefits to growing anything in a container or pot is that they drain quickly and thoroughly and are an ideal means for flowers, herbs, and crops that require drier, well-drained soils.

Like other woody and herbaceous culinary herbs, rosemary prefers a slight drought in average, loamy, and well-drained soil. Be sure not to overwater as rosemary plants are susceptible to mildew and rot from overly humid and saturated growing conditions. Pots and containers are convenient for full sun varieties because they are able to be moved and relocated hourly to track the sun or moved in and out of the house to capture optimal daylight.

While many rosemary plants may be comfortably established outdoors for perennial growth, others grown in more volatile hardiness zones will benefit from container gardening simply because it can be brought in each year to overwinter.

Rosemary grown in the garden may be uprooted and transplanted to a container for indoor overwintering.

Growing Rosemary Indoors

Whether transplanting rosemary outdoors or keeping it indoors for some quick, small, but flavorful sprigs, be sure to follow the same seeding and cold-stratification instructions as mentioned above. After keeping rosemary under a grow light for the first 8-10 weeks, be sure to place the seedlings in plenty of natural light, preferably near a south-facing window.

Rosemary plants can thrive indoors, provided they are given plenty of full sunlight. One of the leading benefits to growing rosemary indoors is that the pots and containers generally dry and drain more thoroughly than in the garden bed.

Rosemary performs best indoors when able to be moved around outside during the warmer growing season and brought back in for winter in hardiness zones 6 or colder.

Pruning Rosemary

Rosemary is a cold-hardy perennial known to live 10-20 years or more when given proper care and a scheduled pruning. Similar to lavender and sage, rosemary will live longer and healthier if pruned at least once a year to help promote the newest, most vigorous growth.

Pruning rosemary may seem intimidating at first because it grows so woody and thick, but proper pruning only requires us to cut from the softer and greener stems.

When pruning rosemary, a good rule of thumb is to trim the entire plant back by about a third of its overall growth. Pruning helps shape the plant, keeping it tight and rounded to be maintained as a convenient potted variety or as a low-growing outdoor herb.

When to Prune Rosemary

How to Prune Rosemary

Instead, only prune about ⅓ of the total length of any rosemary stem to help ensure that only soft, green growth is pruned, initiating the healthiest and bushiest plant possible.

Propagating Rosemary

Rosemary is one of the easiest and most reliable plants to grow from cuttings and is widely preferred to seed propagation. While rosemary seeds can take 14-28 days for germination and even longer than that for cold stratification before sowing, cloning rosemary from established plants is nearly effortless and can keep you in a yearly supply of tender garden fresh rosemary.

Propagating rosemary from cuttings is no different than pruning or harvesting and follows the same general guidelines for propagating nearly any other kind of plant.

Although propagating rosemary from cuttings is without argument the easiest way to produce rosemary, doing so will strictly limit the varieties possible to grow since many greenhouses and nurseries will only cater to the most 2 or 3 popular types. Regardless if rooting hydroponically or directly in soil, clones should be rooted and ready to transplant after about 3-4 weeks.

4. If propagating rosemary hydroponically in a glass of water, be sure to change out for fresh water and a new glass every 5-7 days to avoid mold. If propagating rosemary cuttings directly into soil, rooting hormones and gels are popularly used to incite growth, but are not required.

Rosemary Companion Planting

When grown outdoors in the garden, rosemary has been widely considered to be a beneficial companion plant for many fruit and vegetable crops. A mature 36-48” tall and wide herbaceous rosemary plant faces little threat in the garden from either climate conditions, insects, or disease.

Rosemary produces a few chemical compounds that are credited for its unique and robust fragrance, while making the surrounding area inhospitable to smaller pests and insects.

Three of the chemical compounds found in rosemary (carnosic acid, carnosol, and rosmarinic acid) are extracted from the plant to create various types of pesticides both organic and synthesized.

Many plants that emit naturally repelling chemicals are often believed to be more effective when directly grown in the garden rather than a container. When grown in the garden bed, plants like rosemary and marigold that emit naturally occurring pesticides are able to establish these chemicals in the soil to best mitigate pest problems.

However, when grown in a separate pot or container, rosemary is only able to emit its robust fragrance and inhospitable terpenes rather than permeate them throughout the soil.

Rosemary Flowers

Edible and fragrant when allowed to flower, Salvia rosmarinus produces countless dozens of powdered blue and lavender blooms that look strikingly similar to orchids.

That’s right, orchids. Non-flowering rosemary stems are a popular green filler for fresh cut arrangements and design work despite its flowers still underutilized in the floral industry.

Most gardeners can expect their rosemary to begin blooming in late spring to early summer but rosemary is known to occasionally flower out of season, allowing for a much longer flowering window.

Like many herbs, since garden rosemary is typically not allowed to flower, these semi-rare and exclusive blooms are greatly desired by bees, butterflies, and other beneficial insects.

Harvesting Rosemary

Unlike lavender which is almost strictly grown and harvested for its fragrant blooms, rosemary is harvested for its perennially aromatic stems and can be harvested as needed nearly any time of year, not just spring or summer.

Harvesting rosemary follows the same basic guidelines as pruning or propagating and experienced gardeners will often take the opportunity to prune, propagate, and harvest all from the same cuttings.

While many herbs can lose their fragrance with maturity, rosemary is known to maintain it even under a pile of winter snow.

If harvesting for culinary use, it's recommended to only harvest smaller and newer growth since these younger cuttings will be less woody, more tender, while boasting a more refined fragrance.

Rosemary is popularly grown indoors as an easily accessible and nearly endless supply of fresh herb all from the convenience of the kitchen.

Garden fresh rosemary shouldn’t require too much washing before use, while cuts harvested from store bought plants should be thoroughly rinsed since commercial plants have likely been chemically treated.

Drying Rosemary

Because rosemary is traditionally harvested for its vegetative growth and not for flower production, it has a very similar but slightly different dehydration method from its relative lavender.

Rosemary sprigs are easily dried using one of three common methods and can be quickly ground into a homemade herb spice in just minutes.

Dried rosemary is a world-class ingredient used to craft artisan cheese, oil, vinegar, salt, butter, and bread as well as classic roasts.

While your own homegrown rosemary is likely organic and free of pesticides, always be sure to rinse rosemary before dehydrating because store bought plants are almost certain to have been chemically treated.

How to Dry Rosemary

Hang Dry: Cut about 6-8” of newest growth per stem and then bundle together. While larger plants will yield longer stems, still harvest just the tips for best flavor. Hang the rosemary bundle upside down in a dry, cool, and well-ventilated area for 7-14 days until evergreen nettles are brittle and no longer pliable.

Oven Dry: Do not place 6-8” woody stems into the oven. Instead, cut down into small 2” tips and discard any overly thick and woody pieces. Line a baking sheet with parchment paper and place 2” cuts on the sheet and into a convection oven at 175° F for 10-15 minutes or until leaves and stems are brittle and have lost color. After 10-15 minutes, turn off the oven and allow rosemary sprigs to remain in the oven for another 40 minutes, leaving the oven door open to cool.

Food Dehydrator: Herbs, fruits, and flowers are ideal for countertop food dehydrators for reliable and thorough drying. Food dehydrators feature step-by-step instructions for herbs and is the preferred method for many cooks and home gardeners. Many herbs such as lavender should only take about 2 hours in any household food dehydrator.

Types of Rosemary

Salvia rosmarinus (formerly Rosmarinus officinalis) features more than two dozen unique cultivars of rosemary including 4 varieties that have earned the Royal Horticultural Society's Award of Garden Merit, one of the UK’s most distinguished gardening achievements.

Regardless of cultivar, rosemary shares the same tolerances to neglect, drought, and poor soils and each has their own specific tolerances to freezing and subzero conditions.

One of the most popular cultivars of rosemary known as Arp is an American heirloom widely understood to be the most winter-hardy variety, able to withstand outdoor winters down to about -10°F while other varieties may only be able to comfortably overwinter down to around 30°F.

While common rosemary is typically grown as the preferred culinary variety for enhanced flavor and aroma, take a tip from the pros and try award-winning Tuscan Blue or Miss Jessopp’s Upright for an even more elevated dish. Blooms within Salvia rosmarinus range from a light powdery blue to lavender.

Benefits of Rosemary

Rosemary Tea

Garden fresh rosemary tea is traditionally made from common lavender (Salvia rosmarinus) because it is widely known to produce the most fragrant and flavorful stems.

Rosemary tea can just as easily be made from garden fresh sprigs harvested that morning as it can from dried herbs stored in the cupboard. Just like any freshly harvested herbal tea, rosemary is easy to brew and takes no longer than 10 minutes.

Rosemary tastes excellent by itself but lends well as a part of a much more herbal blend consisting of lavender and thyme. Brewing rosemary tea makes the raw oils more palatable and digestible for consumption.