How to Mix the Best Soil for Rosemary (Indoors & Out)

There’s nothing like cooking with fresh rosemary harvested fresh from your own garden. From cooking meat dishes to infusing rosemary-inspired beverages, it’s one of the most delectable of all the culinary herbs you can grow at home, and there are different types of rosemary out there to suit even the most black-thumbed of gardeners. 

With the right soil, it’ll grow just fine as a charming indoor feature or outdoors in containers or beds. Here’s how to mix the best soil for rosemary – indoors or out.

Rosemary Overview

Scientific NameSalvia rosmarinus, prior to 2017 Rosmarinus officinalis
Common NameRosemary
OriginMediterranean region of Europe
USDA Hardiness Zones7-10
Size and Dimensions (Mature)Large shrub 120cm to 200cm tall (4 to 6 feet)
Distinguishing FeaturesDrought hardy aromatic herb, woody and upright growth habit
In-Home PlacementSoutheastern aspect; requires abundant light

Growing Rosemary Indoors vs Outdoors

a man planting rosemary plant in garden soil outdoor with garden shovel

Rosemary is a Mediterranean plant, a staple of dry hilly countryside and long, warm days. 

This popular perennial herb grows as an evergreen shrub that reaches a height of two meters (6 feet), though you can keep them in check with regular pruning. 

Growing Rosemary Outdoors

Grown outdoors in warmer climates, rosemary prefers sandy soil with good drainage, but it’s not fussy. 

It’ll also put up with loamy or clay soil and can handle acidic or alkaline soil with grace. They’ll thrive under soil pH levels that would knock out a lesser plant, although they prefer a soil pH between 6.0-7.0.

Rosemary needs a sunny location and won’t grow well without enough light. You should give them as much direct sunlight as possible, as they prefer at least 8 hours of sun per day. 

They’re suitable to plant outdoors in USDA Hardiness zones 7-10 and will do fine up to 11 and 12 if well watered and shaded during the hottest parts of the day.

Growing Rosemary Indoors

Indoor rosemary plants need the same things. They must be kept warm and dry, with good air circulation through their needle-like leaves. 

The hardest part is light levels – rosemary plants need as much bright, direct light as you can muster. 

Get them in a room with good southern or south-eastern exposure, preferably on a sill or close to a sunny window. 

A grow light is often the easiest way to ensure a healthy plant.

Growing Rosemary Indoors and Outdoors

Rosemary grown in containers can often have the best of both worlds. 

For those growing in regions too cold for rosemary to stay outdoors all year, it’s a snap to bring a potted rosemary inside before the first frost and return it to a porch or deck the following spring. 

They can sit out cold winters from the comfort of a well-lit sunroom, ready for the warm weather to return.

Secrets to Blending the Best Soil for Rosemary

potting rosemary plant in soil filled pot

Rosemary’s greatest weakness is at its root. They don’t like soggy soil, and while the plant is one of the most hardy herbs you can grow, too much water causes fungal diseases. 

Root rot is a common problem for over-watered indoor plants, and rosemary is no exception.

You can stave off problems like root rot and powdery mildew by focusing on what a potted rosemary plant needs to thrive. 

No matter the species, all potted plants need the same three elements – moisture retention, aeration, and nutrition.

Also, be sure to watch out for pests like root aphids when soil becomes overly moist. These critters can destroy a plant’s root system quickly, so be sure to keep your soil in check.

Low Moisture Retention

Moisture retention, sometimes called the water holding capacity, reflects how much water your mix will hold after a visit with the watering can. 

Some plants, like peace lilies, need a soil blend with lots of water retention. Others, like our rosemary plants, need far less.

To increase water retention, add organic materials like coco coir or peat moss

To reduce it, add more inorganic elements like sand, gravel or specialist amendments like perlite or volcanic gravel.

Good Aeration

All roots need good aeration to survive. It’s important that areas within the soil either drain quickly or hold onto small pockets of air even when the soil is wet. 

Soil that loses those air pockets becomes compacted and unable to support plant life.

Perlite, volcanic gravel, and clay pebbles all improve aeration. They hold air in their structure even when wet. 

Chunky elements like orchid bark, wood chips, and coarse sand encourage the water to flow through the soil quickly, allowing air pockets to form as it leaves.

Good Fertility

Organic matter not only increases the amount of moisture in the soil but it sets the stage for the ideal fertility and gives it the slightly acidic composition that Rosemary likes to grow in. 

Well-rotted compost, mulches, and manure are great for nutrition, and most well-made commercial soil mixes contain at least one of the above. 

If you have access to straw, take a look at our guide on how to use straw as garden mulch and apply the tactics to your rosemary!

Coco coir and peat moss do double duty, holding water and providing nutrients as they decay.

Remember, keep the soil fertility at average or even lower than average levels.

Rosemary comes from the sandy and gritty soils found in the hills of the Mediterranean, so mimic that as closely as possible for the best results. 

How to Mix the Best Soil for Rosemary in Pots

gardeners blending soil in rosemary garden bed

My favorite recipe for well-draining soil is one part perlite, one part coco coir, and two parts good-quality potting soil

Perlite provides good drainage and aeration, and coco coir holds just the right amount of water. 

A good quality soil blend holds it all together. 

I like to measure the dry components into a large tub or basin and then mix them thoroughly.

I add enough water to bind it together and then immediately use the resulting potting mix. 

It suits all rosemary varieties and is just as good for young plants newly rooted from softwood cuttings as for more mature ones.

How to Choose the Right Container for Rosemary

root bounded rosemary plants with different pots and garden tools

The right container is just as important as choosing the soil mix. There’s no point at all in putting perfect, free draining soil into a shoddy pot. 

The two most important factors are material and the degree of drainage. Get this right, and this tough plant will pretty much grow itself.

Unsealed terra cotta is best for a rosemary’s roots. It wicks water from wet soil and allows it to maintain the right hydration levels naturally. 

No matter how freewheeling you are with the hose or watering can, the rosemary will always have the right amount of water in its blend. 

You’ll need to ensure adequate drainage holes, no matter what pot you choose. 

Many terra cotta pots will only have one good-sized hole at the base and rely on their porous nature to allow the well-drained soil to dry. 

If you have opted for a non-porous material, you’ll need more holes than that. Three to five, equally spaced around the base, is best.

Potted Exotic Pro Tip: Next time you find yourself with more fresh rosemary sprigs than you need for a meal, consider propagating any leftovers! They’ll root from stem cuttings placed in nothing more complex than a bit of fresh water. 

To propagate, cut the end of the sprig cleanly, put it in a glass of clean water, and place it in a sunny spot. Once roots come in, you can place the newly formed cutting in its own little container of potting soil.

Planting Rosemary in Garden Soil

Rosemary is a tough customer. It’s a great choice to break up clay soil in your vegetable garden and provides an excellent cornerstone to any herb garden.

While Rosemary makes for the perfect companion to pots and planters, it can still be grown in standard garden soil. 

Companion Planting with Rosemary

I like companion planting rosemary with other Mediterranean herbs like oregano, parsley, or thyme as these require almost similar growing conditions and are also good at repelling mosquitoes naturally.

It’s a great way to flavor my own food with herbs that complement each other from my own rosemary plant and its neighbors.

Just make sure to plan your plants in a way that when these proceed to maturity, they are not tangled in each other and your garden is not giving out a chaotic garden vibe.

When to Plant Rosemary

When to plant depends on your location. Waiting for the right conditions will give your new plant the best start. 

In general, the best time to plant is just after the risk of frosts should have well and truly passed. 

For most, that’s mid to late spring, with warm areas to the south first off the block. Sowing in late summer is also a good choice for these fragrant herbs.

  • To prepare your soil for planting, turn through some well-rotted manure or compost a day or two prior to planting. This improves its nutrition and water retention. 
  • Next, add your herbs. Dig a planting hole as deep as the root ball, and do not cover the lower leaves.
  • Water the new herbs thoroughly and allow the soil to settle.

How to Care for Rosemary

watering potted rosemary plant via white watering can

Rosemary is an easy-care herb. Keep it warm, and it’ll produce new growth for you for years.

Full Sun Conditions

Outdoor rosemary needs full sun for as much of the day as possible. At least 8 hours of direct daily sun is preferred. Water when the top few inches of soil are dry. 

You’re better off giving them dry soils than ones with a lot of water gumming up the roots. 

Indoor rosemary will happily grow in direct sunlight, making it an excellent addition to kitchen windowsills or full sun planter boxes. 

Go Light on the Fertilizer

Go easy on the fertilizer. Too much makes the aromatic leaves less flavorful, so if you’re growing for culinary use, a single dose of slow-release granular fertilizer in early spring is plenty. 

For ornamental plants, more frequent feeding with a water-soluble balanced fertilizer encourages those gorgeous blue or white flowers. 

A second dose in the early summer is a good idea to spur blooms over the rest of the growing season.

Don’t Water Much / Keep the Humidity Low

Be mindful of their dry climate roots and only water rosemary when the potting soil is completely dry. 

You’ll also need to provide good ventilation, as they’re prone to leaf diseases like powdery mildew if kept in high humidity – or sometimes even in relatively humid conditions without airflow. 

For this reason, I do not recommend covering your rosemary plant with a plastic bag to promote moisture. 

Instead, consider an indoor humidifier so that you can control the humidity levels precisely. 

Keep An Eye Out for Pests

Rosemary is generally good at repelling slugs, snails, and other common pests, but that doesn’t mean you need to do no pest control at all. 

Spider mites and mealy bugs love nibbling rosemary herbs as much as we do!

Frequently Asked Questions About Rosemary Soil

potting rosemary plant in soil alongside an empty pot and a cat

What Type of Soil is Best for Rosemary?

Rosemary is an easy-going plant that will grow in most types of garden soil. They prefer sandy soil with good drainage but do fine in clay or loam. As long as there’s lots of organic material to provide fertility and keep the right soil moisture, the rosemary will thrive.

Can I Use Regular Potting Soil for Rosemary?

Rosemary will grow well enough in most good-quality commercial soil blends. You’ll get better results if you amend the soil to promote drainage. Perlite is one of the best choices, as it not only allows good flow through but also provides consistent aeration.

Where Does Rosemary Grow Best?

In the garden, Rosemary grows best in elevated, well-lit parts of the garden. In other words, rosemary grows best in full sun! It’s a great feature plant for higher, rockier aspects that may drain too quickly for other plants. 

While best known as a culinary herb, many varieties of rosemary are stunning as ornamental plants. 

The Tuscan Blue cultivar has gorgeous silvery foliage that is a feast for the eyes, and Creeping Rosemary is an excellent choice as an eye-catching ground cover. 

It has gorgeous blue flowers and is a fantastic feature for water-wise gardens.

Not only will it make your garden look colorful, but it will also help repel your feline friends preying on garden plants.

What Pots are Best for Growing Rosemary?

Drainage and root health are critical to growing rosemary in containers. The best way to ensure drainage is to use a container that has lots of drainage holes or is made of a porous material like terra cotta, concrete, or unglazed ceramic. 

This will prevent patches of stagnant soil from developing and keep the rosemary’s root system in tip-top shape. 

Well-drained soil depends on pots that allow water to flow away, after all.

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