Choosing soil for rosemary has never been the easiest thing for gardeners to manage, and a large number of rosemary plants have been sacrificed in the process.
I’ve heard many troubling stories of people who ended up killing their rosemary by planting it in the wrong soil.
Yes, rosemary is notoriously delicate when it comes to its soil needs, but actually it’s not very hard to find the mix that best suits this wonderful herb.
Below, you’ll find all the information I can give you to help choose the ideal soil for your own rosemary growing.
Hopefully, through reading this, you’ll see that it’s just a matter of understanding how this versatile herb grows in and reacts to, its environment.
Understanding Your Rosemary Soil Needs
I once heard an experienced gardener say that ‘rosemary only grows when you don’t care about it’.
Of course, no plant at all grows well without the proper attention, but it does say something about the soil needs of rosemary.
Rosemary doesn’t like your overflowing attention, especially when it comes to watering. Once you know this, you can begin to see that this herb absolutely loves well-drained soil.
In fact, rosemary can quickly die in an over-moistened soil, which is understandable given that as a plant it originated in the dry sun of the Mediterranean.
Rosemary grows best when the soil surrounding its roots can trap a minimal amount of water and keep the air circulating smoothly underground.
Gardeners who grow rosemary outdoors will leave the plant without water for long periods of time in order to not suffocate the roots.
Generally speaking, rosemary does absolutely fine in gardens, although the soil there isn’t always the best.
That’s because outdoor gardens tend to have a very deep structure and are always exposed to the air, so water is never really trapped.
On the other hand, rosemary plants that are being grown in containers or pots are an entirely different story.
You simply can’t use that same garden soil in a pot with your rosemary and expect it to survive.
When you’re growing rosemary in pots, the first thing you need to do is to look after the drainage of the soil more extensively.
You also need to focus on how ‘rich’ the potting soil is; your rosemary can grow very slowly if the growing mix is devoid of the essential nutrients.
One important thing to know about rosemary is that it’s really quite flexible when it comes to the acidity of the soil it resides in.
It’s a little-known fact that rosemary can thrive in soil with a pH of anywhere between 6 and 8.
In the next section, I outline two great combinations or mixes that can work as a suitable potting soil for your rosemary.
The Ideal Soil for Rosemary:
The Standard Mix: 2/3 Regular Potting Soil + 1/3 Perlite
The simplest mix you can use is an adjusted regular potting soil, which is one of the most popular mixes for rosemary used by gardeners.
Any high-quality potting soil is usually well-drained but not enough for it to help grow drought-tolerant plants.
Growing rosemary in unmodified potting soil has decidedly mixed outcomes. The majority of gardeners fail to keep the herb alive when using regular potting soil alone, although there are others who have managed to have their rosemary thrive in such a soil.
Since regular potting soil tends to be inadequate on its own when it comes to keeping rosemary alive, gardeners prefer adding perlite to it.
The magic of perlite is hidden in its ability to flush excess water out, without being a hydrophobic material. A hydrophobic material is one that doesn’t let water enter in the first place, which is something you do not want for your rosemary.
Mixing one part perlite to two parts potting soil creates the standard mix that you can use to grow your rosemary.
I highly recommend using the famous Foxfarm Potting Soil.
The drawback of this mix:
One major drawback is that, depending on many factors – aside from the soil itself – this mix can sometimes fail to deliver the ideal drainage for rosemary.
That being said, it is possible to overcome such an issue – you can either add more perlite or reduce the number of times you water your rosemary.
An Alternative Mix For Stronger Drainage: ½ Cactus Soil + ½ Perlite:
Now, this may seem a bit unconventional to those who are just starting out but cactus soil, or the ‘cactus and succulent mix’, is widely used by experienced gardeners to cultivate a variety of herbs such as rosemary, sage, and thyme.
Cactus soil is made primarily for the cultivation of cacti and succulent plants in pots, such as aloe vera.
For that reason, such a mix is noted as being excellent for draining water.
Nevertheless, gardeners still prefer to add perlite to this mix, because it’s less harsh on their rosemary.
Perlite works to keep the roots well-aerated, and its water-draining capacity is moderate compared to the cactus soil.
If you do use this mix with your rosemary, you’ll never need to worry about water-drainage unless the soil becomes too old whilst in the pot.
Of course, you should always choose the best brand of cactus soil that you possibly can.
I usually use Hoffman’s Organic Cactus and Succulent Soil Mix and have always been satisfied enough to recommend it to others.
The drawback of this mix:
The main problem with this mix is that it may not be as rich in nutrients as high-quality potting soil.
Organic products that enrich the soil have water-trapping properties, and that’s why they’re not added in bulk to the ‘cactus and succulent’ mix.
Another issue that you may also face is that the soil might dry too fast, or at least faster than what your rosemary can keep up with.
In this event, you should add vermiculite or any other water-trapping material to the soil.
Important Things That You Should Know
The Use of Fertilisers
During your gardening journey you will naturally always need the assistance of fertilizers to grow your herbs, and this, of course, includes our queen, rosemary.
I would say that rosemary needs little to moderate amounts of fertilizers to grow well.
An evergreen herb such as this has all year to grow and is therefore not a huge nutrient consumer.
At the same time, almost all fertilizers are considered water-retaining, which unfortunately means they could negatively impact the drainage capacity of your soil if you were to add them in huge quantities.
If you are using Foxfarm – or any other nutrient-rich potting soil – you will need to forget about altering the soil with fertilizers for the first two or three months.
Afterward, or in other situations, you must use natural fertilizers to feed your herb. The best choice in my experience is a combination of vermicompost and other natural soil amendments of your choice.
Vermicompost, also known as ‘worm castings’, is a natural fertilizer that contains a high level of nitrogen, one of the most essential nutrients for proper plant growth.
The best worm castings found on the internet are without any doubt, Wiggle Worm Soil Builder Worm Castings.
Remember you must use soil amendments moderately, but even then don’t add more than one part of any fertilizer to two parts of your soil or mix.
The Drainage of Your Pot
Those who fail when it comes to growing rosemary can sometimes mistakenly assume that there’s a problem with the soil, when in fact the problem could be with the pot.
Pots that lack width and the proper draining holes can spell a big problem for your rosemary.
These kinds of pots usually trap water in a viscous way that immediately kills the herb.
I recommend that you always go for the highest quality of pots, or containers that are well-designed for draining water.
Don’t Forget to Repot
Repotting means changing the soil that your herb is growing in.
This is a very important activity that you should pay close attention to.
Every type of soil will change after they have been used for a finite period of time – usually months.
The change mainly affects the texture and nutrient composition of your soil. It will start to become less porous and empty of nutrients.
At that point, changing the soil is a must or else your rosemary’s health – and growth – will continue to decline.
Make changing the soil of your herb pots a routine every few months.
So, that’s all you need to know! You can now go forth and grow your rosemary. Don’t forget to share your thoughts and experiences in the comments below.