A single rosemary plant can reach about 5 feet (about 1.5 meters) in height and about 4 feet (about 1.2 meters) in width. Since it can spread by seed in warm climates, however, rosemary bushes can get extremely wide and might only be limited by their physical surroundings.
Even in a climate that does allow rosemary to reseed itself and spread that way, it happens slowly so it is easy to control.
Many factors affect how large a rosemary plant will get, so to get the best answer, I recommend that you keep reading this article as I will explain everything you should know.
In this article, I will explain what factors determine how large a rosemary plant will get as well as how you can control its size. That way, you know exactly what to do, regardless if you want your rosemary to get as large as possible or you want to keep it small.
How to Make Your Rosemary Plants Grow as Large as Possible
According to The Royal Horticulture Society, rosemary can reach 5 feet (1.5 meters) in height but that only happens under certain conditions.
Age is of course one of the most important factors that determines how large a rosemary plant is, but there are also other conditions that are at least as important.
If your goal is for your rosemary to get as large as possible, the most important things to know about are growing conditions, including sunlight, temperature, soil type, and more, and which variety of rosemary you grow as well as how much space it has. I will cover this in detail now.
If you haven’t already selected a variety, I recommend reading this article where I share 7 good varieties including information about plant size and more.
If you want to prevent your rosemary from getting too large, scroll a bit down as I explain the best way to do that a bit later in this article.
How growing conditions affect the size of rosemary plants
Sunlight, temperature, soil type, correct watering, and fertilizing are all factors that determine how well a plant will grow (or if it will grow at all).
Rosemary is a Mediterranean herb, which means it is naturally used to large amounts of direct sunlight, high temperatures, and low amounts of water.
The best way to help your rosemary grow as large as possible is to mimic the natural growing conditions as closely as possible. I made this table to give you an easy overview of the best growing conditions for rosemary.
|At least 6-8 hours per day
|68-86 F (20-30 C)
|In a pot: Weekly
In the ground: Every 2 weeks at most
|Every 1-2 months or never
|Loam (40% sand). Slightly acidic (6-7 pH)
These are the optimal growing conditions for rosemary and as such, the conditions you should aim for if you want your rosemary to get as large as possible. I have written another article, which you can find on this link, that I recommend reading if you want to learn more about this.
This is not only how an individual rosemary plant will grow best and get large but also how it is most likely to produce seeds that spread and sprout, ultimately making the overall rosemary bush wider and wider. That’s what happened to the rosemary in the photo at the beginning of this article.
Why spacing is important for how large rosemary can get
Rosemary that grows in the ground typically gets much larger than rosemary that grows in a pot or container. This usually happens even if the two plants get the exact same amount of sunlight and water and grow in the same type of soil.
The key difference is that the rosemary plant that grows in the ground has much more room for its roots to spread and grow whereas the root system for the rosemary plant growing in a pot, like mine in this photo, is limited.
This means that if you want your rosemary to get as large as possible, you should plant it in the ground rather than in a pot and if you want to keep it small, growing it in a small pot makes that easy. I recommend using terra cotta pots such as the ones on this link to Amazon. That’s what I always use for my potted garden plants including rosemary as you can see in the photo above.
You can read a lot more about the differences between growing rosemary in the ground and in a pot as well as the advantages and disadvantages of each method on this link.
Tallest and shortest rosemary varieties
The last factor that determines how large a rosemary plant can get that I want to cover is the variety of the plant.
According to this article, the tallest variety of rosemary is Tuscan Blue, so if your goal is to get the largest rosemary plant, get that variety and then consider planting a few of them near each other. At some point, they will grow large enough to appear as a single bush, standing both tall and wide.
If you want a rosemary plant that doesn’t get very tall, look into trailing varieties such as Blue Rain as they mostly “crawl” sideways or downwards rather than upwards like the one in this photo I took in Spain.
Easiest Way to Prevent Rosemary From Getting Too Large
If you don’t want your rosemary to get too large, I have a couple of simple tips for you that can make it much easier.
My first tip is to grow your rosemary in a pot or container instead of directly in the ground. As I explain earlier in this article, how much space the root system has plays a huge role in how large the plant can get. By keeping your rosemary in a pot, you limit the amount of space for the root system, thereby preventing the plant from getting too large.
As I mentioned briefly at the beginning of this article, rosemary can spread by reseeding itself (which you can learn more about here), although it usually doesn’t happen in my experience. If you want to be sure that it doesn’t happen, the best way to prevent it is to remove the flowers from your rosemary before the seeds mature.
The easiest way to do this is to remove the flowers as soon as they appear. That way, you are sure the seeds wont be mature enough to germinate. Just keep in mind that the flowers attract bees and other pollinators which are great for your garden, so you might not want to remove the flowers. I personally never remove them.
The last tip I want to give you if you don’t want your rosemary to get too large is that you can prune it to control its size (and shape) almost exactly as you want. There are actually multiple reasons why pruning your rosemary is a good idea and I recommend that you do it even if you don’t want to keep it small. You can read everything you need to know about it including the best way to prune rosemary on this link.