Putting rosemary outside is often a great idea as it can get a lot more sunlight than indoors, which will make it grow much faster and better. You have to do it right, though, and a crucial part of that is to do it at the right time of the year and only when the plant is ready for it.
The best time to put rosemary outside is in the spring approximately three weeks after the last frost. The plant must be at least 3 inches (7.6 cm) tall as it can otherwise be too fragile. Slightly larger plants generally have a higher survival rate, though, so waiting can be beneficial.
I wrote this article to try to answer any question you might have about when you should put your rosemary outside. So let’s get into it.
Best Time of the Year to Put Rosemary Outside
Perhaps the most important thing you need to consider if you are planning on transplanting your rosemary outside is if it is even the right time of the year to do so.
The ideal time to transplant rosemary outside is in the spring once there is no risk of frost. That way, the plant can grow outside for the longest possible amount of time before the winter, allowing it to get as large and strong as possible. Fall is also a good time to transplant rosemary outside if there is no frost for a few months.
I generally wait until at least three weeks after the last frost before I put mine outside. That seems to work really well.
I have written another article about the best time to transplant rosemary in which I go into much more detail.
Can You Put Rosemary Outside in Other Seasons Than Spring?
While spring is the best time to put rosemary outside, it is not the only option. So if you have a rosemary plant you want to put outside but it isn’t the ideal time of the year, you might still be able to.
The trick to putting rosemary outside in the summer is to avoid exposing it to too much sunlight right away. Instead, it should acclimate by staying outside for an increasing amount of time every day for 1-2 weeks before it can stay outside permanently.
Helping the plant acclimate is generally a good idea in the summer as there is often a big difference in the temperature and amount of sunlight in the new spot outside compared to the old spot inside.
Sometimes, it is even possible to put rosemary outside in the early fall if the weather is mild. If you do this, there should be no frost for at least three months to allow the plant and its roots to become well-established. Then when frost comes, protect the plant with a plant cover or similar.
It is only possible to transplant rosemary from indoors to outside in the winter in areas with no frost and some sunlight. Unless you live in a tropical area, I recommend waiting until spring. If you want to learn more about this, I have another article where I cover transplanting rosemary in the winter.
I like to start my rosemary from seed indoors in the winter as that gives it a couple of months to grow and become strong before it goes outside in the spring.
How to Tell if Your Rosemary Is Ready to Be Put Outside
If you put your rosemary outside before it is actually ready for it, there is a high risk it will not make it. We definitely don’t want that to happen after all the hard work we put in so far.
Rosemary should be at least 3 inches (about 7.5 cm) tall before being transplanted outside to reduce the risk of problems such as transplant shock.
I have seen the best results when I waited until the plant was about twice as tall as that, so about 6 inches (or about 15 cm). For me at least, it seems to be the sweet spot. Sure, it takes a bit longer but it also reduces the risk, so you have to determine what you prioritize.
So my seedlings from the photo above were not quite ready at that point, but they got ready within a month or so.
I have another article where I explain how you can know if your rosemary seedlings are ready to be transplanted in much more detail.
4 Things You MUST Remember Before Putting Rosemary Outside
While transplanting rosemary outside is not the most complicated task, there are a handful of essential things you should know.
I’ve come up with four crucial things you should consider before you put your rosemary outside.
- The temperature outside
- The amount of sunlight outside
- Whether your plant needs to acclimate
- If your plant has pests or is sick
Frost is probably what can kill a rosemary plant the fastest, so you have to consider the temperature outside. I recommend waiting until at least three weeks after the last frost.
There should also be enough sunlight. Ideally, rosemary should get eight hours per day on average, but less than that is fine in the beginning.
When you put your rosemary outside, chances are that it will experience a change in temperature and sunlight, so it probably needs to acclimate. I explain this in detail at the end of this article.
A mistake I have made before is to put plants outside that are suffering from a disease or being attacked by pests. It can be devastating to the surrounding plants if you place a sick or infected plant near them. I have another article where I discuss more mistakes people make when transplanting their rosemary and how you can avoid them.
It isn’t always easy to spot, but a clear sign something is wrong is that the foliage changes color or structure. Here is an example of how it can look.
If you have concluded that it is time to put your rosemary outside and you want it to be in the ground, I recommend heading over to my step-by-step guide on the best way to put rosemary in the ground.
Is It Better to Sow Rosemary Outside or Start It Indoors?
You can either start your rosemary inside and later move it outside (or just keep it inside) or you can sow it outside from the beginning. Both can work well, but in my experience, one method beats the others.
It seems to work best to start rosemary inside and move it outside later once it reaches a height of about 3-6 inches (about 7.5-15 cm). That way, it is less fragile when going outside, improving its chance of becoming established and growing well.
As I have already mentioned in this article, your rosemary might need to acclimate before you put it outside. I explain that now.
Best Way to Help Your Rosemary Acclimate
To acclimate essentially means to get used to a new environment. This can be necessary for rosemary when it is moved from one spot to another, especially if it goes from indoors to outside.
The primary reason acclimating is often needed is that the plant often experiences a significant change in environment. Primarily, in the temperature and amount of sunlight it gets.
Whether your rosemary will experience an increase or decrease in temperature and amount of sunlight, the technique is the same.
Put the plant outside for a few hours before bringing it back inside. The next day, put it outside for a few more hours than on the first day before bringing it back in. Continue this while gradually increasing the amount of time it stays outside over 1-2 weeks before leaving it outside permanently.
At this point, you can also plant it in the ground.