Whether your rosemary plant doesn’t seem to be growing or your seeds aren’t germinating, you have come to the right place. I have dealt with both of those problems before and I have also had friends come to me and ask about them, so I have done a lot of research and testing to figure it out.
I learned that while there are several potential reasons why rosemary sometimes doesn’t grow, the problem is surprisingly often the same and not that difficult to solve.
In this article, I first cover the 5 most likely reasons why rosemary plants sometimes stop growing as well as what you should do about it and then the 6 most likely reasons why the seeds sometimes won’t germinate.
5 Reasons Why Your Rosemary Plant Is Not Growing
Rosemary is a perennial herb that can grow for many years under the right conditions, but there are several things that can cause it to stop growing. I cover the 5 most likely reasons why that happens below.
1. Your Rosemary Has Become Rootbound
I wanted to mention this issue first because I have seen it so many times before. People come to me and ask what is wrong with their potted rosemary and the issue is surprisingly often that it just doesn’t have enough space. This is, of course, much more likely to happen to potted rosemary than rosemary growing in the ground.
Potted rosemary will eventually run out of room for the roots to grow unless it is growing in a massive pot. If that happens, the roots will no longer be able to obtain water and nutrients, which causes the plant to stop growing.
The solution to this problem is very simple. You just have to transplant your rosemary to a larger pot or into the ground where the roots have room to grow. I have a guide where I explain how to do that on this link.
2. Incorrect Watering
The second most common problem I have seen that causes rosemary to stop growing is incorrect watering. Overwatering specifically is a common mistake people make when they grow rosemary.
This is because rosemary doesn’t need a lot of water and because the first signs of overwatering easily can be mistaken and interpreted as the plant needing more water.
I have written a guide on how to water rosemary correctly depending on how and where you grow it, how large it is, and more. You can find the guide on this link.
3. Your Rosemary Is Flowering
Like most other herbs, rosemary will eventually flower and when that happens, the energy is diverted toward flowering rather than toward growing. This means that rosemary typically stops growing, or at least grows much slower, when it is flowering, so if your is, that is most likely why it isn’t growing right now. It will resume growing once it stops flowering if this is the reason.
You don’t necessarily have to do anything when your rosemary is flowering but you can sometimes stop the flowering process by removing the flowers, which essentially forces the plant to start growing again. You can read more about that in the article on this link.
I usually don’t do that, though, but let it flower instead. You can still harvest from it and the flowers are even edible but will also attract beneficial insects to your garden if you leave them on the plant.
4. Your Rosemary Is Not Getting Enough Sunlight
As a native to the Mediterranean region, rosemary needs a lot of sunlight to grow and thrive. Ideally 6-8 hours of sunlight per day. It can often survive with much less than that, but it will impact its growth significantly. The less sunlight rosemary gets, the slower it will grow.
I have another article where I go more into detail about how much sunlight rosemary needs and what you can do to help it. I also cover other growing conditions such as spacing, soil type, nutrients, and other things that can affect its growth. You can find the article on this link.
5. The Temperature Is Too Low
In addition to a lot of sunlight, rosemary also grows best in high temperatures. It can survive pretty cold weather as long as the roots don’t freeze, but since they are protected by a layer of soil, the plant will usually survive temperatures that are slightly below the freezing point.
Rosemary will, however, grow significantly slower or even stop growing entirely when it gets too cold.
If it is winter or winter is coming up, that could very well be why your rosemary is not growing right now. If that is the case, I highly recommend that you head over to the article on this link, where I explain how to help your rosemary survive the winter.
6 Reasons Why Your Rosemary Seeds Are Not Germinating
Rosemary seeds can take up to a month to germinate, which is significantly longer than many other garden plants. If you have waited for a month and the seeds still haven’t sprouted, you are most likely having one of the problems I cover now.
1. Incorrect watering
It is very easy to damage seeds before they sprout by watering them incorrectly.
Too much water can lead to a lack of oxygen, which can potentially prevent the seed from germinating and too little water or too infrequent watering can cause it to dry out and die before it sprouts and breaks through the soil.
If you suspect that this is why your seeds aren’t sprouting, you should sow some new seeds and water them as often as it takes to keep the soil consistently moist without drying out or getting too soggy. I find that this is easiest to achieve by watering in small but frequent doses.
2. Your Rosemary Seeds Are Too Old
The most common reason why my seeds, rosemary or otherwise, sometimes don’t germinate is that they are too old.
According to this wonderful seed storage guide from Johnny’s Selected Seeds, rosemary seeds can last between 1-4 years.
Seed germination rates drop over time, so if yours are older than those 1-4 years, that is most likely why they aren’t germinating.
3. Your Rosemary Seeds Were Damaged From Incorrect Storage
Rosemary seeds can last for several years if stored correctly, but if they are exposed to moisture, frost, or too much light, they can easily become damaged to a point where they won’t germinate.
The best way to store them is in a dark, dry, and relatively cold (although not freezing) place. The better they are stored, the longer they will last.
4. Your Rosemary Seeds Were Sown Too Deep
If seeds are sown too deep, there is a risk that they will never sprout since it takes them too long to break through the soil. Rosemary seeds should be sown about a ¼-½ inch (about ½-1 cm) deep.
If you suspect that you might have planted your seeds too deep, it is best to just sow some new seeds and make sure they aren’t too deep.
I have another article where I explain everything you should know when sowing rosemary seeds to avoid problems. You can find the article by clicking on this link.
5. The Soil Temperature Is Too Low
If the soil is too cold, your rosemary seeds are not going to germinate. According to this article from University of Massachusetts Amherst, the best soil temperature for rosemary seeds to germinate is 60° F (about 15.5° C).
Higher temperatures generally mean faster germination and lower temperatures generally mean slower germination.
I usually grow rosemary from cuttings rather than from seed, but the times I have started it from seed, I sowed it in small pots indoors. I recommend you do this too since it is easier to keep the soil warm enough that way.
6. Your Rosemary Seeds Have Been Eaten by Pests
The last reason why your rosemary seeds might not be sprouting is that they have been eaten by pests. This is, of course, much more likely to happen outside than indoors and also more likely to happen if you have sowed the seeds directly in the ground rather than in a pot, but it can happen regardless.
The best way to avoid this issue is to sow your rosemary seeds in some small pots indoors and keep them in a sunny spot until they are large enough to be planted outside. The bigger the plants are, the less likely they are to be eaten entirely by pests.