Although it is largely considered a herb by many—including me, of course—because of how it is commonly used for cooking, rosemary is not actually one. It’s a woody dwarf shrub that can be grown as a perennial. But developing woodiness too fast too soon can be a problem for the rosemary plant!
Rosemary can turn woody because of 1) natural aging, 2) lack of pruning, 3) excessive watering, 4) insufficient sun exposure, 5) frost damage, and 6) deterioration. Though woody growth is not necessarily bad, it can be a sign of serious problems like overwatering that could lead to the death of a rosemary plant.
The old woody parts of rosemary don’t produce new growth. So unless you can control it, thereby preventing it from becoming too woody, you may run out of fresh aromatic rosemary leaves to harvest! Keep reading to learn more!
1. Natural Aging
Because rosemary is a naturally bushy plant, its stems gradually become thick and woody at the base as it grows and ages. This is normal but can be prevented to avoid excessive development of old wood which doesn’t regrow or produce new leaves.
Technically speaking, virtually all plants that exist on Earth start their life as herbaceous little sprouts.
As its name suggests, herbs are plants that stay non-woody throughout their lifespan. They are also typically used for culinary and medicinal purposes. The latter definition applies to rosemary, but the former definitely doesn’t.
Stems and branches of rosemary subshrubs tend to get woody by the base as they grow. Nevertheless, they are widely considered a famous herb.
You see even though rosemary is an evergreen plant, it will no longer put out any of its fragrant and tasty leaves from its old woody stems.
Rosemary naturally becomes woodier with time to help it survive the dry and rocky environment of its native habitat—the Mediterranean. The thick woody layer protects it from drought, salt, and herbivores like deer. This also allows it to grow for years!
So if you leave it alone to grow as it wishes, it can grow wild in all directions. But keep in mind that more and more parts of its stem will turn woody this way.
To control the growth of a rosemary bush and keep it compact, regular harvesting and/or pruning are necessary. Doing so prevents the base of the plant from turning woody fast.
Don’t cut back to the old wood because you won’t get any new shoots growing out of that. It’s okay to only take about 4–6 inches from the top of a couple of stems each time.
Remember, the cut should happen on a soft and bending part of the stem. If you cut a woody part, that branch will remain dead.
Then you could either use that for dinner or propagate it in water or soil!
Curious? Learn how to grow plants in water now!
It’s also advisable to thin your older rosemary bushes from time to time. You can even give some of them away to friends and family after transferring them to their own pots.
2. Lack of Pruning
Not pruning rosemary regularly, even if done lightly, will result in woody overgrowth that will spread up the stems and branches of the plant. Thus, pruning is the main way to prevent rosemary from becoming woody.
Actually, this is somewhat similar to the previous reason. When you don’t prune your rosemary subshrub, it’s bound to get bushy and taller, right?
Of course, this also means that rosemary that isn’t pruned regularly—if at all—will develop thick and woody growth upward from its very base.
With time, you’ll notice how it starts growing thicker and woodier. That woodiness will keep extending until you get less and less green growth from the lower half of your rosemary!
This is normal when a naturally woody plant like rosemary grows excessively, especially if you’ve already sparingly fed it some high-quality water-soluble fertilizer.
Home gardeners can keep their rosemary from becoming too woody by lightly pruning it from the tip down to the green and light brown portion of the stem as needed. Start doing this around spring to encourage green growth.
Then, hard-pruning it down to about 1/4 or 1/3 once a year also helps make it more manageable. But, again, never completely chop it down to its bare old woody stems and stalks. Always make sure to leave behind some brown but non-woody growing stems.
Otherwise, your rosemary may never come back again and you’ll have to start all over!
3. Excessive Watering
When overwatered for a long time, dwarf rosemary shrubs can grow woody or simply die for lack of oxygen at the root level. Browning of its needle-like leaves is another sign of excessive watering.
One thing that not a lot of people seem to know is that improper watering, specifically overwatering, can indeed cause an overgrowth of woody stems and stalks in rosemary.
Also, it’s important to keep in mind that rosemary thrives with only low to moderate watering.
Established, well-rooted rosemary bushes, in particular, are very resistant to drought. This, however, also means that they are more susceptible to root rot.
Native to the Mediterranean region, the inherent woodiness of rosemary allows it to grow well even in dry and rocky shallow soils.
Remember as well that damage from excess watering can lead to significant plant decline. It may even die from too much water—but more on that later on.
It is better to err on the side of underwatering than overwatering when talking about rosemary. Water it sparingly and allow its soil to dry between watering.
Remember, the best way to grow a plant, rosemary included is to remember where it comes from. Rosemary is a Mediterranean plant used to dry environments.
Provide about an inch of water per rosemary shrub every 1–2 weeks. On really hot summer days, they can be watered more frequently.
Check the composition of its soil as well. If it stays too wet for too long, I would advise you to add other growing mediums like sand and perlite. This improves the texture and ensures proper drainage.
Learn the difference between your options in our article on growing medium for plants!
Double-check the pot’s drainage holes too. If it only has 1 tiny hole, you could either transfer it to another pot with more holes or add holes to its existing container.
4. Insufficient Sun Exposure
Non-herbaceous plants like rosemary will develop more woodiness as it grows taller, especially when it doesn’t get enough full sun exposure. Ideally, it should receive about 6 hours of direct sunlight every day. It can survive with less, especially in winter but it will not grow vigorously.
Giving rosemary plants too much water, too often, will also result in rank growth or dense but thin subshrub development in these woody plants.
This results in unfavorable shading for the stems and leaves that are hidden deep within the rosemary bush, which now brings us to the 4th possible cause of woody growth in rosemary.
Here’s the thing, just like trees, rosemary will produce longer and thicker stems that become woody over time. It helps it compete with other nearby plants that are placing it in the shade.
By growing taller and woodier compared to the plants around it, rosemary can spread out its branches more and produce dense foliage to capture more sunlight.
If you’re growing your rosemary outdoors in a north or east-facing garden, you’re likely to experience this.
Provide sufficient sunlight or supplement it with a grow light if grown indoors (like the one below from Amazon) if you’re growing your rosemary in a pot indoors.
They also do great near south and southwest-facing windows in the house.
Rosemary grows best with at least 6 hours of full sun exposure. Grown inside the house, it can be placed 6–12 inches (15–30 cm) under a grow light that’s at least 20W for more or less 12–14 hours daily.
5. Frost Damage
A rosemary plant exposed to harsh fall and winter weather is highly likely to sustain cold or frost damage and develop woodier stems to protect itself. Its stem tips and leave will also turn dark and appear woody.
For the most part, rosemary is grown as an annual in zones 1–7 in the United States such as West Virginia.
But even perennial rosemary shrubs grown within zones 8–11, like Los Angeles, are invincible to weather extremes.
While it is somewhat frost-tolerant, prolonged exposure to freezing temperatures outdoors—especially during frost—can be very detrimental for rosemary even if it becomes dormant.
Your rosemary bush may not survive outside when temperatures constantly dip below 27°F (3°C). That’s just too cold for most rosemary varieties.
Leaves of cold or frost-damaged rosemary will turn brown or black and curly, making the dwarf shrub look much more woody than normal. Even their tender green tips may become discolored.
Unfortunately, you can’t fix woody rosemary if the damage was done by frost and low temperatures. Rosemary grows best with temperatures within 42–75°F (6–24°C).
Instead, they can be overwintered indoors so you won’t have to plant them again or buy a new one from the nursery in the coming season.
But make sure to carefully and gradually harden off your rosemary. Don’t bring it straight indoors from your garden as it may not survive the sudden drastic change in its environment.
An old and deteriorating rosemary bush may look as if it has become excessively woody due to the darkening of its dying stems and leaves. Deadwood commonly accumulates in the center of big and old rosemary subshrubs.
If you’re wondering whether a woody rosemary can be saved, I’ve got you!
A woody rosemary subshrub can generally be saved as long as it still has some green growth and it hasn’t been cut down to only its old wood stems at the very base.
With more growing medium and space at its disposal, rosemary can quickly grow dense. The stems and branches by their base can easily grow very thick and woody.
Partially prune rosemary bushes, especially upright varieties, to the base by the lower center portion and completely pull out old wood branches with no growing stem sections on them. You can do this around mid-summer.
In doing so, you can help prevent starting a fire since the accumulation of deadwood can easily catch fire. This is especially true for oil-rich Mediterranean herbs like rosemary.
Don’t worry, though—those won’t go to waste as long as they aren’t infested with pests. Even if they aren’t edible, the tough old wood from rosemary can be used for aromatic skewers and smoking meats.
How do you prune a woody rosemary bush?
When pruning rosemary shrubs, there are two methods: 1) tip-shearing and 2) hard-pruning. Tips shearing can be done starting all year round for fuller growth as needed but the rosemary should be allowed to regrow in between. Hard-pruning early in spring with loppers or a pruning saw is advised to stimulate new green growth for the season.
Is it possible to turn woody rosemary stems green again?
It is not possible to turn brown and woody rosemary stems green again as the herb naturally only grows new shoots from the tips of its younger, tender, green stems. Even annual hard-pruning can’t stop the woody part from extending up the plant but such practice will greatly slow it down.
Summary of Why Rosemary Turns Woody
Dwarf shrubs of Rosemary can develop excessively woody stems due to natural aging, not pruning enough or at all, overwatering, lack of full sun exposure, damage from cold or frost, and plant deterioration.
In other words, woody growth on rosemary is not necessarily a problem. However, excessive thickness and woodiness may be a sign of issues with watering, light exposure, and temperatures. Such unfavorable growing factors must be addressed promptly to prevent the plant from dying completely.
- “Rosemary” by Peggy Dierking in the University of Arizona
- “Rosemary” by Polly Nelson in Agriculture and Natural Resources, University of California
- “Rosemary” by n/a in PlantVillage
- “Salvia rosmarinus” by n/a in N.C. Cooperative Extension
- “Environmental Disorders of Woody Plants” by C.E. Swift, W.R. Jacobi, M. Schomaker, and D.A. Leatherman in Colorado State University Extension
- “How Woody Plants Grow” by Pyan Panaku in Illinois Extension
- “Growing Herbs” by Kerry Smith and Wendy Ulrich in the Alabama Cooperative Extension System